linux-ext4 - [PATCH] ext4: fix error when itable blocks is greater than s_itb_per

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Date:   Tue,  2 Aug 2022 10:10:29 +0800
From:   Michael Wu <michael@...winnertech.com>
To:     tytso@....edu, adilger.kernel@...ger.ca
Cc:     linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        allwinner-opensource-support@...winnertech.com
Subject: [PATCH] ext4: fix error when itable blocks is greater than s_itb_per_group

The following error occurs when mounting the ext4 image made by image
making tool:
"ext4_init_inode_table:1301:comm ext4lazyinit:Something is wrong with group
0: used itable blocks: 491; itable unused count: 0."

Currently all the inodes in block group0 and ext4 image is divided by
s_inodes_per_group. That leads to a hazard: we can't ensure all
s_inodes_per_group are divisible by s_inodes_per_block. For example, when
the s_inodes_per_group (equals to 7851) is divided by s_inodes_per_block
(which is 16), because 7851 is undivisible by 16, we get the wrong result
490, while 491 is expected.

So, we suggest that s_itb_per_group should equal to
DIV_ROUND_UP(s_inodes_per_group, s_inodes_per_block) instead of directly
getting the result from s_inodes_per_group/s_inodes_per_block.

Signed-off-by: Michael Wu <michael@...winnertech.com>
---
 fs/ext4/super.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 845f2f8aee5f..76cbd638ea10 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4796,8 +4796,8 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 			 sbi->s_inodes_per_group);
 		goto failed_mount;
 	}
-	sbi->s_itb_per_group = sbi->s_inodes_per_group /
-					sbi->s_inodes_per_block;
+	sbi->s_itb_per_group = DIV_ROUND_UP(sbi->s_inodes_per_group,
+					    sbi->s_inodes_per_block);
 	sbi->s_desc_per_block = blocksize / EXT4_DESC_SIZE(sb);
 	sbi->s_sbh = bh;
 	sbi->s_mount_state = le16_to_cpu(es->s_state) & ~EXT4_FC_REPLAY;
-- 
2.29.0