ext4: fix race when setting the bitmap corrupted flag (9af0b3d1) · Commits · 戴 / test

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

fs/ext4/super.c

+11 −11

Original line number	Diff line number	Diff line
		@@ -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)) {
		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);
		set_bit(EXT4_GROUP_INFO_BBITMAP_CORRUPT_BIT,
		&grp->bb_state);
		}

		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);
		}
		}

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