Re: [PATCH 2/5] xfs: fix racy open zone caching

[Damien Le Moal <dlemoal@kernel.org>]

On 2026/08/11 9:48, Christoph Hellwig wrote:
> When testing on very fast storage devices, I've observed writers using
> io_uring creating many open zones with just a few kiB written to it,
> which then don't get used.  I tracked this down to multiple io_uring
> helper threads finding a full zone in i_private, and then going on to
> select a one, with the final one winning the race and leaving it in
> i_private.
> 
> Fix this by dropping full zones from i_private as soon we find them,
> checking cached for a cached zoned when a single writes needs a new zone,
> and by keeping an existing cached zone in xfs_set_cached_zone when it
> still has space available, dropping the newly found/allocated one
> instead.  This uses i_flags_lock as a low-level spinlock for short
> hold times to avoid interactions with the ilock, which is used for
> completions.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks good to me.

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>

-- 
Damien Le Moal
Western Digital Research