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From: NeilBrown <neilb@suse.de>
To: Andrew Morton <akpm@linux-foundation.org>,
	Theodore Ts'o <tytso@mit.edu>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	"Darrick J. Wong" <djwong@kernel.org>,
	Matthew Wilcox <willy@infradead.org>,
	Mel Gorman <mgorman@suse.com>
Cc: linux-xfs@vger.kernel.org, linux-ext4@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: [PATCH 6/6] XFS: remove congestion_wait() loop from xfs_buf_alloc_pages()
Date: Tue, 14 Sep 2021 10:13:04 +1000	[thread overview]
Message-ID: <163157838440.13293.12568710689057349786.stgit@noble.brown> (raw)
In-Reply-To: <163157808321.13293.486682642188075090.stgit@noble.brown>

Documentation commment in gfp.h discourages indefinite retry loops on
ENOMEM and says of __GFP_NOFAIL that it

    is definitely preferable to use the flag rather than opencode
    endless loop around allocator.

congestion_wait() is indistinguishable from
schedule_timeout_uninterruptible() in practice and it is not a good way
to wait for memory to become available.

So instead of waiting, allocate a single page using __GFP_NOFAIL, then
loop around and try to get any more pages that might be needed with a
bulk allocation.  This single-page allocation will wait in the most
appropriate way.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 fs/xfs/xfs_buf.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 5fa6cd947dd4..1ae3768f6504 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -372,8 +372,8 @@ xfs_buf_alloc_pages(
 
 	/*
 	 * Bulk filling of pages can take multiple calls. Not filling the entire
-	 * array is not an allocation failure, so don't back off if we get at
-	 * least one extra page.
+	 * array is not an allocation failure, so don't fail or fall back on
+	 * __GFP_NOFAIL if we get at least one extra page.
 	 */
 	for (;;) {
 		long	last = filled;
@@ -394,7 +394,7 @@ xfs_buf_alloc_pages(
 		}
 
 		XFS_STATS_INC(bp->b_mount, xb_page_retries);
-		congestion_wait(BLK_RW_ASYNC, HZ / 50);
+		bp->b_pages[filled++] = alloc_page(gfp_mask | __GFP_NOFAIL);
 	}
 	return 0;
 }



  parent reply	other threads:[~2021-09-14  0:28 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-14  0:13 [PATCH 0/6] congestion_wait() and GFP_NOFAIL NeilBrown
2021-09-14  0:13 ` [PATCH 2/6] MM: annotate congestion_wait() and wait_iff_congested() as ineffective NeilBrown
2021-09-15 11:56   ` Michal Hocko
2021-09-16 22:13     ` NeilBrown
2021-09-14  0:13 ` [PATCH 5/6] XFS: remove congestion_wait() loop from kmem_alloc() NeilBrown
2021-09-14  1:31   ` Dave Chinner
2021-09-14  3:27     ` NeilBrown
2021-09-14  6:05       ` Dave Chinner
2021-09-14  0:13 ` [PATCH 3/6] EXT4: Remove ENOMEM/congestion_wait() loops NeilBrown
2021-09-14 16:34   ` Mel Gorman
2021-09-14 21:48     ` NeilBrown
2021-09-15 12:06       ` Michal Hocko
2021-09-15 22:35         ` NeilBrown
2021-09-16  0:37           ` Dave Chinner
2021-09-16  6:52           ` Michal Hocko
2021-09-14 23:55     ` Dave Chinner
2021-09-15  8:59       ` Mel Gorman
2021-09-15 12:20         ` Michal Hocko
2021-09-15 14:35         ` Mel Gorman
2021-09-15 22:38           ` Dave Chinner
2021-09-16  9:00             ` Mel Gorman
2021-09-15  0:28   ` Theodore Ts'o
2021-09-15  5:25     ` NeilBrown
2021-09-15 17:02       ` Theodore Ts'o
2021-09-14  0:13 ` [PATCH 1/6] MM: improve documentation for __GFP_NOFAIL NeilBrown
2021-09-15 11:51   ` Michal Hocko
2021-09-14  0:13 ` NeilBrown [this message]
2021-09-14  2:08   ` [PATCH 6/6] XFS: remove congestion_wait() loop from xfs_buf_alloc_pages() Dave Chinner
2021-09-14  2:35     ` NeilBrown
2021-09-14  5:33       ` Dave Chinner
2021-09-14 16:45       ` Mel Gorman
2021-09-14 21:13         ` NeilBrown
2021-09-14  0:13 ` [PATCH 4/6] EXT4: remove congestion_wait from ext4_bio_write_page, and simplify NeilBrown
2021-09-17  2:56 [PATCH 0/6 v2] congestion_wait() and GFP_NOFAIL NeilBrown
2021-09-17  2:56 ` [PATCH 6/6] XFS: remove congestion_wait() loop from xfs_buf_alloc_pages() NeilBrown

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