This is a note to let you know that I've just added the patch titled
writeback: Fix inode->i_io_list not be protected by inode->i_lock error
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
writeback-fix-inode-i_io_list-not-be-protected-by-in.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit a6d977e8d36035d60883d72a9a881a77520bfc03
Author: Jchao Sun <sunjunchao2870@xxxxxxxxx>
Date: Tue May 24 08:05:40 2022 -0700
writeback: Fix inode->i_io_list not be protected by inode->i_lock error
[ Upstream commit 10e14073107dd0b6d97d9516a02845a8e501c2c9 ]
Commit b35250c0816c ("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: b35250c0816c ("writeback: Protect inode->i_io_list with inode->i_lock")
Link: https://lore.kernel.org/r/20220524150540.12552-1-sunjunchao2870@xxxxxxxxx
CC: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jchao Sun <sunjunchao2870@xxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Stable-dep-of: cbfecb927f42 ("fs: record I_DIRTY_TIME even if inode already has I_DIRTY_INODE")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 645e3f6ffe44..4c667662a4d9 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -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);
@@ -1282,9 +1283,9 @@ 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))
@@ -1300,7 +1301,12 @@ 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) {
@@ -1726,8 +1732,8 @@ 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;
}
@@ -2265,6 +2271,7 @@ 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);
@@ -2316,6 +2323,17 @@ 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
@@ -2323,7 +2341,7 @@ 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
@@ -2331,22 +2349,19 @@ 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;
@@ -2360,6 +2375,7 @@ 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);
/*
@@ -2374,6 +2390,9 @@ 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);
}
diff --git a/fs/inode.c b/fs/inode.c
index 9f49e0bdc2f7..51726f2ad994 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -28,7 +28,7 @@
* 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:
