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![Jan Kara](/assets/img/avatar_default.png)
WB_SYNC_NONE writeback is done in rounds of 1024 pages so that we don't write out some huge inode for too long while starving writeout of other inodes. To avoid livelocks, we record time we started writeback in wbc->wb_start and do not write out inodes which were dirtied after this time. But currently, writeback_inodes_wb() resets wb_start each time it is called thus effectively invalidating this logic and making any WB_SYNC_NONE writeback prone to livelocks. This patch makes sure wb_start is set only once when we start writeback. Signed-off-by: Jan Kara <jack@suse.cz> Reviewed-by: Wu Fengguang <fengguang.wu@intel.com> Cc: Christoph Hellwig <hch@lst.de> Acked-by: Jens Axboe <jaxboe@fusionio.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1162 lines
30 KiB
C
1162 lines
30 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/module.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/kthread.h>
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#include <linux/freezer.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/buffer_head.h>
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#include "internal.h"
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#define inode_to_bdi(inode) ((inode)->i_mapping->backing_dev_info)
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/*
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* We don't actually have pdflush, but this one is exported though /proc...
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*/
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int nr_pdflush_threads;
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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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enum writeback_sync_modes sync_mode;
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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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struct list_head list; /* pending work list */
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struct completion *done; /* set if the caller waits */
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};
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/**
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* writeback_in_progress - determine whether there is writeback in progress
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* @bdi: the device's backing_dev_info structure.
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*
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* Determine whether there is writeback waiting to be handled against a
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* backing device.
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*/
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int writeback_in_progress(struct backing_dev_info *bdi)
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{
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return !list_empty(&bdi->work_list);
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}
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static void bdi_queue_work(struct backing_dev_info *bdi,
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struct wb_writeback_work *work)
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{
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spin_lock(&bdi->wb_lock);
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list_add_tail(&work->list, &bdi->work_list);
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spin_unlock(&bdi->wb_lock);
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/*
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* If the default thread isn't there, make sure we add it. When
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* it gets created and wakes up, we'll run this work.
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*/
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if (unlikely(list_empty_careful(&bdi->wb_list)))
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wake_up_process(default_backing_dev_info.wb.task);
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else {
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struct bdi_writeback *wb = &bdi->wb;
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if (wb->task)
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wake_up_process(wb->task);
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}
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}
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static void
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__bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
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bool range_cyclic, bool for_background)
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{
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struct wb_writeback_work *work;
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/*
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* This is WB_SYNC_NONE writeback, so if allocation fails just
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* wakeup the thread for old dirty data writeback
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*/
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work = kzalloc(sizeof(*work), GFP_ATOMIC);
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if (!work) {
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if (bdi->wb.task)
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wake_up_process(bdi->wb.task);
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return;
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}
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work->sync_mode = WB_SYNC_NONE;
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work->nr_pages = nr_pages;
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work->range_cyclic = range_cyclic;
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work->for_background = for_background;
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bdi_queue_work(bdi, work);
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}
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/**
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* bdi_start_writeback - start writeback
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* @bdi: the backing device to write from
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* @nr_pages: the number of pages to write
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*
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* Description:
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* This does WB_SYNC_NONE opportunistic writeback. The IO is only
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* started when this function returns, we make no guarentees on
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* completion. Caller need not hold sb s_umount semaphore.
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*
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*/
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void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
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{
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__bdi_start_writeback(bdi, nr_pages, true, false);
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}
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/**
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* bdi_start_background_writeback - start background writeback
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* @bdi: the backing device to write from
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*
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* Description:
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* This does WB_SYNC_NONE background writeback. The IO is only
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* started when this function returns, we make no guarentees on
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* completion. Caller need not hold sb s_umount semaphore.
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*/
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void bdi_start_background_writeback(struct backing_dev_info *bdi)
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{
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__bdi_start_writeback(bdi, LONG_MAX, true, true);
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}
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/*
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* Redirty an inode: set its when-it-was dirtied timestamp and move it to the
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* furthest end of its superblock's dirty-inode list.
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*
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* Before stamping the inode's ->dirtied_when, we check to see whether it is
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* already the most-recently-dirtied inode on the b_dirty list. If that is
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* the case then the inode must have been redirtied while it was being written
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* out and we don't reset its dirtied_when.
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*/
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static void redirty_tail(struct inode *inode)
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{
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struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
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if (!list_empty(&wb->b_dirty)) {
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struct inode *tail;
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tail = list_entry(wb->b_dirty.next, struct inode, i_list);
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if (time_before(inode->dirtied_when, tail->dirtied_when))
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inode->dirtied_when = jiffies;
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}
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list_move(&inode->i_list, &wb->b_dirty);
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}
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/*
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* requeue inode for re-scanning after bdi->b_io list is exhausted.
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*/
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static void requeue_io(struct inode *inode)
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{
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struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
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list_move(&inode->i_list, &wb->b_more_io);
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}
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static void inode_sync_complete(struct inode *inode)
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{
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/*
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* Prevent speculative execution through spin_unlock(&inode_lock);
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*/
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smp_mb();
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wake_up_bit(&inode->i_state, __I_SYNC);
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}
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static bool inode_dirtied_after(struct inode *inode, unsigned long t)
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{
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bool ret = time_after(inode->dirtied_when, t);
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#ifndef CONFIG_64BIT
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/*
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* For inodes being constantly redirtied, dirtied_when can get stuck.
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* It _appears_ to be in the future, but is actually in distant past.
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* This test is necessary to prevent such wrapped-around relative times
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* from permanently stopping the whole bdi writeback.
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*/
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ret = ret && time_before_eq(inode->dirtied_when, jiffies);
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#endif
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return ret;
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}
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/*
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* Move expired dirty inodes from @delaying_queue to @dispatch_queue.
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*/
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static void move_expired_inodes(struct list_head *delaying_queue,
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struct list_head *dispatch_queue,
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unsigned long *older_than_this)
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{
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LIST_HEAD(tmp);
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struct list_head *pos, *node;
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struct super_block *sb = NULL;
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struct inode *inode;
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int do_sb_sort = 0;
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while (!list_empty(delaying_queue)) {
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inode = list_entry(delaying_queue->prev, struct inode, i_list);
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if (older_than_this &&
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inode_dirtied_after(inode, *older_than_this))
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break;
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if (sb && sb != inode->i_sb)
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do_sb_sort = 1;
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sb = inode->i_sb;
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list_move(&inode->i_list, &tmp);
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}
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/* just one sb in list, splice to dispatch_queue and we're done */
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if (!do_sb_sort) {
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list_splice(&tmp, dispatch_queue);
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return;
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}
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/* Move inodes from one superblock together */
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while (!list_empty(&tmp)) {
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inode = list_entry(tmp.prev, struct inode, i_list);
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sb = inode->i_sb;
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list_for_each_prev_safe(pos, node, &tmp) {
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inode = list_entry(pos, struct inode, i_list);
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if (inode->i_sb == sb)
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list_move(&inode->i_list, dispatch_queue);
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}
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}
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}
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/*
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* Queue all expired dirty inodes for io, eldest first.
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*/
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static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
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{
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list_splice_init(&wb->b_more_io, wb->b_io.prev);
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move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);
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}
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static int write_inode(struct inode *inode, struct writeback_control *wbc)
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{
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if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
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return inode->i_sb->s_op->write_inode(inode, wbc);
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return 0;
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}
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/*
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* Wait for writeback on an inode to complete.
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*/
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static void inode_wait_for_writeback(struct inode *inode)
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{
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DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
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wait_queue_head_t *wqh;
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wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
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while (inode->i_state & I_SYNC) {
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spin_unlock(&inode_lock);
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__wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
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spin_lock(&inode_lock);
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}
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}
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/*
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* Write out an inode's dirty pages. Called under inode_lock. Either the
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* caller has ref on the inode (either via __iget or via syscall against an fd)
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* or the inode has I_WILL_FREE set (via generic_forget_inode)
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*
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* If `wait' is set, wait on the writeout.
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*
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* The whole writeout design is quite complex and fragile. We want to avoid
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* starvation of particular inodes when others are being redirtied, prevent
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* livelocks, etc.
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*
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* Called under inode_lock.
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*/
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static int
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writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
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{
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struct address_space *mapping = inode->i_mapping;
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unsigned dirty;
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int ret;
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if (!atomic_read(&inode->i_count))
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WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
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else
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WARN_ON(inode->i_state & I_WILL_FREE);
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if (inode->i_state & I_SYNC) {
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/*
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* If this inode is locked for writeback and we are not doing
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* writeback-for-data-integrity, move it to b_more_io so that
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* writeback can proceed with the other inodes on s_io.
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*
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* We'll have another go at writing back this inode when we
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* completed a full scan of b_io.
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*/
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if (wbc->sync_mode != WB_SYNC_ALL) {
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requeue_io(inode);
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return 0;
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}
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/*
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* It's a data-integrity sync. We must wait.
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*/
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inode_wait_for_writeback(inode);
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}
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BUG_ON(inode->i_state & I_SYNC);
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/* Set I_SYNC, reset I_DIRTY_PAGES */
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inode->i_state |= I_SYNC;
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inode->i_state &= ~I_DIRTY_PAGES;
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spin_unlock(&inode_lock);
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ret = do_writepages(mapping, wbc);
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/*
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* Make sure to wait on the data before writing out the metadata.
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* This is important for filesystems that modify metadata on data
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* I/O completion.
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*/
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if (wbc->sync_mode == WB_SYNC_ALL) {
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int err = filemap_fdatawait(mapping);
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if (ret == 0)
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ret = err;
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}
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/*
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* Some filesystems may redirty the inode during the writeback
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* due to delalloc, clear dirty metadata flags right before
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* write_inode()
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*/
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spin_lock(&inode_lock);
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dirty = inode->i_state & I_DIRTY;
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inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
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spin_unlock(&inode_lock);
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/* Don't write the inode if only I_DIRTY_PAGES was set */
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if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
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int err = write_inode(inode, wbc);
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if (ret == 0)
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ret = err;
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}
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spin_lock(&inode_lock);
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inode->i_state &= ~I_SYNC;
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if (!(inode->i_state & (I_FREEING | I_CLEAR))) {
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if ((inode->i_state & I_DIRTY_PAGES) && wbc->for_kupdate) {
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/*
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* More pages get dirtied by a fast dirtier.
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*/
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goto select_queue;
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} else if (inode->i_state & I_DIRTY) {
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/*
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* At least XFS will redirty the inode during the
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* writeback (delalloc) and on io completion (isize).
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*/
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redirty_tail(inode);
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} else if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
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/*
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* We didn't write back all the pages. nfs_writepages()
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* sometimes bales out without doing anything. Redirty
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* the inode; Move it from b_io onto b_more_io/b_dirty.
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*/
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/*
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* akpm: if the caller was the kupdate function we put
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* this inode at the head of b_dirty so it gets first
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* consideration. Otherwise, move it to the tail, for
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* the reasons described there. I'm not really sure
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* how much sense this makes. Presumably I had a good
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* reasons for doing it this way, and I'd rather not
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* muck with it at present.
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*/
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if (wbc->for_kupdate) {
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/*
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* For the kupdate function we move the inode
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* to b_more_io so it will get more writeout as
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* soon as the queue becomes uncongested.
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*/
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inode->i_state |= I_DIRTY_PAGES;
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select_queue:
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if (wbc->nr_to_write <= 0) {
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/*
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* slice used up: queue for next turn
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*/
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requeue_io(inode);
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} else {
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/*
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* somehow blocked: retry later
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*/
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redirty_tail(inode);
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}
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} else {
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/*
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* Otherwise fully redirty the inode so that
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* other inodes on this superblock will get some
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* writeout. Otherwise heavy writing to one
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* file would indefinitely suspend writeout of
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* all the other files.
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*/
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inode->i_state |= I_DIRTY_PAGES;
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redirty_tail(inode);
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}
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} else if (atomic_read(&inode->i_count)) {
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/*
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* The inode is clean, inuse
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*/
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list_move(&inode->i_list, &inode_in_use);
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} else {
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/*
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* The inode is clean, unused
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*/
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list_move(&inode->i_list, &inode_unused);
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}
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}
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inode_sync_complete(inode);
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return ret;
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}
|
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|
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/*
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* For background writeback the caller does not have the sb pinned
|
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* before calling writeback. So make sure that we do pin it, so it doesn't
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* go away while we are writing inodes from it.
|
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*/
|
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static bool pin_sb_for_writeback(struct super_block *sb)
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{
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spin_lock(&sb_lock);
|
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if (list_empty(&sb->s_instances)) {
|
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spin_unlock(&sb_lock);
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return false;
|
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}
|
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|
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sb->s_count++;
|
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spin_unlock(&sb_lock);
|
|
|
|
if (down_read_trylock(&sb->s_umount)) {
|
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if (sb->s_root)
|
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return true;
|
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up_read(&sb->s_umount);
|
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}
|
|
|
|
put_super(sb);
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return false;
|
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}
|
|
|
|
/*
|
|
* Write a portion of b_io inodes which belong to @sb.
|
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*
|
|
* If @only_this_sb is true, then find and write all such
|
|
* inodes. Otherwise write only ones which go sequentially
|
|
* in reverse order.
|
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*
|
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* Return 1, if the caller writeback routine should be
|
|
* interrupted. Otherwise return 0.
|
|
*/
|
|
static int writeback_sb_inodes(struct super_block *sb, struct bdi_writeback *wb,
|
|
struct writeback_control *wbc, bool only_this_sb)
|
|
{
|
|
while (!list_empty(&wb->b_io)) {
|
|
long pages_skipped;
|
|
struct inode *inode = list_entry(wb->b_io.prev,
|
|
struct inode, i_list);
|
|
|
|
if (inode->i_sb != sb) {
|
|
if (only_this_sb) {
|
|
/*
|
|
* We only want to write back data for this
|
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* superblock, move all inodes not belonging
|
|
* to it back onto the dirty list.
|
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*/
|
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redirty_tail(inode);
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continue;
|
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}
|
|
|
|
/*
|
|
* The inode belongs to a different superblock.
|
|
* Bounce back to the caller to unpin this and
|
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* pin the next superblock.
|
|
*/
|
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return 0;
|
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}
|
|
|
|
if (inode->i_state & (I_NEW | I_WILL_FREE)) {
|
|
requeue_io(inode);
|
|
continue;
|
|
}
|
|
/*
|
|
* Was this inode dirtied after sync_sb_inodes was called?
|
|
* This keeps sync from extra jobs and livelock.
|
|
*/
|
|
if (inode_dirtied_after(inode, wbc->wb_start))
|
|
return 1;
|
|
|
|
BUG_ON(inode->i_state & (I_FREEING | I_CLEAR));
|
|
__iget(inode);
|
|
pages_skipped = wbc->pages_skipped;
|
|
writeback_single_inode(inode, wbc);
|
|
if (wbc->pages_skipped != pages_skipped) {
|
|
/*
|
|
* writeback is not making progress due to locked
|
|
* buffers. Skip this inode for now.
|
|
*/
|
|
redirty_tail(inode);
|
|
}
|
|
spin_unlock(&inode_lock);
|
|
iput(inode);
|
|
cond_resched();
|
|
spin_lock(&inode_lock);
|
|
if (wbc->nr_to_write <= 0) {
|
|
wbc->more_io = 1;
|
|
return 1;
|
|
}
|
|
if (!list_empty(&wb->b_more_io))
|
|
wbc->more_io = 1;
|
|
}
|
|
/* b_io is empty */
|
|
return 1;
|
|
}
|
|
|
|
void writeback_inodes_wb(struct bdi_writeback *wb,
|
|
struct writeback_control *wbc)
|
|
{
|
|
int ret = 0;
|
|
|
|
if (!wbc->wb_start)
|
|
wbc->wb_start = jiffies; /* livelock avoidance */
|
|
spin_lock(&inode_lock);
|
|
if (!wbc->for_kupdate || list_empty(&wb->b_io))
|
|
queue_io(wb, wbc->older_than_this);
|
|
|
|
while (!list_empty(&wb->b_io)) {
|
|
struct inode *inode = list_entry(wb->b_io.prev,
|
|
struct inode, i_list);
|
|
struct super_block *sb = inode->i_sb;
|
|
|
|
if (!pin_sb_for_writeback(sb)) {
|
|
requeue_io(inode);
|
|
continue;
|
|
}
|
|
ret = writeback_sb_inodes(sb, wb, wbc, false);
|
|
drop_super(sb);
|
|
|
|
if (ret)
|
|
break;
|
|
}
|
|
spin_unlock(&inode_lock);
|
|
/* Leave any unwritten inodes on b_io */
|
|
}
|
|
|
|
static void __writeback_inodes_sb(struct super_block *sb,
|
|
struct bdi_writeback *wb, struct writeback_control *wbc)
|
|
{
|
|
WARN_ON(!rwsem_is_locked(&sb->s_umount));
|
|
|
|
spin_lock(&inode_lock);
|
|
if (!wbc->for_kupdate || list_empty(&wb->b_io))
|
|
queue_io(wb, wbc->older_than_this);
|
|
writeback_sb_inodes(sb, wb, wbc, true);
|
|
spin_unlock(&inode_lock);
|
|
}
|
|
|
|
/*
|
|
* The maximum number of pages to writeout in a single bdi flush/kupdate
|
|
* operation. We do this so we don't hold I_SYNC against an inode for
|
|
* enormous amounts of time, which would block a userspace task which has
|
|
* been forced to throttle against that inode. Also, the code reevaluates
|
|
* the dirty each time it has written this many pages.
|
|
*/
|
|
#define MAX_WRITEBACK_PAGES 1024
|
|
|
|
static inline bool over_bground_thresh(void)
|
|
{
|
|
unsigned long background_thresh, dirty_thresh;
|
|
|
|
get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL);
|
|
|
|
return (global_page_state(NR_FILE_DIRTY) +
|
|
global_page_state(NR_UNSTABLE_NFS) >= background_thresh);
|
|
}
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
struct writeback_control wbc = {
|
|
.sync_mode = work->sync_mode,
|
|
.older_than_this = NULL,
|
|
.for_kupdate = work->for_kupdate,
|
|
.for_background = work->for_background,
|
|
.range_cyclic = work->range_cyclic,
|
|
};
|
|
unsigned long oldest_jif;
|
|
long wrote = 0;
|
|
struct inode *inode;
|
|
|
|
if (wbc.for_kupdate) {
|
|
wbc.older_than_this = &oldest_jif;
|
|
oldest_jif = jiffies -
|
|
msecs_to_jiffies(dirty_expire_interval * 10);
|
|
}
|
|
if (!wbc.range_cyclic) {
|
|
wbc.range_start = 0;
|
|
wbc.range_end = LLONG_MAX;
|
|
}
|
|
|
|
wbc.wb_start = jiffies; /* livelock avoidance */
|
|
for (;;) {
|
|
/*
|
|
* Stop writeback when nr_pages has been consumed
|
|
*/
|
|
if (work->nr_pages <= 0)
|
|
break;
|
|
|
|
/*
|
|
* For background writeout, stop when we are below the
|
|
* background dirty threshold
|
|
*/
|
|
if (work->for_background && !over_bground_thresh())
|
|
break;
|
|
|
|
wbc.more_io = 0;
|
|
wbc.nr_to_write = MAX_WRITEBACK_PAGES;
|
|
wbc.pages_skipped = 0;
|
|
if (work->sb)
|
|
__writeback_inodes_sb(work->sb, wb, &wbc);
|
|
else
|
|
writeback_inodes_wb(wb, &wbc);
|
|
work->nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
|
|
wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;
|
|
|
|
/*
|
|
* If we consumed everything, see if we have more
|
|
*/
|
|
if (wbc.nr_to_write <= 0)
|
|
continue;
|
|
/*
|
|
* Didn't write everything and we don't have more IO, bail
|
|
*/
|
|
if (!wbc.more_io)
|
|
break;
|
|
/*
|
|
* Did we write something? Try for more
|
|
*/
|
|
if (wbc.nr_to_write < MAX_WRITEBACK_PAGES)
|
|
continue;
|
|
/*
|
|
* Nothing written. Wait for some inode to
|
|
* become available for writeback. Otherwise
|
|
* we'll just busyloop.
|
|
*/
|
|
spin_lock(&inode_lock);
|
|
if (!list_empty(&wb->b_more_io)) {
|
|
inode = list_entry(wb->b_more_io.prev,
|
|
struct inode, i_list);
|
|
inode_wait_for_writeback(inode);
|
|
}
|
|
spin_unlock(&inode_lock);
|
|
}
|
|
|
|
return wrote;
|
|
}
|
|
|
|
/*
|
|
* Return the next wb_writeback_work struct that hasn't been processed yet.
|
|
*/
|
|
static struct wb_writeback_work *
|
|
get_next_work_item(struct backing_dev_info *bdi, struct bdi_writeback *wb)
|
|
{
|
|
struct wb_writeback_work *work = NULL;
|
|
|
|
spin_lock(&bdi->wb_lock);
|
|
if (!list_empty(&bdi->work_list)) {
|
|
work = list_entry(bdi->work_list.next,
|
|
struct wb_writeback_work, list);
|
|
list_del_init(&work->list);
|
|
}
|
|
spin_unlock(&bdi->wb_lock);
|
|
return work;
|
|
}
|
|
|
|
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 = global_page_state(NR_FILE_DIRTY) +
|
|
global_page_state(NR_UNSTABLE_NFS) +
|
|
(inodes_stat.nr_inodes - inodes_stat.nr_unused);
|
|
|
|
if (nr_pages) {
|
|
struct wb_writeback_work work = {
|
|
.nr_pages = nr_pages,
|
|
.sync_mode = WB_SYNC_NONE,
|
|
.for_kupdate = 1,
|
|
.range_cyclic = 1,
|
|
};
|
|
|
|
return wb_writeback(wb, &work);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Retrieve work items and do the writeback they describe
|
|
*/
|
|
long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
|
|
{
|
|
struct backing_dev_info *bdi = wb->bdi;
|
|
struct wb_writeback_work *work;
|
|
long wrote = 0;
|
|
|
|
while ((work = get_next_work_item(bdi, wb)) != NULL) {
|
|
/*
|
|
* Override sync mode, in case we must wait for completion
|
|
* because this thread is exiting now.
|
|
*/
|
|
if (force_wait)
|
|
work->sync_mode = WB_SYNC_ALL;
|
|
|
|
wrote += wb_writeback(wb, work);
|
|
|
|
/*
|
|
* Notify the caller of completion if this is a synchronous
|
|
* work item, otherwise just free it.
|
|
*/
|
|
if (work->done)
|
|
complete(work->done);
|
|
else
|
|
kfree(work);
|
|
}
|
|
|
|
/*
|
|
* Check for periodic writeback, kupdated() style
|
|
*/
|
|
wrote += wb_check_old_data_flush(wb);
|
|
|
|
return wrote;
|
|
}
|
|
|
|
/*
|
|
* Handle writeback of dirty data for the device backed by this bdi. Also
|
|
* wakes up periodically and does kupdated style flushing.
|
|
*/
|
|
int bdi_writeback_task(struct bdi_writeback *wb)
|
|
{
|
|
unsigned long last_active = jiffies;
|
|
unsigned long wait_jiffies = -1UL;
|
|
long pages_written;
|
|
|
|
while (!kthread_should_stop()) {
|
|
pages_written = wb_do_writeback(wb, 0);
|
|
|
|
if (pages_written)
|
|
last_active = jiffies;
|
|
else if (wait_jiffies != -1UL) {
|
|
unsigned long max_idle;
|
|
|
|
/*
|
|
* Longest period of inactivity that we tolerate. If we
|
|
* see dirty data again later, the task will get
|
|
* recreated automatically.
|
|
*/
|
|
max_idle = max(5UL * 60 * HZ, wait_jiffies);
|
|
if (time_after(jiffies, max_idle + last_active))
|
|
break;
|
|
}
|
|
|
|
if (dirty_writeback_interval) {
|
|
wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
|
|
schedule_timeout_interruptible(wait_jiffies);
|
|
} else {
|
|
set_current_state(TASK_INTERRUPTIBLE);
|
|
if (list_empty_careful(&wb->bdi->work_list) &&
|
|
!kthread_should_stop())
|
|
schedule();
|
|
__set_current_state(TASK_RUNNING);
|
|
}
|
|
|
|
try_to_freeze();
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
|
|
* the whole world.
|
|
*/
|
|
void wakeup_flusher_threads(long nr_pages)
|
|
{
|
|
struct backing_dev_info *bdi;
|
|
|
|
if (!nr_pages) {
|
|
nr_pages = global_page_state(NR_FILE_DIRTY) +
|
|
global_page_state(NR_UNSTABLE_NFS);
|
|
}
|
|
|
|
rcu_read_lock();
|
|
list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
|
|
if (!bdi_has_dirty_io(bdi))
|
|
continue;
|
|
__bdi_start_writeback(bdi, nr_pages, false, false);
|
|
}
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
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.
|
|
*
|
|
* This function *must* be atomic for the I_DIRTY_PAGES case -
|
|
* set_page_dirty() is called under spinlock in several places.
|
|
*
|
|
* 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;
|
|
|
|
/*
|
|
* Don't do this for I_DIRTY_PAGES - that doesn't actually
|
|
* dirty the inode itself
|
|
*/
|
|
if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
|
|
if (sb->s_op->dirty_inode)
|
|
sb->s_op->dirty_inode(inode);
|
|
}
|
|
|
|
/*
|
|
* make sure that changes are seen by all cpus before we test i_state
|
|
* -- mikulas
|
|
*/
|
|
smp_mb();
|
|
|
|
/* avoid the locking if we can */
|
|
if ((inode->i_state & flags) == flags)
|
|
return;
|
|
|
|
if (unlikely(block_dump))
|
|
block_dump___mark_inode_dirty(inode);
|
|
|
|
spin_lock(&inode_lock);
|
|
if ((inode->i_state & flags) != flags) {
|
|
const int was_dirty = inode->i_state & I_DIRTY;
|
|
|
|
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;
|
|
|
|
/*
|
|
* Only add valid (hashed) inodes to the superblock's
|
|
* dirty list. Add blockdev inodes as well.
|
|
*/
|
|
if (!S_ISBLK(inode->i_mode)) {
|
|
if (hlist_unhashed(&inode->i_hash))
|
|
goto out;
|
|
}
|
|
if (inode->i_state & (I_FREEING|I_CLEAR))
|
|
goto out;
|
|
|
|
/*
|
|
* 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 = &inode_to_bdi(inode)->wb;
|
|
struct backing_dev_info *bdi = wb->bdi;
|
|
|
|
if (bdi_cap_writeback_dirty(bdi) &&
|
|
!test_bit(BDI_registered, &bdi->state)) {
|
|
WARN_ON(1);
|
|
printk(KERN_ERR "bdi-%s not registered\n",
|
|
bdi->name);
|
|
}
|
|
|
|
inode->dirtied_when = jiffies;
|
|
list_move(&inode->i_list, &wb->b_dirty);
|
|
}
|
|
}
|
|
out:
|
|
spin_unlock(&inode_lock);
|
|
}
|
|
EXPORT_SYMBOL(__mark_inode_dirty);
|
|
|
|
/*
|
|
* Write out a superblock's list of dirty inodes. A wait will be performed
|
|
* upon no inodes, all inodes or the final one, depending upon sync_mode.
|
|
*
|
|
* If older_than_this is non-NULL, then only write out inodes which
|
|
* had their first dirtying at a time earlier than *older_than_this.
|
|
*
|
|
* If `bdi' is non-zero then we're being asked to writeback a specific queue.
|
|
* This function assumes that the blockdev superblock's inodes are backed by
|
|
* a variety of queues, so all inodes are searched. For other superblocks,
|
|
* assume that all inodes are backed by the same queue.
|
|
*
|
|
* The inodes to be written are parked on bdi->b_io. They are moved back onto
|
|
* bdi->b_dirty as they are selected for writing. This way, none can be missed
|
|
* on the writer throttling path, and we get decent balancing between many
|
|
* throttled threads: we don't want them all piling up on inode_sync_wait.
|
|
*/
|
|
static void wait_sb_inodes(struct super_block *sb)
|
|
{
|
|
struct inode *inode, *old_inode = NULL;
|
|
|
|
/*
|
|
* 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));
|
|
|
|
spin_lock(&inode_lock);
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
|
|
struct address_space *mapping;
|
|
|
|
if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE|I_NEW))
|
|
continue;
|
|
mapping = inode->i_mapping;
|
|
if (mapping->nrpages == 0)
|
|
continue;
|
|
__iget(inode);
|
|
spin_unlock(&inode_lock);
|
|
/*
|
|
* We hold a reference to 'inode' so it couldn't have
|
|
* been removed from s_inodes list while we dropped the
|
|
* inode_lock. We cannot iput the inode now as we can
|
|
* be holding the last reference and we cannot iput it
|
|
* under inode_lock. So we keep the reference and iput
|
|
* it later.
|
|
*/
|
|
iput(old_inode);
|
|
old_inode = inode;
|
|
|
|
filemap_fdatawait(mapping);
|
|
|
|
cond_resched();
|
|
|
|
spin_lock(&inode_lock);
|
|
}
|
|
spin_unlock(&inode_lock);
|
|
iput(old_inode);
|
|
}
|
|
|
|
/**
|
|
* writeback_inodes_sb - writeback dirty inodes from given super_block
|
|
* @sb: the superblock
|
|
*
|
|
* 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. The number of pages submitted is
|
|
* returned.
|
|
*/
|
|
void writeback_inodes_sb(struct super_block *sb)
|
|
{
|
|
unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
|
|
unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
|
|
DECLARE_COMPLETION_ONSTACK(done);
|
|
struct wb_writeback_work work = {
|
|
.sb = sb,
|
|
.sync_mode = WB_SYNC_NONE,
|
|
.done = &done,
|
|
};
|
|
|
|
WARN_ON(!rwsem_is_locked(&sb->s_umount));
|
|
|
|
work.nr_pages = nr_dirty + nr_unstable +
|
|
(inodes_stat.nr_inodes - inodes_stat.nr_unused);
|
|
|
|
bdi_queue_work(sb->s_bdi, &work);
|
|
wait_for_completion(&done);
|
|
}
|
|
EXPORT_SYMBOL(writeback_inodes_sb);
|
|
|
|
/**
|
|
* writeback_inodes_sb_if_idle - start writeback if none underway
|
|
* @sb: the superblock
|
|
*
|
|
* Invoke writeback_inodes_sb if no writeback is currently underway.
|
|
* Returns 1 if writeback was started, 0 if not.
|
|
*/
|
|
int writeback_inodes_sb_if_idle(struct super_block *sb)
|
|
{
|
|
if (!writeback_in_progress(sb->s_bdi)) {
|
|
down_read(&sb->s_umount);
|
|
writeback_inodes_sb(sb);
|
|
up_read(&sb->s_umount);
|
|
return 1;
|
|
} else
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
|
|
|
|
/**
|
|
* sync_inodes_sb - sync sb inode pages
|
|
* @sb: the superblock
|
|
*
|
|
* This function writes and waits on any dirty inode belonging to this
|
|
* super_block. The number of pages synced is returned.
|
|
*/
|
|
void sync_inodes_sb(struct super_block *sb)
|
|
{
|
|
DECLARE_COMPLETION_ONSTACK(done);
|
|
struct wb_writeback_work work = {
|
|
.sb = sb,
|
|
.sync_mode = WB_SYNC_ALL,
|
|
.nr_pages = LONG_MAX,
|
|
.range_cyclic = 0,
|
|
.done = &done,
|
|
};
|
|
|
|
WARN_ON(!rwsem_is_locked(&sb->s_umount));
|
|
|
|
bdi_queue_work(sb->s_bdi, &work);
|
|
wait_for_completion(&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)
|
|
{
|
|
int ret;
|
|
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();
|
|
spin_lock(&inode_lock);
|
|
ret = writeback_single_inode(inode, &wbc);
|
|
spin_unlock(&inode_lock);
|
|
if (sync)
|
|
inode_sync_wait(inode);
|
|
return ret;
|
|
}
|
|
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)
|
|
{
|
|
int ret;
|
|
|
|
spin_lock(&inode_lock);
|
|
ret = writeback_single_inode(inode, wbc);
|
|
spin_unlock(&inode_lock);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(sync_inode);
|