linux-kernel - [PATCH V3] iomap: skip unnecessary ifs_block_is

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Message-Id: <20250410071236.16017-1-gouhao@uniontech.com>
Date: Thu, 10 Apr 2025 15:12:36 +0800
From: Gou Hao <gouhao@...ontech.com>
To: gouhao@...ontech.com,
	brauner@...nel.org,
	djwong@...nel.org,
	hch@...radead.org
Cc: gouhaojake@....com,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-xfs@...r.kernel.org,
	wangyuli@...ontech.com
Subject: [PATCH V3] iomap: skip unnecessary ifs_block_is_uptodate check

In iomap_adjust_read_range, i is either the first !uptodate block, or it
is past last for the second loop looking for trailing uptodate blocks.
Assuming there's no overflow (there's no combination of huge folios and
tiny blksize) then yeah, there is no point in retesting that the same
block pointed to by i is uptodate since we hold the folio lock so nobody
else could have set it uptodate.

Signed-off-by: Gou Hao <gouhao@...ontech.com>
Reviewed-by: "Darrick J. Wong" <djwong@...nel.org>
Suggested-by: Christoph Hellwig <hch@...radead.org>
---
 fs/iomap/buffered-io.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Changes:
V3:
- optimize commit log
- change 'for' to 'while'

V2:
- optimize commit log

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 31553372b33a..5b08bd417b28 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -259,7 +259,7 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
 		}
 
 		/* truncate len if we find any trailing uptodate block(s) */
-		for ( ; i <= last; i++) {
+		while (++i <= last) {
 			if (ifs_block_is_uptodate(ifs, i)) {
 				plen -= (last - i + 1) * block_size;
 				last = i - 1;
-- 
2.20.1