linux-ext4 - Re: [PATCH] ext4: add __GFP_NOWARN to GFP

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Date:   Tue, 24 Oct 2023 12:03:18 +0200
From:   Jan Kara <jack@...e.cz>
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Hui Zhu <teawater@...group.com>, Jan Kara <jack@...e.cz>,
        Theodore Ts'o <tytso@....edu>, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] ext4: add __GFP_NOWARN to GFP_NOWAIT in readahead

On Mon 23-10-23 23:26:08, Hugh Dickins wrote:
> Since mm-hotfixes-stable commit e509ad4d77e6 ("ext4: use bdev_getblk() to
> avoid memory reclaim in readahead path") rightly replaced GFP_NOFAIL
> allocations by GFP_NOWAIT allocations, I've occasionally been seeing
> "page allocation failure: order:0" warnings under load: all with
> ext4_sb_breadahead_unmovable() in the stack.  I don't think those
> warnings are of any interest: suppress them with __GFP_NOWARN.
> 
> Fixes: e509ad4d77e6 ("ext4: use bdev_getblk() to avoid memory reclaim in readahead path")
> Signed-off-by: Hugh Dickins <hughd@...gle.com>

Yeah, makes sense. Just the commit you mention isn't upstream yet so I'm
not sure whether the commit hash is stable. I guess something for Andrew to
figure out. In any case feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/ext4/super.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index c00ec159dea5..56a08fc5c5d5 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -262,7 +262,7 @@ struct buffer_head *ext4_sb_bread_unmovable(struct super_block *sb,
>  void ext4_sb_breadahead_unmovable(struct super_block *sb, sector_t block)
>  {
>  	struct buffer_head *bh = bdev_getblk(sb->s_bdev, block,
> -			sb->s_blocksize, GFP_NOWAIT);
> +			sb->s_blocksize, GFP_NOWAIT | __GFP_NOWARN);
>  
>  	if (likely(bh)) {
>  		if (trylock_buffer(bh))
> -- 
> 2.35.3
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR