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From:   Zhang Yi <yi.zhang@huawei.com>
To:     <linux-ext4@vger.kernel.org>
CC:     <tytso@mit.edu>, <adilger.kernel@dilger.ca>, <jack@suse.cz>,
        <yi.zhang@huawei.com>
Subject: [PATCH] ext4: fix check to prevent false positive report of incorrect used inodes
Date:   Mon, 29 Mar 2021 14:19:55 +0800
Message-ID: <20210329061955.2437573-1-yi.zhang@huawei.com>
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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>
---
 fs/ext4/ialloc.c | 36 ++++++++++++++++++++----------------
 1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 633ae7becd61..2eab813b690b 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -1513,6 +1513,7 @@ int ext4_init_inode_table(struct super_block *sb, ext4_group_t group,
 	handle_t *handle;
 	ext4_fsblk_t blk;
 	int num, ret = 0, used_blks = 0;
+	unsigned long used_inos = 0;
 
 	/* This should not happen, but just to be sure check this */
 	if (sb_rdonly(sb)) {
@@ -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);
+
+		if ((used_blks < 0) || (used_blks > sbi->s_itb_per_group) ||
+		    ((used_blks != sbi->s_itb_per_group) &&
+		     (used_inos < 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;
+		}
 	}
 
 	blk = ext4_inode_table(sb, gdp) + used_blks;
-- 
2.25.4