linux-kernel - [PATCH 3.4 069/146] ext4: move check under lock scope to close a race.

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Message-Id: <1442307861-32031-69-git-send-email-lizf@kernel.org>
Date:	Tue, 15 Sep 2015 17:03:04 +0800
From:	lizf@...nel.org
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Davide Italiano <dccitaliano@...il.com>,
	Theodore Ts'o <tytso@....edu>, Zefan Li <lizefan@...wei.com>
Subject: [PATCH 3.4 069/146] ext4: move check under lock scope to close a race.

From: Davide Italiano <dccitaliano@...il.com>

3.4.109-rc1 review patch.  If anyone has any objections, please let me know.

------------------


commit 280227a75b56ab5d35854f3a77ef74a7ad56a203 upstream.

fallocate() checks that the file is extent-based and returns
EOPNOTSUPP in case is not. Other tasks can convert from and to
indirect and extent so it's safe to check only after grabbing
the inode mutex.

Signed-off-by: Davide Italiano <dccitaliano@...il.com>
Signed-off-by: Theodore Ts'o <tytso@....edu>
[lizf: Backported to 3.4:
 - adjust context
 - return -EOPNOTSUPP instead of jumping to the "out" label]
Signed-off-by: Zefan Li <lizefan@...wei.com>
---
 fs/ext4/extents.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 4296a6f..bb72833 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4365,13 +4365,6 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 	struct ext4_map_blocks map;
 	unsigned int credits, blkbits = inode->i_blkbits;
 
-	/*
-	 * currently supporting (pre)allocate mode for extent-based
-	 * files _only_
-	 */
-	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
-		return -EOPNOTSUPP;
-
 	/* Return error if mode is not supported */
 	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
 		return -EOPNOTSUPP;
@@ -4392,6 +4385,15 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 	 */
 	credits = ext4_chunk_trans_blocks(inode, max_blocks);
 	mutex_lock(&inode->i_mutex);
+
+	/*
+	 * We only support preallocation for extent-based files only
+	 */
+	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
+		mutex_unlock(&inode->i_mutex);
+		return -EOPNOTSUPP;
+	}
+
 	ret = inode_newsize_ok(inode, (len + offset));
 	if (ret) {
 		mutex_unlock(&inode->i_mutex);
-- 
1.9.1

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