Re: [bug report] fstests generic/774 hang again

[Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>]

On Sep 16, 2026 / 11:23, John Garry wrote:
[...]
> We could try something like this:
> 
> ----8<------
> 
> [PATCH] xfs: serialize CoW-based atomic writes
> 
> We have had reports of system hangs when testing Cow-based atomic writes
> for large block sizes.
> 
> Analysis has shown large contention on the the per-inode ilock,
> superficially in creating the mapping in
> xfs_atomic_write_cow_iomap_begin().
> 
> Serialize atomic writes to reduce this contention. In some cases this may
> reduce performance, but high performance has not been a requirement so far
> for CoW-based atomic writes.
> 
> Signed-off-by: John Garry <john.garry@linux.dev>
[...]
> ---->8------
> 
> This is far from ideal, but I think that it should stops the hangs - having
> the kernel hang is intolerable.

Thanks. I applied the patch on top of xfs/for-next branch commit 0ca15a1a1151,
then repeated the test case 100 times on top of the kernel. I did not observe
the hang. This patch looks avoiding the hang.