Re: [PATCH] ext4: fix check to prevent false positive report of incorrect used inodes

On 2021/3/29 22:26, Jan Kara wrote:

On Mon 29-03-21 14:19:55, Zhang Yi wrote:

quoted

Commit <50122847007> ("ext4: fix check to prevent initializing reserved
inodes") check the block group zero and prevent initializing reserved
inodes. But in some special cases, the reserved inode may not all belong
to the group zero, it may exist into the second group if we format
filesystem below.

  mkfs.ext4 -b 4096 -g 8192 -N 1024 -I 4096 /dev/sda

So, it will end up triggering a false positive report of a corrupted
file system. This patch fix it by avoid check reserved inodes if no free
inode blocks will be zeroed.

Fixes: 50122847007 ("ext4: fix check to prevent initializing reserved inodes")
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>

Thanks! The patch looks correct but maybe the code can be made more
comprehensible like I suggest below?

quoted

@@ -1543,22 +1544,25 @@ int ext4_init_inode_table(struct super_block *sb, ext4_group_t group,
 	 * used inodes so we need to skip blocks with used inodes in
 	 * inode table.
 	 */
-	if (!(gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)))
-		used_blks = DIV_ROUND_UP((EXT4_INODES_PER_GROUP(sb) -
-			    ext4_itable_unused_count(sb, gdp)),
-			    sbi->s_inodes_per_block);
-
-	if ((used_blks < 0) || (used_blks > sbi->s_itb_per_group) ||
-	    ((group == 0) && ((EXT4_INODES_PER_GROUP(sb) -
-			       ext4_itable_unused_count(sb, gdp)) <
-			      EXT4_FIRST_INO(sb)))) {
-		ext4_error(sb, "Something is wrong with group %u: "
-			   "used itable blocks: %d; "
-			   "itable unused count: %u",
-			   group, used_blks,
-			   ext4_itable_unused_count(sb, gdp));
-		ret = 1;
-		goto err_out;
+	if (!(gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT))) {
+		used_inos = EXT4_INODES_PER_GROUP(sb) -
+			    ext4_itable_unused_count(sb, gdp);
+		used_blks = DIV_ROUND_UP(used_inos, sbi->s_inodes_per_block);
+
+		if (used_blks >= 0 && used_blks <= sbi->s_itb_per_group)
+			used_inos += group * EXT4_INODES_PER_GROUP(sb);

Maybe if would be more comprehensible like:

		/* Bogus inode unused count? */
		if (used_blks < 0 || used_blks > sbi->s_itb_per_group) {
			ext4_error(...);
			ret = 1;
			goto err_out;
		}

		used_inos += EXT4_INODES_PER_GROUP(sb);
		/*
		 * Are there some uninitialized inodes in the inode table
		 * before the first normal inode?
		 */
		if (used_blks != sbi->s_itb_per_group &&
		    used_inos < EXT4_FIRST_INO(sb)) {
			ext4_error(...);
			ret = 1;
			goto err_out;
		}

Yes, it looks more comprehensible, I will send v2 as you suggested.

Thanks,
Yi.