linux-kernel - Re: [PATCH 2/3] dm bufio: remove redundant __GFP

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Message-ID: <649a5bf8-309b-8128-b3f9-971d3a0bb350@redhat.com>
Date: Mon, 11 Aug 2025 14:44:41 +0200 (CEST)
From: Mikulas Patocka <mpatocka@...hat.com>
To: Qianfeng Rong <rongqianfeng@...o.com>
cc: Alasdair Kergon <agk@...hat.com>, Mike Snitzer <snitzer@...nel.org>, 
    "open list:DEVICE-MAPPER  (LVM)" <dm-devel@...ts.linux.dev>, 
    open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] dm bufio: remove redundant __GFP_NOWARN

Hi

I think that GFP_NOWAIT already includes __GFP_NORETRY too. So, should we 
drop __GFP_NORETRY as well?

Mikulas


On Mon, 11 Aug 2025, Qianfeng Rong wrote:

> GFP_NOWAIT already includes __GFP_NOWARN, so let's remove the redundant
> __GFP_NOWARN.  Also update comments to clarify the flag semantics.
> 
> Signed-off-by: Qianfeng Rong <rongqianfeng@...o.com>
> ---
>  drivers/md/dm-bufio.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
> index ff7595caf440..4b20854e92f5 100644
> --- a/drivers/md/dm-bufio.c
> +++ b/drivers/md/dm-bufio.c
> @@ -1337,7 +1337,7 @@ static void use_bio(struct dm_buffer *b, enum req_op op, sector_t sector,
>  	char *ptr;
>  	unsigned int len;
>  
> -	bio = bio_kmalloc(1, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOWARN);
> +	bio = bio_kmalloc(1, GFP_NOWAIT | __GFP_NORETRY);
>  	if (!bio) {
>  		use_dmio(b, op, sector, n_sectors, offset, ioprio);
>  		return;
> @@ -1601,18 +1601,18 @@ static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client
>  	 * dm-bufio is resistant to allocation failures (it just keeps
>  	 * one buffer reserved in cases all the allocations fail).
>  	 * So set flags to not try too hard:
> -	 *	GFP_NOWAIT: don't wait; if we need to sleep we'll release our
> -	 *		    mutex and wait ourselves.
> +	 *	GFP_NOWAIT: don't wait and don't print a warning in case of
> +	 *		    failure; if we need to sleep we'll release our mutex
> +	 *		    and wait ourselves.
>  	 *	__GFP_NORETRY: don't retry and rather return failure
>  	 *	__GFP_NOMEMALLOC: don't use emergency reserves
> -	 *	__GFP_NOWARN: don't print a warning in case of failure
>  	 *
>  	 * For debugging, if we set the cache size to 1, no new buffers will
>  	 * be allocated.
>  	 */
>  	while (1) {
>  		if (dm_bufio_cache_size_latch != 1) {
> -			b = alloc_buffer(c, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
> +			b = alloc_buffer(c, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC);
>  			if (b)
>  				return b;
>  		}
> -- 
> 2.34.1
>