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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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![J. Bruce Fields](/assets/img/avatar_default.png)
Setting the task state here may cause us to miss the wake up from kthread_stop(), so we need to recheck kthread_should_stop() or risk sleeping forever in the following schedule(). Symptom was an indefinite hang on an NFSv4 mount. (NFSv4 may create multiple mounts in a temporary namespace while traversing the mount path, and since the temporary namespace is immediately destroyed, it may end up destroying a mount very soon after it was created, possibly making this race more likely.) INFO: task mount.nfs4:4314 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. mount.nfs4 D 0000000000000000 2880 4314 4313 0x00000000 ffff88001ed6da28 0000000000000046 ffff88001ed6dfd8 ffff88001ed6dfd8 ffff88001ed6c000 ffff88001ed6c000 ffff88001ed6c000 ffff88001e5003a0 ffff88001ed6dfd8 ffff88001e5003a8 ffff88001ed6c000 ffff88001ed6dfd8 Call Trace: [<ffffffff8196090d>] schedule_timeout+0x1cd/0x2e0 [<ffffffff8106a31c>] ? mark_held_locks+0x6c/0xa0 [<ffffffff819639a0>] ? _raw_spin_unlock_irq+0x30/0x60 [<ffffffff8106a5fd>] ? trace_hardirqs_on_caller+0x14d/0x190 [<ffffffff819671fe>] ? sub_preempt_count+0xe/0xd0 [<ffffffff8195fc80>] wait_for_common+0x120/0x190 [<ffffffff81033c70>] ? default_wake_function+0x0/0x20 [<ffffffff8195fdcd>] wait_for_completion+0x1d/0x20 [<ffffffff810595fa>] kthread_stop+0x4a/0x150 [<ffffffff81061a60>] ? thaw_process+0x70/0x80 [<ffffffff810cc68a>] bdi_unregister+0x10a/0x1a0 [<ffffffff81229dc9>] nfs_put_super+0x19/0x20 [<ffffffff810ee8c4>] generic_shutdown_super+0x54/0xe0 [<ffffffff810ee9b6>] kill_anon_super+0x16/0x60 [<ffffffff8122d3b9>] nfs4_kill_super+0x39/0x90 [<ffffffff810eda45>] deactivate_locked_super+0x45/0x60 [<ffffffff810edfb9>] deactivate_super+0x49/0x70 [<ffffffff81108294>] mntput_no_expire+0x84/0xe0 [<ffffffff811084ef>] release_mounts+0x9f/0xc0 [<ffffffff81108575>] put_mnt_ns+0x65/0x80 [<ffffffff8122cc56>] nfs_follow_remote_path+0x1e6/0x420 [<ffffffff8122cfbf>] nfs4_try_mount+0x6f/0xd0 [<ffffffff8122d0c2>] nfs4_get_sb+0xa2/0x360 [<ffffffff810edcb8>] vfs_kern_mount+0x88/0x1f0 [<ffffffff810ede92>] do_kern_mount+0x52/0x130 [<ffffffff81963d9a>] ? _lock_kernel+0x6a/0x170 [<ffffffff81108e9e>] do_mount+0x26e/0x7f0 [<ffffffff81106b3a>] ? copy_mount_options+0xea/0x190 [<ffffffff811094b8>] sys_mount+0x98/0xf0 [<ffffffff810024d8>] system_call_fastpath+0x16/0x1b 1 lock held by mount.nfs4/4314: #0: (&type->s_umount_key#24){+.+...}, at: [<ffffffff810edfb1>] deactivate_super+0x41/0x70 Signed-off-by: J. Bruce Fields <bfields@redhat.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com> Acked-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
1192 lines
31 KiB
C
1192 lines
31 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 <linux/tracepoint.h>
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#include "internal.h"
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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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* Include the creation of the trace points after defining the
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* wb_writeback_work structure so that the definition remains local to this
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* 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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#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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* 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 test_bit(BDI_writeback_running, &bdi->state);
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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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trace_writeback_queue(bdi, work);
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spin_lock_bh(&bdi->wb_lock);
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list_add_tail(&work->list, &bdi->work_list);
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if (bdi->wb.task) {
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wake_up_process(bdi->wb.task);
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} else {
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/*
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* The bdi thread isn't there, wake up the forker thread which
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* will create and run it.
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*/
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trace_writeback_nothread(bdi, work);
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wake_up_process(default_backing_dev_info.wb.task);
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}
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spin_unlock_bh(&bdi->wb_lock);
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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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trace_writeback_nowork(bdi);
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wake_up_process(bdi->wb.task);
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}
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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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* Before
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* newly dirtied b_dirty b_io b_more_io
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* =============> gf edc BA
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* After
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* newly dirtied b_dirty b_io b_more_io
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* =============> g fBAedc
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* |
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* +--> dequeue for IO
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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);
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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)) {
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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.
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*/
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inode->i_state |= I_DIRTY_PAGES;
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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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* Writeback blocked by something other than
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* congestion. Delay the inode for some time to
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* avoid spinning on the CPU (100% iowait)
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* retrying writeback of the dirty page/inode
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* that cannot be performed immediately.
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*/
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redirty_tail(inode);
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}
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} else if (inode->i_state & I_DIRTY) {
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/*
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* Filesystems can dirty the inode during writeback
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* operations, such as delayed allocation during
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* submission or metadata updates after data IO
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* completion.
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*/
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redirty_tail(inode);
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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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* 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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sb->s_count++;
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spin_unlock(&sb_lock);
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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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}
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put_super(sb);
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return false;
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}
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/*
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* Write a portion of b_io inodes which belong to @sb.
|
|
*
|
|
* If @only_this_sb is true, then find and write all such
|
|
* inodes. Otherwise write only ones which go sequentially
|
|
* in reverse order.
|
|
*
|
|
* 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
|
|
* superblock, move all inodes not belonging
|
|
* to it back onto the dirty list.
|
|
*/
|
|
redirty_tail(inode);
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* The inode belongs to a different superblock.
|
|
* Bounce back to the caller to unpin this and
|
|
* pin the next superblock.
|
|
*/
|
|
return 0;
|
|
}
|
|
|
|
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);
|
|
__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;
|
|
|
|
global_dirty_limits(&background_thresh, &dirty_thresh);
|
|
|
|
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;
|
|
|
|
trace_wbc_writeback_start(&wbc, wb->bdi);
|
|
if (work->sb)
|
|
__writeback_inodes_sb(work->sb, wb, &wbc);
|
|
else
|
|
writeback_inodes_wb(wb, &wbc);
|
|
trace_wbc_writeback_written(&wbc, wb->bdi);
|
|
|
|
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);
|
|
trace_wbc_writeback_wait(&wbc, wb->bdi);
|
|
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 wb_writeback_work *work = NULL;
|
|
|
|
spin_lock_bh(&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_bh(&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;
|
|
|
|
set_bit(BDI_writeback_running, &wb->bdi->state);
|
|
while ((work = get_next_work_item(bdi)) != 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;
|
|
|
|
trace_writeback_exec(bdi, work);
|
|
|
|
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);
|
|
clear_bit(BDI_writeback_running, &wb->bdi->state);
|
|
|
|
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_thread(void *data)
|
|
{
|
|
struct bdi_writeback *wb = data;
|
|
struct backing_dev_info *bdi = wb->bdi;
|
|
long pages_written;
|
|
|
|
current->flags |= PF_FLUSHER | PF_SWAPWRITE;
|
|
set_freezable();
|
|
wb->last_active = jiffies;
|
|
|
|
/*
|
|
* Our parent may run at a different priority, just set us to normal
|
|
*/
|
|
set_user_nice(current, 0);
|
|
|
|
trace_writeback_thread_start(bdi);
|
|
|
|
while (!kthread_should_stop()) {
|
|
/*
|
|
* Remove own delayed wake-up timer, since we are already awake
|
|
* and we'll take care of the preriodic write-back.
|
|
*/
|
|
del_timer(&wb->wakeup_timer);
|
|
|
|
pages_written = wb_do_writeback(wb, 0);
|
|
|
|
trace_writeback_pages_written(pages_written);
|
|
|
|
if (pages_written)
|
|
wb->last_active = jiffies;
|
|
|
|
set_current_state(TASK_INTERRUPTIBLE);
|
|
if (!list_empty(&bdi->work_list) || kthread_should_stop()) {
|
|
__set_current_state(TASK_RUNNING);
|
|
continue;
|
|
}
|
|
|
|
if (wb_has_dirty_io(wb) && dirty_writeback_interval)
|
|
schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
|
|
else {
|
|
/*
|
|
* We have nothing to do, so can go sleep without any
|
|
* timeout and save power. When a work is queued or
|
|
* something is made dirty - we will be woken up.
|
|
*/
|
|
schedule();
|
|
}
|
|
|
|
try_to_freeze();
|
|
}
|
|
|
|
/* Flush any work that raced with us exiting */
|
|
if (!list_empty(&bdi->work_list))
|
|
wb_do_writeback(wb, 1);
|
|
|
|
trace_writeback_thread_stop(bdi);
|
|
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;
|
|
struct backing_dev_info *bdi = NULL;
|
|
bool wakeup_bdi = false;
|
|
|
|
/*
|
|
* 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)
|
|
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) {
|
|
bdi = inode_to_bdi(inode);
|
|
|
|
if (bdi_cap_writeback_dirty(bdi)) {
|
|
WARN(!test_bit(BDI_registered, &bdi->state),
|
|
"bdi-%s not registered\n", bdi->name);
|
|
|
|
/*
|
|
* 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 (!wb_has_dirty_io(&bdi->wb))
|
|
wakeup_bdi = true;
|
|
}
|
|
|
|
inode->dirtied_when = jiffies;
|
|
list_move(&inode->i_list, &bdi->wb.b_dirty);
|
|
}
|
|
}
|
|
out:
|
|
spin_unlock(&inode_lock);
|
|
|
|
if (wakeup_bdi)
|
|
bdi_wakeup_thread_delayed(bdi);
|
|
}
|
|
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_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);
|