[PATCH] ext4: skip i_extra_isize expansion during inode eviction

[Helen Koike]

__ext4_mark_inode_dirty may be called from the eviction/free path (via
ext4_truncate → ext4_ext_truncate → mark_inode_dirty), which may call
ext4_try_to_expand_extra_isize() that could create a new EA inode,
wasting work that will be immediately discarded.

Skip the expansion when the inode is transitioning to freed.

Signed-off-by: Helen Koike <koike@xxxxxxxxxx>
---

Hello,

I saw this while investigating the syzbot issue (see the stack trace of
unlink "-> #0"):
   https://syzkaller.appspot.com/bug?extid=d91a6e2efb07bd3354e9

While the reported issue is fixed by:
  7f473f971382 ("ext4: lockdep: handle i_data_sem subclassing for special inodes")
I believe the call to ext4_try_to_expand_extra_isize() in the eviction
path doesn't make sense in the first place.

I understand this is not a major optimization, so not a high priority,
but sending it anyway in case anyone finds it useful.
---
 fs/ext4/inode.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index ce99807c5f5b..cea3405cd841 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -6603,7 +6603,8 @@ int __ext4_mark_inode_dirty(handle_t *handle, struct inode *inode,
 	if (err)
 		goto out;
 
-	if (EXT4_I(inode)->i_extra_isize < sbi->s_want_extra_isize)
+	if (EXT4_I(inode)->i_extra_isize < sbi->s_want_extra_isize &&
+	    !(inode_state_read_once(inode) & (I_FREEING | I_WILL_FREE)))
 		ext4_try_to_expand_extra_isize(inode, sbi->s_want_extra_isize,
 					       iloc, handle);
 
-- 
2.54.0