ext4: Allow read/only mounts with corrupted block group checksums
If the block group checksums are corrupted, still allow the mount to
succeed, so e2fsck can have a chance to try to fix things up. Add
code in the remount r/w path to make sure the block group checksums
are valid before allowing the filesystem to be remounted read/write.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index b5479b1..876e1c6 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1626,7 +1626,8 @@
"Checksum for group %lu failed (%u!=%u)\n",
i, le16_to_cpu(ext4_group_desc_csum(sbi, i,
gdp)), le16_to_cpu(gdp->bg_checksum));
- return 0;
+ if (!(sb->s_flags & MS_RDONLY))
+ return 0;
}
if (!flexbg_flag)
first_block += EXT4_BLOCKS_PER_GROUP(sb);
@@ -2961,6 +2962,7 @@
ext4_fsblk_t n_blocks_count = 0;
unsigned long old_sb_flags;
struct ext4_mount_options old_opts;
+ ext4_group_t g;
int err;
#ifdef CONFIG_QUOTA
int i;
@@ -3039,6 +3041,26 @@
}
/*
+ * Make sure the group descriptor checksums
+ * are sane. If they aren't, refuse to
+ * remount r/w.
+ */
+ for (g = 0; g < sbi->s_groups_count; g++) {
+ struct ext4_group_desc *gdp =
+ ext4_get_group_desc(sb, g, NULL);
+
+ if (!ext4_group_desc_csum_verify(sbi, g, gdp)) {
+ printk(KERN_ERR
+ "EXT4-fs: ext4_remount: "
+ "Checksum for group %lu failed (%u!=%u)\n",
+ g, le16_to_cpu(ext4_group_desc_csum(sbi, g, gdp)),
+ le16_to_cpu(gdp->bg_checksum));
+ err = -EINVAL;
+ goto restore_opts;
+ }
+ }
+
+ /*
* If we have an unprocessed orphan list hanging
* around from a previously readonly bdev mount,
* require a full umount/remount for now.