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writeback: Fix inode->i_io_list not be protected by inode->i_lock error

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Commit b35250c081 ("writeback: Protect inode->i_io_list with
inode->i_lock") made inode->i_io_list not only protected by
wb->list_lock but also inode->i_lock, but inode_io_list_move_locked()
was missed. Add lock there and also update comment describing
things protected by inode->i_lock. This also fixes a race where
__mark_inode_dirty() could move inode under flush worker's hands
and thus sync(2) could miss writing some inodes.

Fixes: b35250c081 ("writeback: Protect inode->i_io_list with inode->i_lock")
Link: https://lore.kernel.org/r/20220524150540.12552-1-sunjunchao2870@gmail.com
CC: stable@vger.kernel.org
Signed-off-by: Jchao Sun <sunjunchao2870@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Jchao Sun 2022-05-24 08:05:40 -07:00 committed by Jan Kara
parent 2aab03b867
commit 10e1407310
2 changed files with 29 additions and 10 deletions
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37
fs/fs-writeback.c
View File

@ -120,6 +120,7 @@ static bool inode_io_list_move_locked(struct inode *inode,
struct list_head *head)
{
assert_spin_locked(&wb->list_lock);
assert_spin_locked(&inode->i_lock);
list_move(&inode->i_io_list, head);
@ -1365,9 +1366,9 @@ static int move_expired_inodes(struct list_head *delaying_queue,
inode = wb_inode(delaying_queue->prev);
if (inode_dirtied_after(inode, dirtied_before))
break;
spin_lock(&inode->i_lock);
list_move(&inode->i_io_list, &tmp);
moved++;
spin_lock(&inode->i_lock);
inode->i_state |= I_SYNC_QUEUED;
spin_unlock(&inode->i_lock);
if (sb_is_blkdev_sb(inode->i_sb))
@ -1383,7 +1384,12 @@ static int move_expired_inodes(struct list_head *delaying_queue,
goto out;
}
/* Move inodes from one superblock together */
/*
* Although inode's i_io_list is moved from 'tmp' to 'dispatch_queue',
* we don't take inode->i_lock here because it is just a pointless overhead.
* Inode is already marked as I_SYNC_QUEUED so writeback list handling is
* fully under our control.
*/
while (!list_empty(&tmp)) {
sb = wb_inode(tmp.prev)->i_sb;
list_for_each_prev_safe(pos, node, &tmp) {
@ -1826,8 +1832,8 @@ static long writeback_sb_inodes(struct super_block *sb,
* We'll have another go at writing back this inode
* when we completed a full scan of b_io.
*/
spin_unlock(&inode->i_lock);
requeue_io(inode, wb);
spin_unlock(&inode->i_lock);
trace_writeback_sb_inodes_requeue(inode);
continue;
}
@ -2358,6 +2364,7 @@ void __mark_inode_dirty(struct inode *inode, int flags)
{
struct super_block *sb = inode->i_sb;
int dirtytime = 0;
struct bdi_writeback *wb = NULL;
trace_writeback_mark_inode_dirty(inode, flags);
@ -2409,6 +2416,17 @@ void __mark_inode_dirty(struct inode *inode, int flags)
inode->i_state &= ~I_DIRTY_TIME;
inode->i_state |= flags;
/*
* Grab inode's wb early because it requires dropping i_lock and we
* need to make sure following checks happen atomically with dirty
* list handling so that we don't move inodes under flush worker's
* hands.
*/
if (!was_dirty) {
wb = locked_inode_to_wb_and_lock_list(inode);
spin_lock(&inode->i_lock);
}
/*
* If the inode is queued for writeback by flush worker, just
* update its dirty state. Once the flush worker is done with
@ -2416,7 +2434,7 @@ void __mark_inode_dirty(struct inode *inode, int flags)
* list, based upon its state.
*/
if (inode->i_state & I_SYNC_QUEUED)
goto out_unlock_inode;
goto out_unlock;
/*
* Only add valid (hashed) inodes to the superblock's
@ -2424,22 +2442,19 @@ void __mark_inode_dirty(struct inode *inode, int flags)
*/
if (!S_ISBLK(inode->i_mode)) {
if (inode_unhashed(inode))
goto out_unlock_inode;
goto out_unlock;
}
if (inode->i_state & I_FREEING)
goto out_unlock_inode;
goto out_unlock;
/*
* If the inode was already on b_dirty/b_io/b_more_io, don't
* reposition it (that would break b_dirty time-ordering).
*/
if (!was_dirty) {
struct bdi_writeback *wb;
struct list_head *dirty_list;
bool wakeup_bdi = false;
wb = locked_inode_to_wb_and_lock_list(inode);
inode->dirtied_when = jiffies;
if (dirtytime)
inode->dirtied_time_when = jiffies;
@ -2453,6 +2468,7 @@ void __mark_inode_dirty(struct inode *inode, int flags)
dirty_list);
spin_unlock(&wb->list_lock);
spin_unlock(&inode->i_lock);
trace_writeback_dirty_inode_enqueue(inode);
/*
@ -2467,6 +2483,9 @@ void __mark_inode_dirty(struct inode *inode, int flags)
return;
}
}
out_unlock:
if (wb)
spin_unlock(&wb->list_lock);
out_unlock_inode:
spin_unlock(&inode->i_lock);
}

2
fs/inode.c
View File

@ -27,7 +27,7 @@
* Inode locking rules:
*
* inode->i_lock protects:
* inode->i_state, inode->i_hash, __iget()
* inode->i_state, inode->i_hash, __iget(), inode->i_io_list
* Inode LRU list locks protect:
* inode->i_sb->s_inode_lru, inode->i_lru
* inode->i_sb->s_inode_list_lock protects: