linux-kernel - [PATCH -next v2 6/7] ext4: simply the mapping query logic in ext4_iomap

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Message-ID: <20251223011802.31238-7-yi.zhang@huaweicloud.com>
Date: Tue, 23 Dec 2025 09:18:01 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: linux-ext4@...r.kernel.org
Cc: linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	tytso@....edu,
	adilger.kernel@...ger.ca,
	jack@...e.cz,
	ojaswin@...ux.ibm.com,
	ritesh.list@...il.com,
	yi.zhang@...wei.com,
	yi.zhang@...weicloud.com,
	yizhang089@...il.com,
	libaokun1@...wei.com,
	yangerkun@...wei.com,
	yukuai@...as.com
Subject: [PATCH -next v2 6/7] ext4: simply the mapping query logic in ext4_iomap_begin()

From: Zhang Yi <yi.zhang@...wei.com>

In the write path mapping check of ext4_iomap_begin(), the return value
'ret' should never greater than orig_mlen. If 'ret' equals 'orig_mlen',
it can be returned directly without checking IOMAP_ATOMIC.

Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
Reviewed-by: Jan Kara <jack@...e.cz>
---
 fs/ext4/inode.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index b84a2a10dfb8..67fe7d0f47e3 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3816,17 +3816,19 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
 		if (offset + length <= i_size_read(inode)) {
 			ret = ext4_map_blocks(NULL, inode, &map, 0);
 			/*
-			 * For atomic writes the entire requested length should
-			 * be mapped. For DAX we convert extents to initialized
-			 * ones before copying the data, otherwise we do it
-			 * after I/O so there's no need to call into
-			 * ext4_iomap_alloc().
+			 * For DAX we convert extents to initialized ones before
+			 * copying the data, otherwise we do it after I/O so
+			 * there's no need to call into ext4_iomap_alloc().
 			 */
 			if ((map.m_flags & EXT4_MAP_MAPPED) ||
 			    (!(flags & IOMAP_DAX) &&
 			     (map.m_flags & EXT4_MAP_UNWRITTEN))) {
-				if ((!(flags & IOMAP_ATOMIC) && ret > 0) ||
-				   (flags & IOMAP_ATOMIC && ret >= orig_mlen))
+				/*
+				 * For atomic writes the entire requested
+				 * length should be mapped.
+				 */
+				if (ret == orig_mlen ||
+				    (!(flags & IOMAP_ATOMIC) && ret > 0))
 					goto out;
 			}
 			map.m_len = orig_mlen;
-- 
2.52.0