ext4: avoid dividing by 0 in mb_update_avg_fragment_size() when block bitmap corrupt

Determine if bb_fragments is 0 instead of determining bb_free to eliminate
the risk of dividing by zero when the block bitmap is corrupted.

Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20240104142040.2835097-6-libaokun1@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index fa351aa323dcf2ec4a3ce8ddb687eca62aa9a70a..751e31df0f10477d66a4004d56d94b24ee8056e7 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -842,7 +842,7 @@ mb_update_avg_fragment_size(struct super_block *sb, struct ext4_group_info *grp)
        struct ext4_sb_info *sbi = EXT4_SB(sb);
        int new_order;
 
-       if (!test_opt2(sb, MB_OPTIMIZE_SCAN) || grp->bb_free == 0)
+       if (!test_opt2(sb, MB_OPTIMIZE_SCAN) || grp->bb_fragments == 0)
                return;
 
        new_order = mb_avg_fragment_size_order(sb,