linux-kernel - Re: [PATCH][v3] afs: Remove erroneous seq |= 1 in volume lookup loop

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Message-ID: <CAJFZqHxgCcxZL1W8-NtiQjrpvfxmzZ-EdyzCAD6QALqv12LguQ@mail.gmail.com>
Date: Tue, 30 Sep 2025 16:07:39 +0800
From: Li RongQing <roy.qing.li@...il.com>
To: dhowells@...hat.com, marc.dionne@...istor.com, 
	linux-afs@...ts.infradead.org, linux-kernel@...r.kernel.org, oleg@...hat.com, 
	Li RongQing <lirongqing@...du.com>
Subject: Re: [PATCH][v3] afs: Remove erroneous seq |= 1 in volume lookup loop

On Wed, Sep 10, 2025 at 4:42 PM lirongqing <roy.qing.li@...il.com> wrote:
>
> From: Li RongQing <lirongqing@...du.com>
>
> The `seq |= 1` operation in the volume lookup loop is incorrect because:
> seq is already incremented at start, making it odd in next iteration
> which triggers lock, but The `|= 1` operation causes seq to be even
> and unintended lockless operation
>
> Remove this erroneous operation to maintain proper lock sequencing.
>


ping

thanks

-Li


> Fixes: 32222f09782f ("afs: Apply server breaks to mmap'd files in the call processor")
> Reviewed-by: Oleg Nesterov <oleg@...hat.com>
> Signed-off-by: Li RongQing <lirongqing@...du.com>
> ---
> Diff with v2: add Reviewed-by, and Fixes tag
> Diff with v1: rewrite the changelog
>
>  fs/afs/callback.c | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/fs/afs/callback.c b/fs/afs/callback.c
> index 69e1dd5..2c0d274 100644
> --- a/fs/afs/callback.c
> +++ b/fs/afs/callback.c
> @@ -140,7 +140,6 @@ static struct afs_volume *afs_lookup_volume_rcu(struct afs_cell *cell,
>                         break;
>                 if (!need_seqretry(&cell->volume_lock, seq))
>                         break;
> -               seq |= 1; /* Want a lock next time */
>         }
>
>         done_seqretry(&cell->volume_lock, seq);
> --
> 2.9.4
>