ext4: move check under lock scope to close a race.

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>
Cc: stable@vger.kernel.org

1 files changed, 8 insertions, 7 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 973816bfe4a9..d74e08029643 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4927,13 +4927,6 @@ 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);
 
@@ -4955,6 +4948,14 @@ 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;