linux-kernel - [PATCH 3.16.y-ckt 034/129] ext4: move check under lock scope to close a race.

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Message-Id: <1432285114-9254-35-git-send-email-luis.henriques@canonical.com>
Date:	Fri, 22 May 2015 09:56:59 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Davide Italiano <dccitaliano@...il.com>,
	Theodore Ts'o <tytso@....edu>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 034/129] ext4: move check under lock scope to close a race.

3.16.7-ckt12 -stable review patch.  If anyone has any objections, please let me know.

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

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

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>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 fs/ext4/extents.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index cdfe574ba3d9..99d74306e770 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4933,13 +4933,6 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 	if (ret)
 		return ret;
 
-	/*
-	 * currently supporting (pre)allocate mode for extent-based
-	 * files _only_
-	 */
-	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
-		return -EOPNOTSUPP;
-
 	if (mode & FALLOC_FL_COLLAPSE_RANGE)
 		return ext4_collapse_range(inode, offset, len);
 
@@ -4961,6 +4954,14 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 
 	mutex_lock(&inode->i_mutex);
 
+	/*
+	 * We only support preallocation for extent-based files only
+	 */
+	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
+
 	if (!(mode & FALLOC_FL_KEEP_SIZE) &&
 	     offset + len > i_size_read(inode)) {
 		new_size = offset + len;
--
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