linux-ext4 - [RFC PATCH v3 10/26] ext4: correct delalloc extent length

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Date: Sat, 27 Jan 2024 09:58:09 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: linux-ext4@...r.kernel.org
Cc: linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	tytso@....edu,
	adilger.kernel@...ger.ca,
	jack@...e.cz,
	ritesh.list@...il.com,
	hch@...radead.org,
	djwong@...nel.org,
	willy@...radead.org,
	zokeefe@...gle.com,
	yi.zhang@...wei.com,
	yi.zhang@...weicloud.com,
	chengzhihao1@...wei.com,
	yukuai3@...wei.com,
	wangkefeng.wang@...wei.com
Subject: [RFC PATCH v3 10/26] ext4: correct delalloc extent length

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

When adding a delalloc extent in ext4_da_map_blocks(), the extent
length can be incorrect if we found a cached hole extent entry and the
hole length is smaller than the origin map->m_len. Fortunately, it
should not be able to trigger any issue now because the map->m_len is
always 1. Fix this by adjust length before inserting delalloc extent.

Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
---
 fs/ext4/inode.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index bc29c2e92750..44033828db44 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1712,6 +1712,11 @@ static int ext4_da_map_blocks(struct inode *inode, sector_t iblock,
 
 	/* Lookup extent status tree firstly */
 	if (ext4_es_lookup_extent(inode, iblock, NULL, &es)) {
+		retval = es.es_len - (iblock - es.es_lblk);
+		if (retval > map->m_len)
+			retval = map->m_len;
+		map->m_len = retval;
+
 		if (ext4_es_is_hole(&es))
 			goto add_delayed;
 
@@ -1727,10 +1732,6 @@ static int ext4_da_map_blocks(struct inode *inode, sector_t iblock,
 		}
 
 		map->m_pblk = ext4_es_pblock(&es) + iblock - es.es_lblk;
-		retval = es.es_len - (iblock - es.es_lblk);
-		if (retval > map->m_len)
-			retval = map->m_len;
-		map->m_len = retval;
 		if (ext4_es_is_written(&es))
 			map->m_flags |= EXT4_MAP_MAPPED;
 		else if (ext4_es_is_unwritten(&es))
-- 
2.39.2