ext4: fix race when setting the bitmap corrupted flag

Whenever we hit block or inode bitmap corruptions we set
bit and then reduce this block group free inode/clusters
counter to expose right available space.

However some of ext4_mark_group_bitmap_corrupted() is called
inside group spinlock, some are not, this could make it happen
that we double reduce one block group free counters from system.

Always hold group spinlock for it could fix it, but it looks
a little heavy, we could use test_and_set_bit() to fix race
problems here.

Signed-off-by: Wang Shilong <wshilong@ddn.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index d4a218ba626cbcd83abbc23190cc69e63357967e..f7750bc5b85aa6a6f34d819a93ae188d24728227 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -795,26 +795,26 @@ void ext4_mark_group_bitmap_corrupted(struct super_block *sb,
        struct ext4_sb_info *sbi = EXT4_SB(sb);
        struct ext4_group_info *grp = ext4_get_group_info(sb, group);
        struct ext4_group_desc *gdp = ext4_get_group_desc(sb, group, NULL);
+       int ret;
 
-       if ((flags & EXT4_GROUP_INFO_BBITMAP_CORRUPT) &&
-           !EXT4_MB_GRP_BBITMAP_CORRUPT(grp)) {
-               percpu_counter_sub(&sbi->s_freeclusters_counter,
-                                       grp->bb_free);
-               set_bit(EXT4_GROUP_INFO_BBITMAP_CORRUPT_BIT,
-                       &grp->bb_state);
+       if (flags & EXT4_GROUP_INFO_BBITMAP_CORRUPT) {
+               ret = ext4_test_and_set_bit(EXT4_GROUP_INFO_BBITMAP_CORRUPT_BIT,
+                                           &grp->bb_state);
+               if (!ret)
+                       percpu_counter_sub(&sbi->s_freeclusters_counter,
+                                          grp->bb_free);
        }
 
-       if ((flags & EXT4_GROUP_INFO_IBITMAP_CORRUPT) &&
-           !EXT4_MB_GRP_IBITMAP_CORRUPT(grp)) {
-               if (gdp) {
+       if (flags & EXT4_GROUP_INFO_IBITMAP_CORRUPT) {
+               ret = ext4_test_and_set_bit(EXT4_GROUP_INFO_IBITMAP_CORRUPT_BIT,
+                                           &grp->bb_state);
+               if (!ret && gdp) {
                        int count;
 
                        count = ext4_free_inodes_count(sb, gdp);
                        percpu_counter_sub(&sbi->s_freeinodes_counter,
                                           count);
                }
-               set_bit(EXT4_GROUP_INFO_IBITMAP_CORRUPT_BIT,
-                       &grp->bb_state);
        }
 }