linux-kernel - [PATCH 3.12 06/84] ext4: move check under lock scope to close a race.

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Message-Id: <7e7ec82ecd66ed0cfd77346d8cb4676e06b881ec.1443792303.git.jslaby@suse.cz>
Date:	Fri,  2 Oct 2015 15:24:11 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Davide Italiano <dccitaliano@...il.com>,
	Theodore Ts'o <tytso@....edu>,
	Nikolay Borisov <kernel@...p.com>, Jan Kara <jack@...e.cz>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 06/84] ext4: move check under lock scope to close a race.

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

3.12-stable 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.

[Nikolay Borisov: Bakported to 3.12.47
 - Adjusted context
 - Add the 'out' label]

Signed-off-by: Davide Italiano <dccitaliano@...il.com>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Nikolay Borisov <kernel@...p.com>
Cc: Jan Kara <jack@...e.cz>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 fs/ext4/extents.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index c9830686cbd5..a9d23daa0d6f 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4634,12 +4634,6 @@ 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;
 
 	trace_ext4_fallocate_enter(inode, offset, len, mode);
 	map.m_lblk = offset >> blkbits;
@@ -4654,6 +4648,16 @@ 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);
+
+	/*
+	 * currently supporting (pre)allocate mode for extent-based
+	 * files _only_
+	 */
+	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
+
 	ret = inode_newsize_ok(inode, (len + offset));
 	if (ret) {
 		mutex_unlock(&inode->i_mutex);
@@ -4714,6 +4718,7 @@ retry:
 		ret = 0;
 		goto retry;
 	}
+out:
 	mutex_unlock(&inode->i_mutex);
 	trace_ext4_fallocate_exit(inode, offset, max_blocks,
 				ret > 0 ? ret2 : ret);
-- 
2.6.0

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