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2485 lines
70 KiB
C
2485 lines
70 KiB
C
/*
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* fs/fs-writeback.c
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*
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* Copyright (C) 2002, Linus Torvalds.
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*
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* Contains all the functions related to writing back and waiting
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* upon dirty inodes against superblocks, and writing back dirty
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* pages against inodes. ie: data writeback. Writeout of the
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* inode itself is not handled here.
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*
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* 10Apr2002 Andrew Morton
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* Split out of fs/inode.c
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* Additions for address_space-based writeback
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*/
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#include <linux/kernel.h>
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#include <linux/export.h>
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#include <linux/spinlock.h>
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#include <linux/slab.h>
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#include <linux/sched.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/pagemap.h>
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#include <linux/kthread.h>
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#include <linux/writeback.h>
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#include <linux/blkdev.h>
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#include <linux/backing-dev.h>
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#include <linux/tracepoint.h>
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#include <linux/device.h>
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#include <linux/memcontrol.h>
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#include "internal.h"
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/*
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* 4MB minimal write chunk size
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*/
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#define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_SHIFT - 10))
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struct wb_completion {
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atomic_t cnt;
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};
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/*
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* Passed into wb_writeback(), essentially a subset of writeback_control
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*/
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struct wb_writeback_work {
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long nr_pages;
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struct super_block *sb;
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unsigned long *older_than_this;
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enum writeback_sync_modes sync_mode;
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unsigned int tagged_writepages:1;
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unsigned int for_kupdate:1;
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unsigned int range_cyclic:1;
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unsigned int for_background:1;
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unsigned int for_sync:1; /* sync(2) WB_SYNC_ALL writeback */
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unsigned int auto_free:1; /* free on completion */
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enum wb_reason reason; /* why was writeback initiated? */
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struct list_head list; /* pending work list */
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struct wb_completion *done; /* set if the caller waits */
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};
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/*
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* If one wants to wait for one or more wb_writeback_works, each work's
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* ->done should be set to a wb_completion defined using the following
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* macro. Once all work items are issued with wb_queue_work(), the caller
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* can wait for the completion of all using wb_wait_for_completion(). Work
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* items which are waited upon aren't freed automatically on completion.
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*/
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#define DEFINE_WB_COMPLETION_ONSTACK(cmpl) \
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struct wb_completion cmpl = { \
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.cnt = ATOMIC_INIT(1), \
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}
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/*
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* If an inode is constantly having its pages dirtied, but then the
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* updates stop dirtytime_expire_interval seconds in the past, it's
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* possible for the worst case time between when an inode has its
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* timestamps updated and when they finally get written out to be two
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* dirtytime_expire_intervals. We set the default to 12 hours (in
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* seconds), which means most of the time inodes will have their
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* timestamps written to disk after 12 hours, but in the worst case a
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* few inodes might not their timestamps updated for 24 hours.
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*/
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unsigned int dirtytime_expire_interval = 12 * 60 * 60;
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static inline struct inode *wb_inode(struct list_head *head)
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{
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return list_entry(head, struct inode, i_io_list);
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}
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/*
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* Include the creation of the trace points after defining the
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* wb_writeback_work structure and inline functions so that the definition
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* remains local to this file.
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*/
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#define CREATE_TRACE_POINTS
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#include <trace/events/writeback.h>
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EXPORT_TRACEPOINT_SYMBOL_GPL(wbc_writepage);
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static bool wb_io_lists_populated(struct bdi_writeback *wb)
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{
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if (wb_has_dirty_io(wb)) {
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return false;
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} else {
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set_bit(WB_has_dirty_io, &wb->state);
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WARN_ON_ONCE(!wb->avg_write_bandwidth);
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atomic_long_add(wb->avg_write_bandwidth,
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&wb->bdi->tot_write_bandwidth);
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return true;
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}
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}
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static void wb_io_lists_depopulated(struct bdi_writeback *wb)
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{
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if (wb_has_dirty_io(wb) && list_empty(&wb->b_dirty) &&
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list_empty(&wb->b_io) && list_empty(&wb->b_more_io)) {
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clear_bit(WB_has_dirty_io, &wb->state);
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WARN_ON_ONCE(atomic_long_sub_return(wb->avg_write_bandwidth,
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&wb->bdi->tot_write_bandwidth) < 0);
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}
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}
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/**
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* inode_io_list_move_locked - move an inode onto a bdi_writeback IO list
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* @inode: inode to be moved
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* @wb: target bdi_writeback
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* @head: one of @wb->b_{dirty|io|more_io|dirty_time}
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*
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* Move @inode->i_io_list to @list of @wb and set %WB_has_dirty_io.
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* Returns %true if @inode is the first occupant of the !dirty_time IO
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* lists; otherwise, %false.
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*/
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static bool inode_io_list_move_locked(struct inode *inode,
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struct bdi_writeback *wb,
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struct list_head *head)
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{
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assert_spin_locked(&wb->list_lock);
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list_move(&inode->i_io_list, head);
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/* dirty_time doesn't count as dirty_io until expiration */
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if (head != &wb->b_dirty_time)
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return wb_io_lists_populated(wb);
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wb_io_lists_depopulated(wb);
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return false;
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}
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/**
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* inode_io_list_del_locked - remove an inode from its bdi_writeback IO list
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* @inode: inode to be removed
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* @wb: bdi_writeback @inode is being removed from
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*
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* Remove @inode which may be on one of @wb->b_{dirty|io|more_io} lists and
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* clear %WB_has_dirty_io if all are empty afterwards.
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*/
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static void inode_io_list_del_locked(struct inode *inode,
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struct bdi_writeback *wb)
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{
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assert_spin_locked(&wb->list_lock);
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list_del_init(&inode->i_io_list);
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wb_io_lists_depopulated(wb);
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}
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static void wb_wakeup(struct bdi_writeback *wb)
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{
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spin_lock_bh(&wb->work_lock);
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if (test_bit(WB_registered, &wb->state))
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mod_delayed_work(bdi_wq, &wb->dwork, 0);
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spin_unlock_bh(&wb->work_lock);
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}
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static void finish_writeback_work(struct bdi_writeback *wb,
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struct wb_writeback_work *work)
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{
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struct wb_completion *done = work->done;
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if (work->auto_free)
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kfree(work);
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if (done && atomic_dec_and_test(&done->cnt))
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wake_up_all(&wb->bdi->wb_waitq);
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}
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static void wb_queue_work(struct bdi_writeback *wb,
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struct wb_writeback_work *work)
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{
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trace_writeback_queue(wb, work);
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if (work->done)
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atomic_inc(&work->done->cnt);
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spin_lock_bh(&wb->work_lock);
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if (test_bit(WB_registered, &wb->state)) {
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list_add_tail(&work->list, &wb->work_list);
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mod_delayed_work(bdi_wq, &wb->dwork, 0);
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} else
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finish_writeback_work(wb, work);
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spin_unlock_bh(&wb->work_lock);
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}
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/**
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* wb_wait_for_completion - wait for completion of bdi_writeback_works
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* @bdi: bdi work items were issued to
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* @done: target wb_completion
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*
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* Wait for one or more work items issued to @bdi with their ->done field
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* set to @done, which should have been defined with
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* DEFINE_WB_COMPLETION_ONSTACK(). This function returns after all such
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* work items are completed. Work items which are waited upon aren't freed
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* automatically on completion.
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*/
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static void wb_wait_for_completion(struct backing_dev_info *bdi,
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struct wb_completion *done)
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{
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atomic_dec(&done->cnt); /* put down the initial count */
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wait_event(bdi->wb_waitq, !atomic_read(&done->cnt));
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}
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#ifdef CONFIG_CGROUP_WRITEBACK
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/* parameters for foreign inode detection, see wb_detach_inode() */
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#define WB_FRN_TIME_SHIFT 13 /* 1s = 2^13, upto 8 secs w/ 16bit */
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#define WB_FRN_TIME_AVG_SHIFT 3 /* avg = avg * 7/8 + new * 1/8 */
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#define WB_FRN_TIME_CUT_DIV 2 /* ignore rounds < avg / 2 */
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#define WB_FRN_TIME_PERIOD (2 * (1 << WB_FRN_TIME_SHIFT)) /* 2s */
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#define WB_FRN_HIST_SLOTS 16 /* inode->i_wb_frn_history is 16bit */
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#define WB_FRN_HIST_UNIT (WB_FRN_TIME_PERIOD / WB_FRN_HIST_SLOTS)
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/* each slot's duration is 2s / 16 */
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#define WB_FRN_HIST_THR_SLOTS (WB_FRN_HIST_SLOTS / 2)
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/* if foreign slots >= 8, switch */
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#define WB_FRN_HIST_MAX_SLOTS (WB_FRN_HIST_THR_SLOTS / 2 + 1)
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/* one round can affect upto 5 slots */
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static atomic_t isw_nr_in_flight = ATOMIC_INIT(0);
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static struct workqueue_struct *isw_wq;
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void __inode_attach_wb(struct inode *inode, struct page *page)
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{
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struct backing_dev_info *bdi = inode_to_bdi(inode);
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struct bdi_writeback *wb = NULL;
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if (inode_cgwb_enabled(inode)) {
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struct cgroup_subsys_state *memcg_css;
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if (page) {
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memcg_css = mem_cgroup_css_from_page(page);
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wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
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} else {
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/* must pin memcg_css, see wb_get_create() */
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memcg_css = task_get_css(current, memory_cgrp_id);
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wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
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css_put(memcg_css);
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}
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}
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if (!wb)
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wb = &bdi->wb;
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/*
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* There may be multiple instances of this function racing to
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* update the same inode. Use cmpxchg() to tell the winner.
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*/
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if (unlikely(cmpxchg(&inode->i_wb, NULL, wb)))
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wb_put(wb);
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}
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/**
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* locked_inode_to_wb_and_lock_list - determine a locked inode's wb and lock it
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* @inode: inode of interest with i_lock held
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*
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* Returns @inode's wb with its list_lock held. @inode->i_lock must be
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* held on entry and is released on return. The returned wb is guaranteed
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* to stay @inode's associated wb until its list_lock is released.
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*/
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static struct bdi_writeback *
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locked_inode_to_wb_and_lock_list(struct inode *inode)
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__releases(&inode->i_lock)
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__acquires(&wb->list_lock)
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{
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while (true) {
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struct bdi_writeback *wb = inode_to_wb(inode);
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/*
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* inode_to_wb() association is protected by both
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* @inode->i_lock and @wb->list_lock but list_lock nests
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* outside i_lock. Drop i_lock and verify that the
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* association hasn't changed after acquiring list_lock.
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*/
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wb_get(wb);
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spin_unlock(&inode->i_lock);
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spin_lock(&wb->list_lock);
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/* i_wb may have changed inbetween, can't use inode_to_wb() */
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if (likely(wb == inode->i_wb)) {
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wb_put(wb); /* @inode already has ref */
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return wb;
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}
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spin_unlock(&wb->list_lock);
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wb_put(wb);
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cpu_relax();
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spin_lock(&inode->i_lock);
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}
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}
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/**
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* inode_to_wb_and_lock_list - determine an inode's wb and lock it
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* @inode: inode of interest
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*
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* Same as locked_inode_to_wb_and_lock_list() but @inode->i_lock isn't held
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* on entry.
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*/
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static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode)
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__acquires(&wb->list_lock)
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{
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spin_lock(&inode->i_lock);
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return locked_inode_to_wb_and_lock_list(inode);
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}
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struct inode_switch_wbs_context {
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struct inode *inode;
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struct bdi_writeback *new_wb;
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struct rcu_head rcu_head;
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struct work_struct work;
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};
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static void inode_switch_wbs_work_fn(struct work_struct *work)
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{
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struct inode_switch_wbs_context *isw =
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container_of(work, struct inode_switch_wbs_context, work);
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struct inode *inode = isw->inode;
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struct address_space *mapping = inode->i_mapping;
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struct bdi_writeback *old_wb = inode->i_wb;
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struct bdi_writeback *new_wb = isw->new_wb;
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XA_STATE(xas, &mapping->i_pages, 0);
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struct page *page;
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bool switched = false;
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/*
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* By the time control reaches here, RCU grace period has passed
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* since I_WB_SWITCH assertion and all wb stat update transactions
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* between unlocked_inode_to_wb_begin/end() are guaranteed to be
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* synchronizing against the i_pages lock.
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*
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* Grabbing old_wb->list_lock, inode->i_lock and the i_pages lock
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* gives us exclusion against all wb related operations on @inode
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* including IO list manipulations and stat updates.
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*/
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if (old_wb < new_wb) {
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spin_lock(&old_wb->list_lock);
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spin_lock_nested(&new_wb->list_lock, SINGLE_DEPTH_NESTING);
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} else {
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spin_lock(&new_wb->list_lock);
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spin_lock_nested(&old_wb->list_lock, SINGLE_DEPTH_NESTING);
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}
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spin_lock(&inode->i_lock);
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xa_lock_irq(&mapping->i_pages);
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/*
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* Once I_FREEING is visible under i_lock, the eviction path owns
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* the inode and we shouldn't modify ->i_io_list.
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*/
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if (unlikely(inode->i_state & I_FREEING))
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goto skip_switch;
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/*
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* Count and transfer stats. Note that PAGECACHE_TAG_DIRTY points
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* to possibly dirty pages while PAGECACHE_TAG_WRITEBACK points to
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* pages actually under writeback.
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*/
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xas_for_each_marked(&xas, page, ULONG_MAX, PAGECACHE_TAG_DIRTY) {
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if (PageDirty(page)) {
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dec_wb_stat(old_wb, WB_RECLAIMABLE);
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inc_wb_stat(new_wb, WB_RECLAIMABLE);
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}
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}
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xas_set(&xas, 0);
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xas_for_each_marked(&xas, page, ULONG_MAX, PAGECACHE_TAG_WRITEBACK) {
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WARN_ON_ONCE(!PageWriteback(page));
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dec_wb_stat(old_wb, WB_WRITEBACK);
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inc_wb_stat(new_wb, WB_WRITEBACK);
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}
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wb_get(new_wb);
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/*
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* Transfer to @new_wb's IO list if necessary. The specific list
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* @inode was on is ignored and the inode is put on ->b_dirty which
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* is always correct including from ->b_dirty_time. The transfer
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* preserves @inode->dirtied_when ordering.
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*/
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if (!list_empty(&inode->i_io_list)) {
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struct inode *pos;
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inode_io_list_del_locked(inode, old_wb);
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inode->i_wb = new_wb;
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list_for_each_entry(pos, &new_wb->b_dirty, i_io_list)
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if (time_after_eq(inode->dirtied_when,
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pos->dirtied_when))
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break;
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inode_io_list_move_locked(inode, new_wb, pos->i_io_list.prev);
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} else {
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inode->i_wb = new_wb;
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}
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/* ->i_wb_frn updates may race wbc_detach_inode() but doesn't matter */
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inode->i_wb_frn_winner = 0;
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inode->i_wb_frn_avg_time = 0;
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inode->i_wb_frn_history = 0;
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switched = true;
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skip_switch:
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/*
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* Paired with load_acquire in unlocked_inode_to_wb_begin() and
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* ensures that the new wb is visible if they see !I_WB_SWITCH.
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*/
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smp_store_release(&inode->i_state, inode->i_state & ~I_WB_SWITCH);
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xa_unlock_irq(&mapping->i_pages);
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spin_unlock(&inode->i_lock);
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spin_unlock(&new_wb->list_lock);
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spin_unlock(&old_wb->list_lock);
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if (switched) {
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wb_wakeup(new_wb);
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wb_put(old_wb);
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}
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wb_put(new_wb);
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iput(inode);
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kfree(isw);
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atomic_dec(&isw_nr_in_flight);
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}
|
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|
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static void inode_switch_wbs_rcu_fn(struct rcu_head *rcu_head)
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{
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struct inode_switch_wbs_context *isw = container_of(rcu_head,
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struct inode_switch_wbs_context, rcu_head);
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|
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/* needs to grab bh-unsafe locks, bounce to work item */
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INIT_WORK(&isw->work, inode_switch_wbs_work_fn);
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queue_work(isw_wq, &isw->work);
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}
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|
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/**
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* inode_switch_wbs - change the wb association of an inode
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* @inode: target inode
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* @new_wb_id: ID of the new wb
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*
|
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* Switch @inode's wb association to the wb identified by @new_wb_id. The
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* switching is performed asynchronously and may fail silently.
|
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*/
|
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static void inode_switch_wbs(struct inode *inode, int new_wb_id)
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{
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struct backing_dev_info *bdi = inode_to_bdi(inode);
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struct cgroup_subsys_state *memcg_css;
|
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struct inode_switch_wbs_context *isw;
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|
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/* noop if seems to be already in progress */
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if (inode->i_state & I_WB_SWITCH)
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return;
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|
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isw = kzalloc(sizeof(*isw), GFP_ATOMIC);
|
|
if (!isw)
|
|
return;
|
|
|
|
/* find and pin the new wb */
|
|
rcu_read_lock();
|
|
memcg_css = css_from_id(new_wb_id, &memory_cgrp_subsys);
|
|
if (memcg_css)
|
|
isw->new_wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
|
|
rcu_read_unlock();
|
|
if (!isw->new_wb)
|
|
goto out_free;
|
|
|
|
/* while holding I_WB_SWITCH, no one else can update the association */
|
|
spin_lock(&inode->i_lock);
|
|
if (!(inode->i_sb->s_flags & SB_ACTIVE) ||
|
|
inode->i_state & (I_WB_SWITCH | I_FREEING) ||
|
|
inode_to_wb(inode) == isw->new_wb) {
|
|
spin_unlock(&inode->i_lock);
|
|
goto out_free;
|
|
}
|
|
inode->i_state |= I_WB_SWITCH;
|
|
__iget(inode);
|
|
spin_unlock(&inode->i_lock);
|
|
|
|
isw->inode = inode;
|
|
|
|
atomic_inc(&isw_nr_in_flight);
|
|
|
|
/*
|
|
* In addition to synchronizing among switchers, I_WB_SWITCH tells
|
|
* the RCU protected stat update paths to grab the i_page
|
|
* lock so that stat transfer can synchronize against them.
|
|
* Let's continue after I_WB_SWITCH is guaranteed to be visible.
|
|
*/
|
|
call_rcu(&isw->rcu_head, inode_switch_wbs_rcu_fn);
|
|
return;
|
|
|
|
out_free:
|
|
if (isw->new_wb)
|
|
wb_put(isw->new_wb);
|
|
kfree(isw);
|
|
}
|
|
|
|
/**
|
|
* wbc_attach_and_unlock_inode - associate wbc with target inode and unlock it
|
|
* @wbc: writeback_control of interest
|
|
* @inode: target inode
|
|
*
|
|
* @inode is locked and about to be written back under the control of @wbc.
|
|
* Record @inode's writeback context into @wbc and unlock the i_lock. On
|
|
* writeback completion, wbc_detach_inode() should be called. This is used
|
|
* to track the cgroup writeback context.
|
|
*/
|
|
void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
|
|
struct inode *inode)
|
|
{
|
|
if (!inode_cgwb_enabled(inode)) {
|
|
spin_unlock(&inode->i_lock);
|
|
return;
|
|
}
|
|
|
|
wbc->wb = inode_to_wb(inode);
|
|
wbc->inode = inode;
|
|
|
|
wbc->wb_id = wbc->wb->memcg_css->id;
|
|
wbc->wb_lcand_id = inode->i_wb_frn_winner;
|
|
wbc->wb_tcand_id = 0;
|
|
wbc->wb_bytes = 0;
|
|
wbc->wb_lcand_bytes = 0;
|
|
wbc->wb_tcand_bytes = 0;
|
|
|
|
wb_get(wbc->wb);
|
|
spin_unlock(&inode->i_lock);
|
|
|
|
/*
|
|
* A dying wb indicates that the memcg-blkcg mapping has changed
|
|
* and a new wb is already serving the memcg. Switch immediately.
|
|
*/
|
|
if (unlikely(wb_dying(wbc->wb)))
|
|
inode_switch_wbs(inode, wbc->wb_id);
|
|
}
|
|
|
|
/**
|
|
* wbc_detach_inode - disassociate wbc from inode and perform foreign detection
|
|
* @wbc: writeback_control of the just finished writeback
|
|
*
|
|
* To be called after a writeback attempt of an inode finishes and undoes
|
|
* wbc_attach_and_unlock_inode(). Can be called under any context.
|
|
*
|
|
* As concurrent write sharing of an inode is expected to be very rare and
|
|
* memcg only tracks page ownership on first-use basis severely confining
|
|
* the usefulness of such sharing, cgroup writeback tracks ownership
|
|
* per-inode. While the support for concurrent write sharing of an inode
|
|
* is deemed unnecessary, an inode being written to by different cgroups at
|
|
* different points in time is a lot more common, and, more importantly,
|
|
* charging only by first-use can too readily lead to grossly incorrect
|
|
* behaviors (single foreign page can lead to gigabytes of writeback to be
|
|
* incorrectly attributed).
|
|
*
|
|
* To resolve this issue, cgroup writeback detects the majority dirtier of
|
|
* an inode and transfers the ownership to it. To avoid unnnecessary
|
|
* oscillation, the detection mechanism keeps track of history and gives
|
|
* out the switch verdict only if the foreign usage pattern is stable over
|
|
* a certain amount of time and/or writeback attempts.
|
|
*
|
|
* On each writeback attempt, @wbc tries to detect the majority writer
|
|
* using Boyer-Moore majority vote algorithm. In addition to the byte
|
|
* count from the majority voting, it also counts the bytes written for the
|
|
* current wb and the last round's winner wb (max of last round's current
|
|
* wb, the winner from two rounds ago, and the last round's majority
|
|
* candidate). Keeping track of the historical winner helps the algorithm
|
|
* to semi-reliably detect the most active writer even when it's not the
|
|
* absolute majority.
|
|
*
|
|
* Once the winner of the round is determined, whether the winner is
|
|
* foreign or not and how much IO time the round consumed is recorded in
|
|
* inode->i_wb_frn_history. If the amount of recorded foreign IO time is
|
|
* over a certain threshold, the switch verdict is given.
|
|
*/
|
|
void wbc_detach_inode(struct writeback_control *wbc)
|
|
{
|
|
struct bdi_writeback *wb = wbc->wb;
|
|
struct inode *inode = wbc->inode;
|
|
unsigned long avg_time, max_bytes, max_time;
|
|
u16 history;
|
|
int max_id;
|
|
|
|
if (!wb)
|
|
return;
|
|
|
|
history = inode->i_wb_frn_history;
|
|
avg_time = inode->i_wb_frn_avg_time;
|
|
|
|
/* pick the winner of this round */
|
|
if (wbc->wb_bytes >= wbc->wb_lcand_bytes &&
|
|
wbc->wb_bytes >= wbc->wb_tcand_bytes) {
|
|
max_id = wbc->wb_id;
|
|
max_bytes = wbc->wb_bytes;
|
|
} else if (wbc->wb_lcand_bytes >= wbc->wb_tcand_bytes) {
|
|
max_id = wbc->wb_lcand_id;
|
|
max_bytes = wbc->wb_lcand_bytes;
|
|
} else {
|
|
max_id = wbc->wb_tcand_id;
|
|
max_bytes = wbc->wb_tcand_bytes;
|
|
}
|
|
|
|
/*
|
|
* Calculate the amount of IO time the winner consumed and fold it
|
|
* into the running average kept per inode. If the consumed IO
|
|
* time is lower than avag / WB_FRN_TIME_CUT_DIV, ignore it for
|
|
* deciding whether to switch or not. This is to prevent one-off
|
|
* small dirtiers from skewing the verdict.
|
|
*/
|
|
max_time = DIV_ROUND_UP((max_bytes >> PAGE_SHIFT) << WB_FRN_TIME_SHIFT,
|
|
wb->avg_write_bandwidth);
|
|
if (avg_time)
|
|
avg_time += (max_time >> WB_FRN_TIME_AVG_SHIFT) -
|
|
(avg_time >> WB_FRN_TIME_AVG_SHIFT);
|
|
else
|
|
avg_time = max_time; /* immediate catch up on first run */
|
|
|
|
if (max_time >= avg_time / WB_FRN_TIME_CUT_DIV) {
|
|
int slots;
|
|
|
|
/*
|
|
* The switch verdict is reached if foreign wb's consume
|
|
* more than a certain proportion of IO time in a
|
|
* WB_FRN_TIME_PERIOD. This is loosely tracked by 16 slot
|
|
* history mask where each bit represents one sixteenth of
|
|
* the period. Determine the number of slots to shift into
|
|
* history from @max_time.
|
|
*/
|
|
slots = min(DIV_ROUND_UP(max_time, WB_FRN_HIST_UNIT),
|
|
(unsigned long)WB_FRN_HIST_MAX_SLOTS);
|
|
history <<= slots;
|
|
if (wbc->wb_id != max_id)
|
|
history |= (1U << slots) - 1;
|
|
|
|
/*
|
|
* Switch if the current wb isn't the consistent winner.
|
|
* If there are multiple closely competing dirtiers, the
|
|
* inode may switch across them repeatedly over time, which
|
|
* is okay. The main goal is avoiding keeping an inode on
|
|
* the wrong wb for an extended period of time.
|
|
*/
|
|
if (hweight32(history) > WB_FRN_HIST_THR_SLOTS)
|
|
inode_switch_wbs(inode, max_id);
|
|
}
|
|
|
|
/*
|
|
* Multiple instances of this function may race to update the
|
|
* following fields but we don't mind occassional inaccuracies.
|
|
*/
|
|
inode->i_wb_frn_winner = max_id;
|
|
inode->i_wb_frn_avg_time = min(avg_time, (unsigned long)U16_MAX);
|
|
inode->i_wb_frn_history = history;
|
|
|
|
wb_put(wbc->wb);
|
|
wbc->wb = NULL;
|
|
}
|
|
|
|
/**
|
|
* wbc_account_io - account IO issued during writeback
|
|
* @wbc: writeback_control of the writeback in progress
|
|
* @page: page being written out
|
|
* @bytes: number of bytes being written out
|
|
*
|
|
* @bytes from @page are about to written out during the writeback
|
|
* controlled by @wbc. Keep the book for foreign inode detection. See
|
|
* wbc_detach_inode().
|
|
*/
|
|
void wbc_account_io(struct writeback_control *wbc, struct page *page,
|
|
size_t bytes)
|
|
{
|
|
int id;
|
|
|
|
/*
|
|
* pageout() path doesn't attach @wbc to the inode being written
|
|
* out. This is intentional as we don't want the function to block
|
|
* behind a slow cgroup. Ultimately, we want pageout() to kick off
|
|
* regular writeback instead of writing things out itself.
|
|
*/
|
|
if (!wbc->wb)
|
|
return;
|
|
|
|
id = mem_cgroup_css_from_page(page)->id;
|
|
|
|
if (id == wbc->wb_id) {
|
|
wbc->wb_bytes += bytes;
|
|
return;
|
|
}
|
|
|
|
if (id == wbc->wb_lcand_id)
|
|
wbc->wb_lcand_bytes += bytes;
|
|
|
|
/* Boyer-Moore majority vote algorithm */
|
|
if (!wbc->wb_tcand_bytes)
|
|
wbc->wb_tcand_id = id;
|
|
if (id == wbc->wb_tcand_id)
|
|
wbc->wb_tcand_bytes += bytes;
|
|
else
|
|
wbc->wb_tcand_bytes -= min(bytes, wbc->wb_tcand_bytes);
|
|
}
|
|
EXPORT_SYMBOL_GPL(wbc_account_io);
|
|
|
|
/**
|
|
* inode_congested - test whether an inode is congested
|
|
* @inode: inode to test for congestion (may be NULL)
|
|
* @cong_bits: mask of WB_[a]sync_congested bits to test
|
|
*
|
|
* Tests whether @inode is congested. @cong_bits is the mask of congestion
|
|
* bits to test and the return value is the mask of set bits.
|
|
*
|
|
* If cgroup writeback is enabled for @inode, the congestion state is
|
|
* determined by whether the cgwb (cgroup bdi_writeback) for the blkcg
|
|
* associated with @inode is congested; otherwise, the root wb's congestion
|
|
* state is used.
|
|
*
|
|
* @inode is allowed to be NULL as this function is often called on
|
|
* mapping->host which is NULL for the swapper space.
|
|
*/
|
|
int inode_congested(struct inode *inode, int cong_bits)
|
|
{
|
|
/*
|
|
* Once set, ->i_wb never becomes NULL while the inode is alive.
|
|
* Start transaction iff ->i_wb is visible.
|
|
*/
|
|
if (inode && inode_to_wb_is_valid(inode)) {
|
|
struct bdi_writeback *wb;
|
|
struct wb_lock_cookie lock_cookie = {};
|
|
bool congested;
|
|
|
|
wb = unlocked_inode_to_wb_begin(inode, &lock_cookie);
|
|
congested = wb_congested(wb, cong_bits);
|
|
unlocked_inode_to_wb_end(inode, &lock_cookie);
|
|
return congested;
|
|
}
|
|
|
|
return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);
|
|
}
|
|
EXPORT_SYMBOL_GPL(inode_congested);
|
|
|
|
/**
|
|
* wb_split_bdi_pages - split nr_pages to write according to bandwidth
|
|
* @wb: target bdi_writeback to split @nr_pages to
|
|
* @nr_pages: number of pages to write for the whole bdi
|
|
*
|
|
* Split @wb's portion of @nr_pages according to @wb's write bandwidth in
|
|
* relation to the total write bandwidth of all wb's w/ dirty inodes on
|
|
* @wb->bdi.
|
|
*/
|
|
static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages)
|
|
{
|
|
unsigned long this_bw = wb->avg_write_bandwidth;
|
|
unsigned long tot_bw = atomic_long_read(&wb->bdi->tot_write_bandwidth);
|
|
|
|
if (nr_pages == LONG_MAX)
|
|
return LONG_MAX;
|
|
|
|
/*
|
|
* This may be called on clean wb's and proportional distribution
|
|
* may not make sense, just use the original @nr_pages in those
|
|
* cases. In general, we wanna err on the side of writing more.
|
|
*/
|
|
if (!tot_bw || this_bw >= tot_bw)
|
|
return nr_pages;
|
|
else
|
|
return DIV_ROUND_UP_ULL((u64)nr_pages * this_bw, tot_bw);
|
|
}
|
|
|
|
/**
|
|
* bdi_split_work_to_wbs - split a wb_writeback_work to all wb's of a bdi
|
|
* @bdi: target backing_dev_info
|
|
* @base_work: wb_writeback_work to issue
|
|
* @skip_if_busy: skip wb's which already have writeback in progress
|
|
*
|
|
* Split and issue @base_work to all wb's (bdi_writeback's) of @bdi which
|
|
* have dirty inodes. If @base_work->nr_page isn't %LONG_MAX, it's
|
|
* distributed to the busy wbs according to each wb's proportion in the
|
|
* total active write bandwidth of @bdi.
|
|
*/
|
|
static void bdi_split_work_to_wbs(struct backing_dev_info *bdi,
|
|
struct wb_writeback_work *base_work,
|
|
bool skip_if_busy)
|
|
{
|
|
struct bdi_writeback *last_wb = NULL;
|
|
struct bdi_writeback *wb = list_entry(&bdi->wb_list,
|
|
struct bdi_writeback, bdi_node);
|
|
|
|
might_sleep();
|
|
restart:
|
|
rcu_read_lock();
|
|
list_for_each_entry_continue_rcu(wb, &bdi->wb_list, bdi_node) {
|
|
DEFINE_WB_COMPLETION_ONSTACK(fallback_work_done);
|
|
struct wb_writeback_work fallback_work;
|
|
struct wb_writeback_work *work;
|
|
long nr_pages;
|
|
|
|
if (last_wb) {
|
|
wb_put(last_wb);
|
|
last_wb = NULL;
|
|
}
|
|
|
|
/* SYNC_ALL writes out I_DIRTY_TIME too */
|
|
if (!wb_has_dirty_io(wb) &&
|
|
(base_work->sync_mode == WB_SYNC_NONE ||
|
|
list_empty(&wb->b_dirty_time)))
|
|
continue;
|
|
if (skip_if_busy && writeback_in_progress(wb))
|
|
continue;
|
|
|
|
nr_pages = wb_split_bdi_pages(wb, base_work->nr_pages);
|
|
|
|
work = kmalloc(sizeof(*work), GFP_ATOMIC);
|
|
if (work) {
|
|
*work = *base_work;
|
|
work->nr_pages = nr_pages;
|
|
work->auto_free = 1;
|
|
wb_queue_work(wb, work);
|
|
continue;
|
|
}
|
|
|
|
/* alloc failed, execute synchronously using on-stack fallback */
|
|
work = &fallback_work;
|
|
*work = *base_work;
|
|
work->nr_pages = nr_pages;
|
|
work->auto_free = 0;
|
|
work->done = &fallback_work_done;
|
|
|
|
wb_queue_work(wb, work);
|
|
|
|
/*
|
|
* Pin @wb so that it stays on @bdi->wb_list. This allows
|
|
* continuing iteration from @wb after dropping and
|
|
* regrabbing rcu read lock.
|
|
*/
|
|
wb_get(wb);
|
|
last_wb = wb;
|
|
|
|
rcu_read_unlock();
|
|
wb_wait_for_completion(bdi, &fallback_work_done);
|
|
goto restart;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
if (last_wb)
|
|
wb_put(last_wb);
|
|
}
|
|
|
|
/**
|
|
* cgroup_writeback_umount - flush inode wb switches for umount
|
|
*
|
|
* This function is called when a super_block is about to be destroyed and
|
|
* flushes in-flight inode wb switches. An inode wb switch goes through
|
|
* RCU and then workqueue, so the two need to be flushed in order to ensure
|
|
* that all previously scheduled switches are finished. As wb switches are
|
|
* rare occurrences and synchronize_rcu() can take a while, perform
|
|
* flushing iff wb switches are in flight.
|
|
*/
|
|
void cgroup_writeback_umount(void)
|
|
{
|
|
if (atomic_read(&isw_nr_in_flight)) {
|
|
synchronize_rcu();
|
|
flush_workqueue(isw_wq);
|
|
}
|
|
}
|
|
|
|
static int __init cgroup_writeback_init(void)
|
|
{
|
|
isw_wq = alloc_workqueue("inode_switch_wbs", 0, 0);
|
|
if (!isw_wq)
|
|
return -ENOMEM;
|
|
return 0;
|
|
}
|
|
fs_initcall(cgroup_writeback_init);
|
|
|
|
#else /* CONFIG_CGROUP_WRITEBACK */
|
|
|
|
static struct bdi_writeback *
|
|
locked_inode_to_wb_and_lock_list(struct inode *inode)
|
|
__releases(&inode->i_lock)
|
|
__acquires(&wb->list_lock)
|
|
{
|
|
struct bdi_writeback *wb = inode_to_wb(inode);
|
|
|
|
spin_unlock(&inode->i_lock);
|
|
spin_lock(&wb->list_lock);
|
|
return wb;
|
|
}
|
|
|
|
static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode)
|
|
__acquires(&wb->list_lock)
|
|
{
|
|
struct bdi_writeback *wb = inode_to_wb(inode);
|
|
|
|
spin_lock(&wb->list_lock);
|
|
return wb;
|
|
}
|
|
|
|
static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages)
|
|
{
|
|
return nr_pages;
|
|
}
|
|
|
|
static void bdi_split_work_to_wbs(struct backing_dev_info *bdi,
|
|
struct wb_writeback_work *base_work,
|
|
bool skip_if_busy)
|
|
{
|
|
might_sleep();
|
|
|
|
if (!skip_if_busy || !writeback_in_progress(&bdi->wb)) {
|
|
base_work->auto_free = 0;
|
|
wb_queue_work(&bdi->wb, base_work);
|
|
}
|
|
}
|
|
|
|
#endif /* CONFIG_CGROUP_WRITEBACK */
|
|
|
|
/*
|
|
* Add in the number of potentially dirty inodes, because each inode
|
|
* write can dirty pagecache in the underlying blockdev.
|
|
*/
|
|
static unsigned long get_nr_dirty_pages(void)
|
|
{
|
|
return global_node_page_state(NR_FILE_DIRTY) +
|
|
global_node_page_state(NR_UNSTABLE_NFS) +
|
|
get_nr_dirty_inodes();
|
|
}
|
|
|
|
static void wb_start_writeback(struct bdi_writeback *wb, enum wb_reason reason)
|
|
{
|
|
if (!wb_has_dirty_io(wb))
|
|
return;
|
|
|
|
/*
|
|
* All callers of this function want to start writeback of all
|
|
* dirty pages. Places like vmscan can call this at a very
|
|
* high frequency, causing pointless allocations of tons of
|
|
* work items and keeping the flusher threads busy retrieving
|
|
* that work. Ensure that we only allow one of them pending and
|
|
* inflight at the time.
|
|
*/
|
|
if (test_bit(WB_start_all, &wb->state) ||
|
|
test_and_set_bit(WB_start_all, &wb->state))
|
|
return;
|
|
|
|
wb->start_all_reason = reason;
|
|
wb_wakeup(wb);
|
|
}
|
|
|
|
/**
|
|
* wb_start_background_writeback - start background writeback
|
|
* @wb: bdi_writback to write from
|
|
*
|
|
* Description:
|
|
* This makes sure WB_SYNC_NONE background writeback happens. When
|
|
* this function returns, it is only guaranteed that for given wb
|
|
* some IO is happening if we are over background dirty threshold.
|
|
* Caller need not hold sb s_umount semaphore.
|
|
*/
|
|
void wb_start_background_writeback(struct bdi_writeback *wb)
|
|
{
|
|
/*
|
|
* We just wake up the flusher thread. It will perform background
|
|
* writeback as soon as there is no other work to do.
|
|
*/
|
|
trace_writeback_wake_background(wb);
|
|
wb_wakeup(wb);
|
|
}
|
|
|
|
/*
|
|
* Remove the inode from the writeback list it is on.
|
|
*/
|
|
void inode_io_list_del(struct inode *inode)
|
|
{
|
|
struct bdi_writeback *wb;
|
|
|
|
wb = inode_to_wb_and_lock_list(inode);
|
|
inode_io_list_del_locked(inode, wb);
|
|
spin_unlock(&wb->list_lock);
|
|
}
|
|
|
|
/*
|
|
* mark an inode as under writeback on the sb
|
|
*/
|
|
void sb_mark_inode_writeback(struct inode *inode)
|
|
{
|
|
struct super_block *sb = inode->i_sb;
|
|
unsigned long flags;
|
|
|
|
if (list_empty(&inode->i_wb_list)) {
|
|
spin_lock_irqsave(&sb->s_inode_wblist_lock, flags);
|
|
if (list_empty(&inode->i_wb_list)) {
|
|
list_add_tail(&inode->i_wb_list, &sb->s_inodes_wb);
|
|
trace_sb_mark_inode_writeback(inode);
|
|
}
|
|
spin_unlock_irqrestore(&sb->s_inode_wblist_lock, flags);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* clear an inode as under writeback on the sb
|
|
*/
|
|
void sb_clear_inode_writeback(struct inode *inode)
|
|
{
|
|
struct super_block *sb = inode->i_sb;
|
|
unsigned long flags;
|
|
|
|
if (!list_empty(&inode->i_wb_list)) {
|
|
spin_lock_irqsave(&sb->s_inode_wblist_lock, flags);
|
|
if (!list_empty(&inode->i_wb_list)) {
|
|
list_del_init(&inode->i_wb_list);
|
|
trace_sb_clear_inode_writeback(inode);
|
|
}
|
|
spin_unlock_irqrestore(&sb->s_inode_wblist_lock, flags);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Redirty an inode: set its when-it-was dirtied timestamp and move it to the
|
|
* furthest end of its superblock's dirty-inode list.
|
|
*
|
|
* Before stamping the inode's ->dirtied_when, we check to see whether it is
|
|
* already the most-recently-dirtied inode on the b_dirty list. If that is
|
|
* the case then the inode must have been redirtied while it was being written
|
|
* out and we don't reset its dirtied_when.
|
|
*/
|
|
static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
|
|
{
|
|
if (!list_empty(&wb->b_dirty)) {
|
|
struct inode *tail;
|
|
|
|
tail = wb_inode(wb->b_dirty.next);
|
|
if (time_before(inode->dirtied_when, tail->dirtied_when))
|
|
inode->dirtied_when = jiffies;
|
|
}
|
|
inode_io_list_move_locked(inode, wb, &wb->b_dirty);
|
|
}
|
|
|
|
/*
|
|
* requeue inode for re-scanning after bdi->b_io list is exhausted.
|
|
*/
|
|
static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
|
|
{
|
|
inode_io_list_move_locked(inode, wb, &wb->b_more_io);
|
|
}
|
|
|
|
static void inode_sync_complete(struct inode *inode)
|
|
{
|
|
inode->i_state &= ~I_SYNC;
|
|
/* If inode is clean an unused, put it into LRU now... */
|
|
inode_add_lru(inode);
|
|
/* Waiters must see I_SYNC cleared before being woken up */
|
|
smp_mb();
|
|
wake_up_bit(&inode->i_state, __I_SYNC);
|
|
}
|
|
|
|
static bool inode_dirtied_after(struct inode *inode, unsigned long t)
|
|
{
|
|
bool ret = time_after(inode->dirtied_when, t);
|
|
#ifndef CONFIG_64BIT
|
|
/*
|
|
* For inodes being constantly redirtied, dirtied_when can get stuck.
|
|
* It _appears_ to be in the future, but is actually in distant past.
|
|
* This test is necessary to prevent such wrapped-around relative times
|
|
* from permanently stopping the whole bdi writeback.
|
|
*/
|
|
ret = ret && time_before_eq(inode->dirtied_when, jiffies);
|
|
#endif
|
|
return ret;
|
|
}
|
|
|
|
#define EXPIRE_DIRTY_ATIME 0x0001
|
|
|
|
/*
|
|
* Move expired (dirtied before work->older_than_this) dirty inodes from
|
|
* @delaying_queue to @dispatch_queue.
|
|
*/
|
|
static int move_expired_inodes(struct list_head *delaying_queue,
|
|
struct list_head *dispatch_queue,
|
|
int flags,
|
|
struct wb_writeback_work *work)
|
|
{
|
|
unsigned long *older_than_this = NULL;
|
|
unsigned long expire_time;
|
|
LIST_HEAD(tmp);
|
|
struct list_head *pos, *node;
|
|
struct super_block *sb = NULL;
|
|
struct inode *inode;
|
|
int do_sb_sort = 0;
|
|
int moved = 0;
|
|
|
|
if ((flags & EXPIRE_DIRTY_ATIME) == 0)
|
|
older_than_this = work->older_than_this;
|
|
else if (!work->for_sync) {
|
|
expire_time = jiffies - (dirtytime_expire_interval * HZ);
|
|
older_than_this = &expire_time;
|
|
}
|
|
while (!list_empty(delaying_queue)) {
|
|
inode = wb_inode(delaying_queue->prev);
|
|
if (older_than_this &&
|
|
inode_dirtied_after(inode, *older_than_this))
|
|
break;
|
|
list_move(&inode->i_io_list, &tmp);
|
|
moved++;
|
|
if (flags & EXPIRE_DIRTY_ATIME)
|
|
set_bit(__I_DIRTY_TIME_EXPIRED, &inode->i_state);
|
|
if (sb_is_blkdev_sb(inode->i_sb))
|
|
continue;
|
|
if (sb && sb != inode->i_sb)
|
|
do_sb_sort = 1;
|
|
sb = inode->i_sb;
|
|
}
|
|
|
|
/* just one sb in list, splice to dispatch_queue and we're done */
|
|
if (!do_sb_sort) {
|
|
list_splice(&tmp, dispatch_queue);
|
|
goto out;
|
|
}
|
|
|
|
/* Move inodes from one superblock together */
|
|
while (!list_empty(&tmp)) {
|
|
sb = wb_inode(tmp.prev)->i_sb;
|
|
list_for_each_prev_safe(pos, node, &tmp) {
|
|
inode = wb_inode(pos);
|
|
if (inode->i_sb == sb)
|
|
list_move(&inode->i_io_list, dispatch_queue);
|
|
}
|
|
}
|
|
out:
|
|
return moved;
|
|
}
|
|
|
|
/*
|
|
* Queue all expired dirty inodes for io, eldest first.
|
|
* Before
|
|
* newly dirtied b_dirty b_io b_more_io
|
|
* =============> gf edc BA
|
|
* After
|
|
* newly dirtied b_dirty b_io b_more_io
|
|
* =============> g fBAedc
|
|
* |
|
|
* +--> dequeue for IO
|
|
*/
|
|
static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
|
|
{
|
|
int moved;
|
|
|
|
assert_spin_locked(&wb->list_lock);
|
|
list_splice_init(&wb->b_more_io, &wb->b_io);
|
|
moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, 0, work);
|
|
moved += move_expired_inodes(&wb->b_dirty_time, &wb->b_io,
|
|
EXPIRE_DIRTY_ATIME, work);
|
|
if (moved)
|
|
wb_io_lists_populated(wb);
|
|
trace_writeback_queue_io(wb, work, moved);
|
|
}
|
|
|
|
static int write_inode(struct inode *inode, struct writeback_control *wbc)
|
|
{
|
|
int ret;
|
|
|
|
if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) {
|
|
trace_writeback_write_inode_start(inode, wbc);
|
|
ret = inode->i_sb->s_op->write_inode(inode, wbc);
|
|
trace_writeback_write_inode(inode, wbc);
|
|
return ret;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Wait for writeback on an inode to complete. Called with i_lock held.
|
|
* Caller must make sure inode cannot go away when we drop i_lock.
|
|
*/
|
|
static void __inode_wait_for_writeback(struct inode *inode)
|
|
__releases(inode->i_lock)
|
|
__acquires(inode->i_lock)
|
|
{
|
|
DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
|
|
wait_queue_head_t *wqh;
|
|
|
|
wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
|
|
while (inode->i_state & I_SYNC) {
|
|
spin_unlock(&inode->i_lock);
|
|
__wait_on_bit(wqh, &wq, bit_wait,
|
|
TASK_UNINTERRUPTIBLE);
|
|
spin_lock(&inode->i_lock);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Wait for writeback on an inode to complete. Caller must have inode pinned.
|
|
*/
|
|
void inode_wait_for_writeback(struct inode *inode)
|
|
{
|
|
spin_lock(&inode->i_lock);
|
|
__inode_wait_for_writeback(inode);
|
|
spin_unlock(&inode->i_lock);
|
|
}
|
|
|
|
/*
|
|
* Sleep until I_SYNC is cleared. This function must be called with i_lock
|
|
* held and drops it. It is aimed for callers not holding any inode reference
|
|
* so once i_lock is dropped, inode can go away.
|
|
*/
|
|
static void inode_sleep_on_writeback(struct inode *inode)
|
|
__releases(inode->i_lock)
|
|
{
|
|
DEFINE_WAIT(wait);
|
|
wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
|
|
int sleep;
|
|
|
|
prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
|
|
sleep = inode->i_state & I_SYNC;
|
|
spin_unlock(&inode->i_lock);
|
|
if (sleep)
|
|
schedule();
|
|
finish_wait(wqh, &wait);
|
|
}
|
|
|
|
/*
|
|
* Find proper writeback list for the inode depending on its current state and
|
|
* possibly also change of its state while we were doing writeback. Here we
|
|
* handle things such as livelock prevention or fairness of writeback among
|
|
* inodes. This function can be called only by flusher thread - noone else
|
|
* processes all inodes in writeback lists and requeueing inodes behind flusher
|
|
* thread's back can have unexpected consequences.
|
|
*/
|
|
static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
|
|
struct writeback_control *wbc)
|
|
{
|
|
if (inode->i_state & I_FREEING)
|
|
return;
|
|
|
|
/*
|
|
* Sync livelock prevention. Each inode is tagged and synced in one
|
|
* shot. If still dirty, it will be redirty_tail()'ed below. Update
|
|
* the dirty time to prevent enqueue and sync it again.
|
|
*/
|
|
if ((inode->i_state & I_DIRTY) &&
|
|
(wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
|
|
inode->dirtied_when = jiffies;
|
|
|
|
if (wbc->pages_skipped) {
|
|
/*
|
|
* writeback is not making progress due to locked
|
|
* buffers. Skip this inode for now.
|
|
*/
|
|
redirty_tail(inode, wb);
|
|
return;
|
|
}
|
|
|
|
if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
|
|
/*
|
|
* We didn't write back all the pages. nfs_writepages()
|
|
* sometimes bales out without doing anything.
|
|
*/
|
|
if (wbc->nr_to_write <= 0) {
|
|
/* Slice used up. Queue for next turn. */
|
|
requeue_io(inode, wb);
|
|
} else {
|
|
/*
|
|
* Writeback blocked by something other than
|
|
* congestion. Delay the inode for some time to
|
|
* avoid spinning on the CPU (100% iowait)
|
|
* retrying writeback of the dirty page/inode
|
|
* that cannot be performed immediately.
|
|
*/
|
|
redirty_tail(inode, wb);
|
|
}
|
|
} else if (inode->i_state & I_DIRTY) {
|
|
/*
|
|
* Filesystems can dirty the inode during writeback operations,
|
|
* such as delayed allocation during submission or metadata
|
|
* updates after data IO completion.
|
|
*/
|
|
redirty_tail(inode, wb);
|
|
} else if (inode->i_state & I_DIRTY_TIME) {
|
|
inode->dirtied_when = jiffies;
|
|
inode_io_list_move_locked(inode, wb, &wb->b_dirty_time);
|
|
} else {
|
|
/* The inode is clean. Remove from writeback lists. */
|
|
inode_io_list_del_locked(inode, wb);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Write out an inode and its dirty pages. Do not update the writeback list
|
|
* linkage. That is left to the caller. The caller is also responsible for
|
|
* setting I_SYNC flag and calling inode_sync_complete() to clear it.
|
|
*/
|
|
static int
|
|
__writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
|
|
{
|
|
struct address_space *mapping = inode->i_mapping;
|
|
long nr_to_write = wbc->nr_to_write;
|
|
unsigned dirty;
|
|
int ret;
|
|
|
|
WARN_ON(!(inode->i_state & I_SYNC));
|
|
|
|
trace_writeback_single_inode_start(inode, wbc, nr_to_write);
|
|
|
|
ret = do_writepages(mapping, wbc);
|
|
|
|
/*
|
|
* Make sure to wait on the data before writing out the metadata.
|
|
* This is important for filesystems that modify metadata on data
|
|
* I/O completion. We don't do it for sync(2) writeback because it has a
|
|
* separate, external IO completion path and ->sync_fs for guaranteeing
|
|
* inode metadata is written back correctly.
|
|
*/
|
|
if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync) {
|
|
int err = filemap_fdatawait(mapping);
|
|
if (ret == 0)
|
|
ret = err;
|
|
}
|
|
|
|
/*
|
|
* Some filesystems may redirty the inode during the writeback
|
|
* due to delalloc, clear dirty metadata flags right before
|
|
* write_inode()
|
|
*/
|
|
spin_lock(&inode->i_lock);
|
|
|
|
dirty = inode->i_state & I_DIRTY;
|
|
if (inode->i_state & I_DIRTY_TIME) {
|
|
if ((dirty & I_DIRTY_INODE) ||
|
|
wbc->sync_mode == WB_SYNC_ALL ||
|
|
unlikely(inode->i_state & I_DIRTY_TIME_EXPIRED) ||
|
|
unlikely(time_after(jiffies,
|
|
(inode->dirtied_time_when +
|
|
dirtytime_expire_interval * HZ)))) {
|
|
dirty |= I_DIRTY_TIME | I_DIRTY_TIME_EXPIRED;
|
|
trace_writeback_lazytime(inode);
|
|
}
|
|
} else
|
|
inode->i_state &= ~I_DIRTY_TIME_EXPIRED;
|
|
inode->i_state &= ~dirty;
|
|
|
|
/*
|
|
* Paired with smp_mb() in __mark_inode_dirty(). This allows
|
|
* __mark_inode_dirty() to test i_state without grabbing i_lock -
|
|
* either they see the I_DIRTY bits cleared or we see the dirtied
|
|
* inode.
|
|
*
|
|
* I_DIRTY_PAGES is always cleared together above even if @mapping
|
|
* still has dirty pages. The flag is reinstated after smp_mb() if
|
|
* necessary. This guarantees that either __mark_inode_dirty()
|
|
* sees clear I_DIRTY_PAGES or we see PAGECACHE_TAG_DIRTY.
|
|
*/
|
|
smp_mb();
|
|
|
|
if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
|
|
inode->i_state |= I_DIRTY_PAGES;
|
|
|
|
spin_unlock(&inode->i_lock);
|
|
|
|
if (dirty & I_DIRTY_TIME)
|
|
mark_inode_dirty_sync(inode);
|
|
/* Don't write the inode if only I_DIRTY_PAGES was set */
|
|
if (dirty & ~I_DIRTY_PAGES) {
|
|
int err = write_inode(inode, wbc);
|
|
if (ret == 0)
|
|
ret = err;
|
|
}
|
|
trace_writeback_single_inode(inode, wbc, nr_to_write);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Write out an inode's dirty pages. Either the caller has an active reference
|
|
* on the inode or the inode has I_WILL_FREE set.
|
|
*
|
|
* This function is designed to be called for writing back one inode which
|
|
* we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
|
|
* and does more profound writeback list handling in writeback_sb_inodes().
|
|
*/
|
|
static int writeback_single_inode(struct inode *inode,
|
|
struct writeback_control *wbc)
|
|
{
|
|
struct bdi_writeback *wb;
|
|
int ret = 0;
|
|
|
|
spin_lock(&inode->i_lock);
|
|
if (!atomic_read(&inode->i_count))
|
|
WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
|
|
else
|
|
WARN_ON(inode->i_state & I_WILL_FREE);
|
|
|
|
if (inode->i_state & I_SYNC) {
|
|
if (wbc->sync_mode != WB_SYNC_ALL)
|
|
goto out;
|
|
/*
|
|
* It's a data-integrity sync. We must wait. Since callers hold
|
|
* inode reference or inode has I_WILL_FREE set, it cannot go
|
|
* away under us.
|
|
*/
|
|
__inode_wait_for_writeback(inode);
|
|
}
|
|
WARN_ON(inode->i_state & I_SYNC);
|
|
/*
|
|
* Skip inode if it is clean and we have no outstanding writeback in
|
|
* WB_SYNC_ALL mode. We don't want to mess with writeback lists in this
|
|
* function since flusher thread may be doing for example sync in
|
|
* parallel and if we move the inode, it could get skipped. So here we
|
|
* make sure inode is on some writeback list and leave it there unless
|
|
* we have completely cleaned the inode.
|
|
*/
|
|
if (!(inode->i_state & I_DIRTY_ALL) &&
|
|
(wbc->sync_mode != WB_SYNC_ALL ||
|
|
!mapping_tagged(inode->i_mapping, PAGECACHE_TAG_WRITEBACK)))
|
|
goto out;
|
|
inode->i_state |= I_SYNC;
|
|
wbc_attach_and_unlock_inode(wbc, inode);
|
|
|
|
ret = __writeback_single_inode(inode, wbc);
|
|
|
|
wbc_detach_inode(wbc);
|
|
|
|
wb = inode_to_wb_and_lock_list(inode);
|
|
spin_lock(&inode->i_lock);
|
|
/*
|
|
* If inode is clean, remove it from writeback lists. Otherwise don't
|
|
* touch it. See comment above for explanation.
|
|
*/
|
|
if (!(inode->i_state & I_DIRTY_ALL))
|
|
inode_io_list_del_locked(inode, wb);
|
|
spin_unlock(&wb->list_lock);
|
|
inode_sync_complete(inode);
|
|
out:
|
|
spin_unlock(&inode->i_lock);
|
|
return ret;
|
|
}
|
|
|
|
static long writeback_chunk_size(struct bdi_writeback *wb,
|
|
struct wb_writeback_work *work)
|
|
{
|
|
long pages;
|
|
|
|
/*
|
|
* WB_SYNC_ALL mode does livelock avoidance by syncing dirty
|
|
* inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
|
|
* here avoids calling into writeback_inodes_wb() more than once.
|
|
*
|
|
* The intended call sequence for WB_SYNC_ALL writeback is:
|
|
*
|
|
* wb_writeback()
|
|
* writeback_sb_inodes() <== called only once
|
|
* write_cache_pages() <== called once for each inode
|
|
* (quickly) tag currently dirty pages
|
|
* (maybe slowly) sync all tagged pages
|
|
*/
|
|
if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
|
|
pages = LONG_MAX;
|
|
else {
|
|
pages = min(wb->avg_write_bandwidth / 2,
|
|
global_wb_domain.dirty_limit / DIRTY_SCOPE);
|
|
pages = min(pages, work->nr_pages);
|
|
pages = round_down(pages + MIN_WRITEBACK_PAGES,
|
|
MIN_WRITEBACK_PAGES);
|
|
}
|
|
|
|
return pages;
|
|
}
|
|
|
|
/*
|
|
* Write a portion of b_io inodes which belong to @sb.
|
|
*
|
|
* Return the number of pages and/or inodes written.
|
|
*
|
|
* NOTE! This is called with wb->list_lock held, and will
|
|
* unlock and relock that for each inode it ends up doing
|
|
* IO for.
|
|
*/
|
|
static long writeback_sb_inodes(struct super_block *sb,
|
|
struct bdi_writeback *wb,
|
|
struct wb_writeback_work *work)
|
|
{
|
|
struct writeback_control wbc = {
|
|
.sync_mode = work->sync_mode,
|
|
.tagged_writepages = work->tagged_writepages,
|
|
.for_kupdate = work->for_kupdate,
|
|
.for_background = work->for_background,
|
|
.for_sync = work->for_sync,
|
|
.range_cyclic = work->range_cyclic,
|
|
.range_start = 0,
|
|
.range_end = LLONG_MAX,
|
|
};
|
|
unsigned long start_time = jiffies;
|
|
long write_chunk;
|
|
long wrote = 0; /* count both pages and inodes */
|
|
|
|
while (!list_empty(&wb->b_io)) {
|
|
struct inode *inode = wb_inode(wb->b_io.prev);
|
|
struct bdi_writeback *tmp_wb;
|
|
|
|
if (inode->i_sb != sb) {
|
|
if (work->sb) {
|
|
/*
|
|
* We only want to write back data for this
|
|
* superblock, move all inodes not belonging
|
|
* to it back onto the dirty list.
|
|
*/
|
|
redirty_tail(inode, wb);
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* The inode belongs to a different superblock.
|
|
* Bounce back to the caller to unpin this and
|
|
* pin the next superblock.
|
|
*/
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* Don't bother with new inodes or inodes being freed, first
|
|
* kind does not need periodic writeout yet, and for the latter
|
|
* kind writeout is handled by the freer.
|
|
*/
|
|
spin_lock(&inode->i_lock);
|
|
if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
|
|
spin_unlock(&inode->i_lock);
|
|
redirty_tail(inode, wb);
|
|
continue;
|
|
}
|
|
if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
|
|
/*
|
|
* If this inode is locked for writeback and we are not
|
|
* doing writeback-for-data-integrity, move it to
|
|
* b_more_io so that writeback can proceed with the
|
|
* other inodes on s_io.
|
|
*
|
|
* We'll have another go at writing back this inode
|
|
* when we completed a full scan of b_io.
|
|
*/
|
|
spin_unlock(&inode->i_lock);
|
|
requeue_io(inode, wb);
|
|
trace_writeback_sb_inodes_requeue(inode);
|
|
continue;
|
|
}
|
|
spin_unlock(&wb->list_lock);
|
|
|
|
/*
|
|
* We already requeued the inode if it had I_SYNC set and we
|
|
* are doing WB_SYNC_NONE writeback. So this catches only the
|
|
* WB_SYNC_ALL case.
|
|
*/
|
|
if (inode->i_state & I_SYNC) {
|
|
/* Wait for I_SYNC. This function drops i_lock... */
|
|
inode_sleep_on_writeback(inode);
|
|
/* Inode may be gone, start again */
|
|
spin_lock(&wb->list_lock);
|
|
continue;
|
|
}
|
|
inode->i_state |= I_SYNC;
|
|
wbc_attach_and_unlock_inode(&wbc, inode);
|
|
|
|
write_chunk = writeback_chunk_size(wb, work);
|
|
wbc.nr_to_write = write_chunk;
|
|
wbc.pages_skipped = 0;
|
|
|
|
/*
|
|
* We use I_SYNC to pin the inode in memory. While it is set
|
|
* evict_inode() will wait so the inode cannot be freed.
|
|
*/
|
|
__writeback_single_inode(inode, &wbc);
|
|
|
|
wbc_detach_inode(&wbc);
|
|
work->nr_pages -= write_chunk - wbc.nr_to_write;
|
|
wrote += write_chunk - wbc.nr_to_write;
|
|
|
|
if (need_resched()) {
|
|
/*
|
|
* We're trying to balance between building up a nice
|
|
* long list of IOs to improve our merge rate, and
|
|
* getting those IOs out quickly for anyone throttling
|
|
* in balance_dirty_pages(). cond_resched() doesn't
|
|
* unplug, so get our IOs out the door before we
|
|
* give up the CPU.
|
|
*/
|
|
blk_flush_plug(current);
|
|
cond_resched();
|
|
}
|
|
|
|
/*
|
|
* Requeue @inode if still dirty. Be careful as @inode may
|
|
* have been switched to another wb in the meantime.
|
|
*/
|
|
tmp_wb = inode_to_wb_and_lock_list(inode);
|
|
spin_lock(&inode->i_lock);
|
|
if (!(inode->i_state & I_DIRTY_ALL))
|
|
wrote++;
|
|
requeue_inode(inode, tmp_wb, &wbc);
|
|
inode_sync_complete(inode);
|
|
spin_unlock(&inode->i_lock);
|
|
|
|
if (unlikely(tmp_wb != wb)) {
|
|
spin_unlock(&tmp_wb->list_lock);
|
|
spin_lock(&wb->list_lock);
|
|
}
|
|
|
|
/*
|
|
* bail out to wb_writeback() often enough to check
|
|
* background threshold and other termination conditions.
|
|
*/
|
|
if (wrote) {
|
|
if (time_is_before_jiffies(start_time + HZ / 10UL))
|
|
break;
|
|
if (work->nr_pages <= 0)
|
|
break;
|
|
}
|
|
}
|
|
return wrote;
|
|
}
|
|
|
|
static long __writeback_inodes_wb(struct bdi_writeback *wb,
|
|
struct wb_writeback_work *work)
|
|
{
|
|
unsigned long start_time = jiffies;
|
|
long wrote = 0;
|
|
|
|
while (!list_empty(&wb->b_io)) {
|
|
struct inode *inode = wb_inode(wb->b_io.prev);
|
|
struct super_block *sb = inode->i_sb;
|
|
|
|
if (!trylock_super(sb)) {
|
|
/*
|
|
* trylock_super() may fail consistently due to
|
|
* s_umount being grabbed by someone else. Don't use
|
|
* requeue_io() to avoid busy retrying the inode/sb.
|
|
*/
|
|
redirty_tail(inode, wb);
|
|
continue;
|
|
}
|
|
wrote += writeback_sb_inodes(sb, wb, work);
|
|
up_read(&sb->s_umount);
|
|
|
|
/* refer to the same tests at the end of writeback_sb_inodes */
|
|
if (wrote) {
|
|
if (time_is_before_jiffies(start_time + HZ / 10UL))
|
|
break;
|
|
if (work->nr_pages <= 0)
|
|
break;
|
|
}
|
|
}
|
|
/* Leave any unwritten inodes on b_io */
|
|
return wrote;
|
|
}
|
|
|
|
static long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
|
|
enum wb_reason reason)
|
|
{
|
|
struct wb_writeback_work work = {
|
|
.nr_pages = nr_pages,
|
|
.sync_mode = WB_SYNC_NONE,
|
|
.range_cyclic = 1,
|
|
.reason = reason,
|
|
};
|
|
struct blk_plug plug;
|
|
|
|
blk_start_plug(&plug);
|
|
spin_lock(&wb->list_lock);
|
|
if (list_empty(&wb->b_io))
|
|
queue_io(wb, &work);
|
|
__writeback_inodes_wb(wb, &work);
|
|
spin_unlock(&wb->list_lock);
|
|
blk_finish_plug(&plug);
|
|
|
|
return nr_pages - work.nr_pages;
|
|
}
|
|
|
|
/*
|
|
* Explicit flushing or periodic writeback of "old" data.
|
|
*
|
|
* Define "old": the first time one of an inode's pages is dirtied, we mark the
|
|
* dirtying-time in the inode's address_space. So this periodic writeback code
|
|
* just walks the superblock inode list, writing back any inodes which are
|
|
* older than a specific point in time.
|
|
*
|
|
* Try to run once per dirty_writeback_interval. But if a writeback event
|
|
* takes longer than a dirty_writeback_interval interval, then leave a
|
|
* one-second gap.
|
|
*
|
|
* older_than_this takes precedence over nr_to_write. So we'll only write back
|
|
* all dirty pages if they are all attached to "old" mappings.
|
|
*/
|
|
static long wb_writeback(struct bdi_writeback *wb,
|
|
struct wb_writeback_work *work)
|
|
{
|
|
unsigned long wb_start = jiffies;
|
|
long nr_pages = work->nr_pages;
|
|
unsigned long oldest_jif;
|
|
struct inode *inode;
|
|
long progress;
|
|
struct blk_plug plug;
|
|
|
|
oldest_jif = jiffies;
|
|
work->older_than_this = &oldest_jif;
|
|
|
|
blk_start_plug(&plug);
|
|
spin_lock(&wb->list_lock);
|
|
for (;;) {
|
|
/*
|
|
* Stop writeback when nr_pages has been consumed
|
|
*/
|
|
if (work->nr_pages <= 0)
|
|
break;
|
|
|
|
/*
|
|
* Background writeout and kupdate-style writeback may
|
|
* run forever. Stop them if there is other work to do
|
|
* so that e.g. sync can proceed. They'll be restarted
|
|
* after the other works are all done.
|
|
*/
|
|
if ((work->for_background || work->for_kupdate) &&
|
|
!list_empty(&wb->work_list))
|
|
break;
|
|
|
|
/*
|
|
* For background writeout, stop when we are below the
|
|
* background dirty threshold
|
|
*/
|
|
if (work->for_background && !wb_over_bg_thresh(wb))
|
|
break;
|
|
|
|
/*
|
|
* Kupdate and background works are special and we want to
|
|
* include all inodes that need writing. Livelock avoidance is
|
|
* handled by these works yielding to any other work so we are
|
|
* safe.
|
|
*/
|
|
if (work->for_kupdate) {
|
|
oldest_jif = jiffies -
|
|
msecs_to_jiffies(dirty_expire_interval * 10);
|
|
} else if (work->for_background)
|
|
oldest_jif = jiffies;
|
|
|
|
trace_writeback_start(wb, work);
|
|
if (list_empty(&wb->b_io))
|
|
queue_io(wb, work);
|
|
if (work->sb)
|
|
progress = writeback_sb_inodes(work->sb, wb, work);
|
|
else
|
|
progress = __writeback_inodes_wb(wb, work);
|
|
trace_writeback_written(wb, work);
|
|
|
|
wb_update_bandwidth(wb, wb_start);
|
|
|
|
/*
|
|
* Did we write something? Try for more
|
|
*
|
|
* Dirty inodes are moved to b_io for writeback in batches.
|
|
* The completion of the current batch does not necessarily
|
|
* mean the overall work is done. So we keep looping as long
|
|
* as made some progress on cleaning pages or inodes.
|
|
*/
|
|
if (progress)
|
|
continue;
|
|
/*
|
|
* No more inodes for IO, bail
|
|
*/
|
|
if (list_empty(&wb->b_more_io))
|
|
break;
|
|
/*
|
|
* Nothing written. Wait for some inode to
|
|
* become available for writeback. Otherwise
|
|
* we'll just busyloop.
|
|
*/
|
|
trace_writeback_wait(wb, work);
|
|
inode = wb_inode(wb->b_more_io.prev);
|
|
spin_lock(&inode->i_lock);
|
|
spin_unlock(&wb->list_lock);
|
|
/* This function drops i_lock... */
|
|
inode_sleep_on_writeback(inode);
|
|
spin_lock(&wb->list_lock);
|
|
}
|
|
spin_unlock(&wb->list_lock);
|
|
blk_finish_plug(&plug);
|
|
|
|
return nr_pages - work->nr_pages;
|
|
}
|
|
|
|
/*
|
|
* Return the next wb_writeback_work struct that hasn't been processed yet.
|
|
*/
|
|
static struct wb_writeback_work *get_next_work_item(struct bdi_writeback *wb)
|
|
{
|
|
struct wb_writeback_work *work = NULL;
|
|
|
|
spin_lock_bh(&wb->work_lock);
|
|
if (!list_empty(&wb->work_list)) {
|
|
work = list_entry(wb->work_list.next,
|
|
struct wb_writeback_work, list);
|
|
list_del_init(&work->list);
|
|
}
|
|
spin_unlock_bh(&wb->work_lock);
|
|
return work;
|
|
}
|
|
|
|
static long wb_check_background_flush(struct bdi_writeback *wb)
|
|
{
|
|
if (wb_over_bg_thresh(wb)) {
|
|
|
|
struct wb_writeback_work work = {
|
|
.nr_pages = LONG_MAX,
|
|
.sync_mode = WB_SYNC_NONE,
|
|
.for_background = 1,
|
|
.range_cyclic = 1,
|
|
.reason = WB_REASON_BACKGROUND,
|
|
};
|
|
|
|
return wb_writeback(wb, &work);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static long wb_check_old_data_flush(struct bdi_writeback *wb)
|
|
{
|
|
unsigned long expired;
|
|
long nr_pages;
|
|
|
|
/*
|
|
* When set to zero, disable periodic writeback
|
|
*/
|
|
if (!dirty_writeback_interval)
|
|
return 0;
|
|
|
|
expired = wb->last_old_flush +
|
|
msecs_to_jiffies(dirty_writeback_interval * 10);
|
|
if (time_before(jiffies, expired))
|
|
return 0;
|
|
|
|
wb->last_old_flush = jiffies;
|
|
nr_pages = get_nr_dirty_pages();
|
|
|
|
if (nr_pages) {
|
|
struct wb_writeback_work work = {
|
|
.nr_pages = nr_pages,
|
|
.sync_mode = WB_SYNC_NONE,
|
|
.for_kupdate = 1,
|
|
.range_cyclic = 1,
|
|
.reason = WB_REASON_PERIODIC,
|
|
};
|
|
|
|
return wb_writeback(wb, &work);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static long wb_check_start_all(struct bdi_writeback *wb)
|
|
{
|
|
long nr_pages;
|
|
|
|
if (!test_bit(WB_start_all, &wb->state))
|
|
return 0;
|
|
|
|
nr_pages = get_nr_dirty_pages();
|
|
if (nr_pages) {
|
|
struct wb_writeback_work work = {
|
|
.nr_pages = wb_split_bdi_pages(wb, nr_pages),
|
|
.sync_mode = WB_SYNC_NONE,
|
|
.range_cyclic = 1,
|
|
.reason = wb->start_all_reason,
|
|
};
|
|
|
|
nr_pages = wb_writeback(wb, &work);
|
|
}
|
|
|
|
clear_bit(WB_start_all, &wb->state);
|
|
return nr_pages;
|
|
}
|
|
|
|
|
|
/*
|
|
* Retrieve work items and do the writeback they describe
|
|
*/
|
|
static long wb_do_writeback(struct bdi_writeback *wb)
|
|
{
|
|
struct wb_writeback_work *work;
|
|
long wrote = 0;
|
|
|
|
set_bit(WB_writeback_running, &wb->state);
|
|
while ((work = get_next_work_item(wb)) != NULL) {
|
|
trace_writeback_exec(wb, work);
|
|
wrote += wb_writeback(wb, work);
|
|
finish_writeback_work(wb, work);
|
|
}
|
|
|
|
/*
|
|
* Check for a flush-everything request
|
|
*/
|
|
wrote += wb_check_start_all(wb);
|
|
|
|
/*
|
|
* Check for periodic writeback, kupdated() style
|
|
*/
|
|
wrote += wb_check_old_data_flush(wb);
|
|
wrote += wb_check_background_flush(wb);
|
|
clear_bit(WB_writeback_running, &wb->state);
|
|
|
|
return wrote;
|
|
}
|
|
|
|
/*
|
|
* Handle writeback of dirty data for the device backed by this bdi. Also
|
|
* reschedules periodically and does kupdated style flushing.
|
|
*/
|
|
void wb_workfn(struct work_struct *work)
|
|
{
|
|
struct bdi_writeback *wb = container_of(to_delayed_work(work),
|
|
struct bdi_writeback, dwork);
|
|
long pages_written;
|
|
|
|
set_worker_desc("flush-%s", dev_name(wb->bdi->dev));
|
|
current->flags |= PF_SWAPWRITE;
|
|
|
|
if (likely(!current_is_workqueue_rescuer() ||
|
|
!test_bit(WB_registered, &wb->state))) {
|
|
/*
|
|
* The normal path. Keep writing back @wb until its
|
|
* work_list is empty. Note that this path is also taken
|
|
* if @wb is shutting down even when we're running off the
|
|
* rescuer as work_list needs to be drained.
|
|
*/
|
|
do {
|
|
pages_written = wb_do_writeback(wb);
|
|
trace_writeback_pages_written(pages_written);
|
|
} while (!list_empty(&wb->work_list));
|
|
} else {
|
|
/*
|
|
* bdi_wq can't get enough workers and we're running off
|
|
* the emergency worker. Don't hog it. Hopefully, 1024 is
|
|
* enough for efficient IO.
|
|
*/
|
|
pages_written = writeback_inodes_wb(wb, 1024,
|
|
WB_REASON_FORKER_THREAD);
|
|
trace_writeback_pages_written(pages_written);
|
|
}
|
|
|
|
if (!list_empty(&wb->work_list))
|
|
wb_wakeup(wb);
|
|
else if (wb_has_dirty_io(wb) && dirty_writeback_interval)
|
|
wb_wakeup_delayed(wb);
|
|
|
|
current->flags &= ~PF_SWAPWRITE;
|
|
}
|
|
|
|
/*
|
|
* Start writeback of `nr_pages' pages on this bdi. If `nr_pages' is zero,
|
|
* write back the whole world.
|
|
*/
|
|
static void __wakeup_flusher_threads_bdi(struct backing_dev_info *bdi,
|
|
enum wb_reason reason)
|
|
{
|
|
struct bdi_writeback *wb;
|
|
|
|
if (!bdi_has_dirty_io(bdi))
|
|
return;
|
|
|
|
list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node)
|
|
wb_start_writeback(wb, reason);
|
|
}
|
|
|
|
void wakeup_flusher_threads_bdi(struct backing_dev_info *bdi,
|
|
enum wb_reason reason)
|
|
{
|
|
rcu_read_lock();
|
|
__wakeup_flusher_threads_bdi(bdi, reason);
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
/*
|
|
* Wakeup the flusher threads to start writeback of all currently dirty pages
|
|
*/
|
|
void wakeup_flusher_threads(enum wb_reason reason)
|
|
{
|
|
struct backing_dev_info *bdi;
|
|
|
|
/*
|
|
* If we are expecting writeback progress we must submit plugged IO.
|
|
*/
|
|
if (blk_needs_flush_plug(current))
|
|
blk_schedule_flush_plug(current);
|
|
|
|
rcu_read_lock();
|
|
list_for_each_entry_rcu(bdi, &bdi_list, bdi_list)
|
|
__wakeup_flusher_threads_bdi(bdi, reason);
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
/*
|
|
* Wake up bdi's periodically to make sure dirtytime inodes gets
|
|
* written back periodically. We deliberately do *not* check the
|
|
* b_dirtytime list in wb_has_dirty_io(), since this would cause the
|
|
* kernel to be constantly waking up once there are any dirtytime
|
|
* inodes on the system. So instead we define a separate delayed work
|
|
* function which gets called much more rarely. (By default, only
|
|
* once every 12 hours.)
|
|
*
|
|
* If there is any other write activity going on in the file system,
|
|
* this function won't be necessary. But if the only thing that has
|
|
* happened on the file system is a dirtytime inode caused by an atime
|
|
* update, we need this infrastructure below to make sure that inode
|
|
* eventually gets pushed out to disk.
|
|
*/
|
|
static void wakeup_dirtytime_writeback(struct work_struct *w);
|
|
static DECLARE_DELAYED_WORK(dirtytime_work, wakeup_dirtytime_writeback);
|
|
|
|
static void wakeup_dirtytime_writeback(struct work_struct *w)
|
|
{
|
|
struct backing_dev_info *bdi;
|
|
|
|
rcu_read_lock();
|
|
list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
|
|
struct bdi_writeback *wb;
|
|
|
|
list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node)
|
|
if (!list_empty(&wb->b_dirty_time))
|
|
wb_wakeup(wb);
|
|
}
|
|
rcu_read_unlock();
|
|
schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ);
|
|
}
|
|
|
|
static int __init start_dirtytime_writeback(void)
|
|
{
|
|
schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ);
|
|
return 0;
|
|
}
|
|
__initcall(start_dirtytime_writeback);
|
|
|
|
int dirtytime_interval_handler(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp, loff_t *ppos)
|
|
{
|
|
int ret;
|
|
|
|
ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
|
|
if (ret == 0 && write)
|
|
mod_delayed_work(system_wq, &dirtytime_work, 0);
|
|
return ret;
|
|
}
|
|
|
|
static noinline void block_dump___mark_inode_dirty(struct inode *inode)
|
|
{
|
|
if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
|
|
struct dentry *dentry;
|
|
const char *name = "?";
|
|
|
|
dentry = d_find_alias(inode);
|
|
if (dentry) {
|
|
spin_lock(&dentry->d_lock);
|
|
name = (const char *) dentry->d_name.name;
|
|
}
|
|
printk(KERN_DEBUG
|
|
"%s(%d): dirtied inode %lu (%s) on %s\n",
|
|
current->comm, task_pid_nr(current), inode->i_ino,
|
|
name, inode->i_sb->s_id);
|
|
if (dentry) {
|
|
spin_unlock(&dentry->d_lock);
|
|
dput(dentry);
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* __mark_inode_dirty - internal function
|
|
*
|
|
* @inode: inode to mark
|
|
* @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
|
|
*
|
|
* Mark an inode as dirty. Callers should use mark_inode_dirty or
|
|
* mark_inode_dirty_sync.
|
|
*
|
|
* Put the inode on the super block's dirty list.
|
|
*
|
|
* CAREFUL! We mark it dirty unconditionally, but move it onto the
|
|
* dirty list only if it is hashed or if it refers to a blockdev.
|
|
* If it was not hashed, it will never be added to the dirty list
|
|
* even if it is later hashed, as it will have been marked dirty already.
|
|
*
|
|
* In short, make sure you hash any inodes _before_ you start marking
|
|
* them dirty.
|
|
*
|
|
* Note that for blockdevs, inode->dirtied_when represents the dirtying time of
|
|
* the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
|
|
* the kernel-internal blockdev inode represents the dirtying time of the
|
|
* blockdev's pages. This is why for I_DIRTY_PAGES we always use
|
|
* page->mapping->host, so the page-dirtying time is recorded in the internal
|
|
* blockdev inode.
|
|
*/
|
|
void __mark_inode_dirty(struct inode *inode, int flags)
|
|
{
|
|
struct super_block *sb = inode->i_sb;
|
|
int dirtytime;
|
|
|
|
trace_writeback_mark_inode_dirty(inode, flags);
|
|
|
|
/*
|
|
* Don't do this for I_DIRTY_PAGES - that doesn't actually
|
|
* dirty the inode itself
|
|
*/
|
|
if (flags & (I_DIRTY_INODE | I_DIRTY_TIME)) {
|
|
trace_writeback_dirty_inode_start(inode, flags);
|
|
|
|
if (sb->s_op->dirty_inode)
|
|
sb->s_op->dirty_inode(inode, flags);
|
|
|
|
trace_writeback_dirty_inode(inode, flags);
|
|
}
|
|
if (flags & I_DIRTY_INODE)
|
|
flags &= ~I_DIRTY_TIME;
|
|
dirtytime = flags & I_DIRTY_TIME;
|
|
|
|
/*
|
|
* Paired with smp_mb() in __writeback_single_inode() for the
|
|
* following lockless i_state test. See there for details.
|
|
*/
|
|
smp_mb();
|
|
|
|
if (((inode->i_state & flags) == flags) ||
|
|
(dirtytime && (inode->i_state & I_DIRTY_INODE)))
|
|
return;
|
|
|
|
if (unlikely(block_dump))
|
|
block_dump___mark_inode_dirty(inode);
|
|
|
|
spin_lock(&inode->i_lock);
|
|
if (dirtytime && (inode->i_state & I_DIRTY_INODE))
|
|
goto out_unlock_inode;
|
|
if ((inode->i_state & flags) != flags) {
|
|
const int was_dirty = inode->i_state & I_DIRTY;
|
|
|
|
inode_attach_wb(inode, NULL);
|
|
|
|
if (flags & I_DIRTY_INODE)
|
|
inode->i_state &= ~I_DIRTY_TIME;
|
|
inode->i_state |= flags;
|
|
|
|
/*
|
|
* If the inode is being synced, just update its dirty state.
|
|
* The unlocker will place the inode on the appropriate
|
|
* superblock list, based upon its state.
|
|
*/
|
|
if (inode->i_state & I_SYNC)
|
|
goto out_unlock_inode;
|
|
|
|
/*
|
|
* Only add valid (hashed) inodes to the superblock's
|
|
* dirty list. Add blockdev inodes as well.
|
|
*/
|
|
if (!S_ISBLK(inode->i_mode)) {
|
|
if (inode_unhashed(inode))
|
|
goto out_unlock_inode;
|
|
}
|
|
if (inode->i_state & I_FREEING)
|
|
goto out_unlock_inode;
|
|
|
|
/*
|
|
* If the inode was already on b_dirty/b_io/b_more_io, don't
|
|
* reposition it (that would break b_dirty time-ordering).
|
|
*/
|
|
if (!was_dirty) {
|
|
struct bdi_writeback *wb;
|
|
struct list_head *dirty_list;
|
|
bool wakeup_bdi = false;
|
|
|
|
wb = locked_inode_to_wb_and_lock_list(inode);
|
|
|
|
WARN(bdi_cap_writeback_dirty(wb->bdi) &&
|
|
!test_bit(WB_registered, &wb->state),
|
|
"bdi-%s not registered\n", wb->bdi->name);
|
|
|
|
inode->dirtied_when = jiffies;
|
|
if (dirtytime)
|
|
inode->dirtied_time_when = jiffies;
|
|
|
|
if (inode->i_state & I_DIRTY)
|
|
dirty_list = &wb->b_dirty;
|
|
else
|
|
dirty_list = &wb->b_dirty_time;
|
|
|
|
wakeup_bdi = inode_io_list_move_locked(inode, wb,
|
|
dirty_list);
|
|
|
|
spin_unlock(&wb->list_lock);
|
|
trace_writeback_dirty_inode_enqueue(inode);
|
|
|
|
/*
|
|
* If this is the first dirty inode for this bdi,
|
|
* we have to wake-up the corresponding bdi thread
|
|
* to make sure background write-back happens
|
|
* later.
|
|
*/
|
|
if (bdi_cap_writeback_dirty(wb->bdi) && wakeup_bdi)
|
|
wb_wakeup_delayed(wb);
|
|
return;
|
|
}
|
|
}
|
|
out_unlock_inode:
|
|
spin_unlock(&inode->i_lock);
|
|
}
|
|
EXPORT_SYMBOL(__mark_inode_dirty);
|
|
|
|
/*
|
|
* The @s_sync_lock is used to serialise concurrent sync operations
|
|
* to avoid lock contention problems with concurrent wait_sb_inodes() calls.
|
|
* Concurrent callers will block on the s_sync_lock rather than doing contending
|
|
* walks. The queueing maintains sync(2) required behaviour as all the IO that
|
|
* has been issued up to the time this function is enter is guaranteed to be
|
|
* completed by the time we have gained the lock and waited for all IO that is
|
|
* in progress regardless of the order callers are granted the lock.
|
|
*/
|
|
static void wait_sb_inodes(struct super_block *sb)
|
|
{
|
|
LIST_HEAD(sync_list);
|
|
|
|
/*
|
|
* We need to be protected against the filesystem going from
|
|
* r/o to r/w or vice versa.
|
|
*/
|
|
WARN_ON(!rwsem_is_locked(&sb->s_umount));
|
|
|
|
mutex_lock(&sb->s_sync_lock);
|
|
|
|
/*
|
|
* Splice the writeback list onto a temporary list to avoid waiting on
|
|
* inodes that have started writeback after this point.
|
|
*
|
|
* Use rcu_read_lock() to keep the inodes around until we have a
|
|
* reference. s_inode_wblist_lock protects sb->s_inodes_wb as well as
|
|
* the local list because inodes can be dropped from either by writeback
|
|
* completion.
|
|
*/
|
|
rcu_read_lock();
|
|
spin_lock_irq(&sb->s_inode_wblist_lock);
|
|
list_splice_init(&sb->s_inodes_wb, &sync_list);
|
|
|
|
/*
|
|
* Data integrity sync. Must wait for all pages under writeback, because
|
|
* there may have been pages dirtied before our sync call, but which had
|
|
* writeout started before we write it out. In which case, the inode
|
|
* may not be on the dirty list, but we still have to wait for that
|
|
* writeout.
|
|
*/
|
|
while (!list_empty(&sync_list)) {
|
|
struct inode *inode = list_first_entry(&sync_list, struct inode,
|
|
i_wb_list);
|
|
struct address_space *mapping = inode->i_mapping;
|
|
|
|
/*
|
|
* Move each inode back to the wb list before we drop the lock
|
|
* to preserve consistency between i_wb_list and the mapping
|
|
* writeback tag. Writeback completion is responsible to remove
|
|
* the inode from either list once the writeback tag is cleared.
|
|
*/
|
|
list_move_tail(&inode->i_wb_list, &sb->s_inodes_wb);
|
|
|
|
/*
|
|
* The mapping can appear untagged while still on-list since we
|
|
* do not have the mapping lock. Skip it here, wb completion
|
|
* will remove it.
|
|
*/
|
|
if (!mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK))
|
|
continue;
|
|
|
|
spin_unlock_irq(&sb->s_inode_wblist_lock);
|
|
|
|
spin_lock(&inode->i_lock);
|
|
if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
|
|
spin_unlock(&inode->i_lock);
|
|
|
|
spin_lock_irq(&sb->s_inode_wblist_lock);
|
|
continue;
|
|
}
|
|
__iget(inode);
|
|
spin_unlock(&inode->i_lock);
|
|
rcu_read_unlock();
|
|
|
|
/*
|
|
* We keep the error status of individual mapping so that
|
|
* applications can catch the writeback error using fsync(2).
|
|
* See filemap_fdatawait_keep_errors() for details.
|
|
*/
|
|
filemap_fdatawait_keep_errors(mapping);
|
|
|
|
cond_resched();
|
|
|
|
iput(inode);
|
|
|
|
rcu_read_lock();
|
|
spin_lock_irq(&sb->s_inode_wblist_lock);
|
|
}
|
|
spin_unlock_irq(&sb->s_inode_wblist_lock);
|
|
rcu_read_unlock();
|
|
mutex_unlock(&sb->s_sync_lock);
|
|
}
|
|
|
|
static void __writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr,
|
|
enum wb_reason reason, bool skip_if_busy)
|
|
{
|
|
DEFINE_WB_COMPLETION_ONSTACK(done);
|
|
struct wb_writeback_work work = {
|
|
.sb = sb,
|
|
.sync_mode = WB_SYNC_NONE,
|
|
.tagged_writepages = 1,
|
|
.done = &done,
|
|
.nr_pages = nr,
|
|
.reason = reason,
|
|
};
|
|
struct backing_dev_info *bdi = sb->s_bdi;
|
|
|
|
if (!bdi_has_dirty_io(bdi) || bdi == &noop_backing_dev_info)
|
|
return;
|
|
WARN_ON(!rwsem_is_locked(&sb->s_umount));
|
|
|
|
bdi_split_work_to_wbs(sb->s_bdi, &work, skip_if_busy);
|
|
wb_wait_for_completion(bdi, &done);
|
|
}
|
|
|
|
/**
|
|
* writeback_inodes_sb_nr - writeback dirty inodes from given super_block
|
|
* @sb: the superblock
|
|
* @nr: the number of pages to write
|
|
* @reason: reason why some writeback work initiated
|
|
*
|
|
* Start writeback on some inodes on this super_block. No guarantees are made
|
|
* on how many (if any) will be written, and this function does not wait
|
|
* for IO completion of submitted IO.
|
|
*/
|
|
void writeback_inodes_sb_nr(struct super_block *sb,
|
|
unsigned long nr,
|
|
enum wb_reason reason)
|
|
{
|
|
__writeback_inodes_sb_nr(sb, nr, reason, false);
|
|
}
|
|
EXPORT_SYMBOL(writeback_inodes_sb_nr);
|
|
|
|
/**
|
|
* writeback_inodes_sb - writeback dirty inodes from given super_block
|
|
* @sb: the superblock
|
|
* @reason: reason why some writeback work was initiated
|
|
*
|
|
* Start writeback on some inodes on this super_block. No guarantees are made
|
|
* on how many (if any) will be written, and this function does not wait
|
|
* for IO completion of submitted IO.
|
|
*/
|
|
void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
|
|
{
|
|
return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
|
|
}
|
|
EXPORT_SYMBOL(writeback_inodes_sb);
|
|
|
|
/**
|
|
* try_to_writeback_inodes_sb - try to start writeback if none underway
|
|
* @sb: the superblock
|
|
* @reason: reason why some writeback work was initiated
|
|
*
|
|
* Invoke __writeback_inodes_sb_nr if no writeback is currently underway.
|
|
*/
|
|
void try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
|
|
{
|
|
if (!down_read_trylock(&sb->s_umount))
|
|
return;
|
|
|
|
__writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason, true);
|
|
up_read(&sb->s_umount);
|
|
}
|
|
EXPORT_SYMBOL(try_to_writeback_inodes_sb);
|
|
|
|
/**
|
|
* sync_inodes_sb - sync sb inode pages
|
|
* @sb: the superblock
|
|
*
|
|
* This function writes and waits on any dirty inode belonging to this
|
|
* super_block.
|
|
*/
|
|
void sync_inodes_sb(struct super_block *sb)
|
|
{
|
|
DEFINE_WB_COMPLETION_ONSTACK(done);
|
|
struct wb_writeback_work work = {
|
|
.sb = sb,
|
|
.sync_mode = WB_SYNC_ALL,
|
|
.nr_pages = LONG_MAX,
|
|
.range_cyclic = 0,
|
|
.done = &done,
|
|
.reason = WB_REASON_SYNC,
|
|
.for_sync = 1,
|
|
};
|
|
struct backing_dev_info *bdi = sb->s_bdi;
|
|
|
|
/*
|
|
* Can't skip on !bdi_has_dirty() because we should wait for !dirty
|
|
* inodes under writeback and I_DIRTY_TIME inodes ignored by
|
|
* bdi_has_dirty() need to be written out too.
|
|
*/
|
|
if (bdi == &noop_backing_dev_info)
|
|
return;
|
|
WARN_ON(!rwsem_is_locked(&sb->s_umount));
|
|
|
|
bdi_split_work_to_wbs(bdi, &work, false);
|
|
wb_wait_for_completion(bdi, &done);
|
|
|
|
wait_sb_inodes(sb);
|
|
}
|
|
EXPORT_SYMBOL(sync_inodes_sb);
|
|
|
|
/**
|
|
* write_inode_now - write an inode to disk
|
|
* @inode: inode to write to disk
|
|
* @sync: whether the write should be synchronous or not
|
|
*
|
|
* This function commits an inode to disk immediately if it is dirty. This is
|
|
* primarily needed by knfsd.
|
|
*
|
|
* The caller must either have a ref on the inode or must have set I_WILL_FREE.
|
|
*/
|
|
int write_inode_now(struct inode *inode, int sync)
|
|
{
|
|
struct writeback_control wbc = {
|
|
.nr_to_write = LONG_MAX,
|
|
.sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
|
|
.range_start = 0,
|
|
.range_end = LLONG_MAX,
|
|
};
|
|
|
|
if (!mapping_cap_writeback_dirty(inode->i_mapping))
|
|
wbc.nr_to_write = 0;
|
|
|
|
might_sleep();
|
|
return writeback_single_inode(inode, &wbc);
|
|
}
|
|
EXPORT_SYMBOL(write_inode_now);
|
|
|
|
/**
|
|
* sync_inode - write an inode and its pages to disk.
|
|
* @inode: the inode to sync
|
|
* @wbc: controls the writeback mode
|
|
*
|
|
* sync_inode() will write an inode and its pages to disk. It will also
|
|
* correctly update the inode on its superblock's dirty inode lists and will
|
|
* update inode->i_state.
|
|
*
|
|
* The caller must have a ref on the inode.
|
|
*/
|
|
int sync_inode(struct inode *inode, struct writeback_control *wbc)
|
|
{
|
|
return writeback_single_inode(inode, wbc);
|
|
}
|
|
EXPORT_SYMBOL(sync_inode);
|
|
|
|
/**
|
|
* sync_inode_metadata - write an inode to disk
|
|
* @inode: the inode to sync
|
|
* @wait: wait for I/O to complete.
|
|
*
|
|
* Write an inode to disk and adjust its dirty state after completion.
|
|
*
|
|
* Note: only writes the actual inode, no associated data or other metadata.
|
|
*/
|
|
int sync_inode_metadata(struct inode *inode, int wait)
|
|
{
|
|
struct writeback_control wbc = {
|
|
.sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
|
|
.nr_to_write = 0, /* metadata-only */
|
|
};
|
|
|
|
return sync_inode(inode, &wbc);
|
|
}
|
|
EXPORT_SYMBOL(sync_inode_metadata);
|