From: Jchao Sun sunjunchao2870@gmail.com
commit 10e14073107dd0b6d97d9516a02845a8e501c2c9 upstream.
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@gmail.com CC: stable@vger.kernel.org Signed-off-by: Jchao Sun sunjunchao2870@gmail.com Signed-off-by: Jan Kara jack@suse.cz Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/fs-writeback.c | 37 ++++++++++++++++++++++++++++--------- fs/inode.c | 2 +- 2 files changed, 29 insertions(+), 10 deletions(-)
--- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -120,6 +120,7 @@ static bool inode_io_list_move_locked(st 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 li 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 li 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 s * 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 *in { struct super_block *sb = inode->i_sb; int dirtytime = 0; + struct bdi_writeback *wb = NULL;
trace_writeback_mark_inode_dirty(inode, flags);
@@ -2410,13 +2417,24 @@ void __mark_inode_dirty(struct inode *in 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 * the inode it will place it on the appropriate superblock * 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 *in */ 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 *in 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 *in return; } } +out_unlock: + if (wb) + spin_unlock(&wb->list_lock); out_unlock_inode: spin_unlock(&inode->i_lock); } --- a/fs/inode.c +++ b/fs/inode.c @@ -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: