linux-ext4 - [PATCH v2 3/5] ext4: fix wrong m_len value after unwritten extent conversion

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Message-Id: <1362579435-6333-4-git-send-email-wenqing.lz@taobao.com>
Date:	Wed,  6 Mar 2013 22:17:13 +0800
From:	Zheng Liu <gnehzuil.liu@...il.com>
To:	linux-ext4@...r.kernel.org
Cc:	Zheng Liu <wenqing.lz@...bao.com>, "Theodore Ts'o" <tytso@....edu>,
	Dmitry Monakhov <dmonakhov@...nvz.org>
Subject: [PATCH v2 3/5] ext4: fix wrong m_len value after unwritten extent conversion

From: Zheng Liu <wenqing.lz@...bao.com>

We always assume that the return value of ext4_ext_map_blocks is equal
to map->m_len but when we try to convert an unwritten extent 'm_len'
value will break this assumption.  It is harmless until we use status
tree as a extent cache because we need to update status tree according
to 'm_len' value.

Meanwhile this commit marks EXT4_MAP_MAPPED flag after unwritten extent
conversion.  It shouldn't cause a bug because we update status tree
according to checking EXT4_MAP_UNWRITTEN flag.  But it should be fixed.

After applied this commit, the following error message from self-testing
infrastructure disappears.

    ...
    kernel: ES len assertation failed for inode: 230 retval 1 !=
    map->m_len 3 in ext4_map_blocks (allocation)
    ...

Signed-off-by: Zheng Liu <wenqing.lz@...bao.com>
Cc: "Theodore Ts'o" <tytso@....edu>
Cc: Dmitry Monakhov <dmonakhov@...nvz.org>
---
 fs/ext4/extents.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 25c86aa..110e85a 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3650,6 +3650,10 @@ ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
 						 path, map->m_len);
 		} else
 			err = ret;
+		map->m_flags |= EXT4_MAP_MAPPED;
+		if (allocated > map->m_len)
+			allocated = map->m_len;
+		map->m_len = allocated;
 		goto out2;
 	}
 	/* buffered IO case */
-- 
1.7.12.rc2.18.g61b472e

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