linux-kernel - [PATCH 2/4] fs/buffer: avoid redundant lookup in getblk slowpath

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Message-Id: <20250515173925.147823-3-dave@stgolabs.net>
Date: Thu, 15 May 2025 10:39:23 -0700
From: Davidlohr Bueso <dave@...olabs.net>
To: brauner@...nel.org
Cc: jack@...e.cz,
	viro@...iv.linux.org.uk,
	mcgrof@...nel.org,
	dave@...olabs.net,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/4] fs/buffer: avoid redundant lookup in getblk slowpath

__getblk_slow() already implies failing a first lookup
as the fastpath, so try to create the buffers immediately
and avoid the redundant lookup. This saves 5-10% of the
total cost/latency of the slowpath.

Signed-off-by: Davidlohr Bueso <dave@...olabs.net>
---
 fs/buffer.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 5a4342881f3b..b02cced96529 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1139,15 +1139,15 @@ __getblk_slow(struct block_device *bdev, sector_t block,
 	for (;;) {
 		struct buffer_head *bh;
 
+		if (!grow_buffers(bdev, block, size, gfp))
+			return NULL;
+
 		if (blocking)
 			bh = __find_get_block_nonatomic(bdev, block, size);
 		else
 			bh = __find_get_block(bdev, block, size);
 		if (bh)
 			return bh;
-
-		if (!grow_buffers(bdev, block, size, gfp))
-			return NULL;
 	}
 }
 
-- 
2.39.5