Re: [PATCH] loop: don't print warnings if the underlying filesystem doesn't support discard

[Ming Lei <ming.lei@redhat.com>]

On Thu, Sep 23, 2021 at 03:48:27PM -0400, Mikulas Patocka wrote:
> Hi
> 
> When running the lvm testsuite, we get a lot of warnings 
> "blk_update_request: operation not supported error, dev loop0, sector 0 op 
> 0x9:(WRITE_ZEROES) flags 0x800800 phys_seg 0 prio class 0". The lvm 
> testsuite puts the loop device on tmpfs and the reason for the warning is 
> that tmpfs supports fallocate, but doesn't support FALLOC_FL_ZERO_RANGE.
> 
> I've created this patch to silence the warnings.
> 
> Mikulas
> 
> 
> 
> From: Mikulas Patocka <mpatocka@redhat.com>
> 
> The loop driver checks for the fallocate method and if it is present, it
> assumes that the filesystem can do FALLOC_FL_ZERO_RANGE and
> FALLOC_FL_PUNCH_HOLE requests. However, some filesystems (such as fat, or
> tmpfs) have the fallocate method, but lack the capability to do
> FALLOC_FL_ZERO_RANGE and/or FALLOC_FL_PUNCH_HOLE.
> 
> This results in syslog warnings "blk_update_request: operation not
> supported error, dev loop0, sector 0 op 0x9:(WRITE_ZEROES) flags 0x800800
> phys_seg 0 prio class 0"
> 
> This patch sets RQF_QUIET to silence the warnings.
> 
> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
> Cc: stable@vger.kernel.org
> 
> ---
>  drivers/block/loop.c |   11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> Index: linux-2.6/drivers/block/loop.c
> ===================================================================
> --- linux-2.6.orig/drivers/block/loop.c	2021-09-23 17:06:57.000000000 +0200
> +++ linux-2.6/drivers/block/loop.c	2021-09-23 21:29:39.000000000 +0200
> @@ -493,7 +493,16 @@ static int lo_fallocate(struct loop_devi
>  	ret = file->f_op->fallocate(file, mode, pos, blk_rq_bytes(rq));
>  	if (unlikely(ret && ret != -EINVAL && ret != -EOPNOTSUPP))
>  		ret = -EIO;
> - out:
> +out:
> +
> +	/*
> +	 * Some filesystems have the fallocate method, but lack the capability
> +	 * to do FALLOC_FL_ZERO_RANGE and/or FALLOC_FL_PUNCH_HOLE requests.
> +	 * We do not want a syslog warning in this case.
> +	 */
> +	if (ret == -EOPNOTSUPP)
> +		rq->rq_flags |= RQF_QUIET;
> +

Looks fine,

Reviewed-by: Ming Lei <ming.lei@redhat.com>

-- 
Ming