ext4: protect bb_first_free in ext4_trim_all_free() with group lock

We should protect reading bd_info->bb_first_free with the group lock
because otherwise we might miss some free blocks. This is not a big deal
at all, but the change to do right thing is really simple, so lets do
that.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 38a11bf79329..396b01f5c4fb 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4825,11 +4825,11 @@ ext4_trim_all_free(struct super_block *sb, ext4_group_t group,
                                 "information for %u", group);
                 return ret;
         }
-
         bitmap = e4b.bd_bitmap;
+
+        ext4_lock_group(sb, group);
         start = (e4b.bd_info->bb_first_free > start) ?
                 e4b.bd_info->bb_first_free : start;
-        ext4_lock_group(sb, group);
 
         while (start < max) {
                 start = mb_find_next_zero_bit(bitmap, max, start);