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

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@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Nikolay Borisov <kernel@kyup.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index c9830686cbd503c2bdb99da33579e53e3aa05628..a9d23daa0d6f298e8bc651ca799145ba25fc88df 100644 (file)
--- 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 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
                ret = 0;
                goto retry;
        }
+out:
        mutex_unlock(&inode->i_mutex);
        trace_ext4_fallocate_exit(inode, offset, max_blocks,
                                ret > 0 ? ret2 : ret);