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

lizf
2015-09-15T09:36:44Z

From: Davide Italiano <dccitaliano@gmail.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@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
[lizf: Backported to 3.4:
- adjust context
- return -EOPNOTSUPP instead of jumping to the "out" label]
Signed-off-by: Zefan Li <lizefan@huawei.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