ext4: call out CRC and corruption errors with specific error codes

Instead of overloading EIO for CRC errors and corrupt structures,
return the same error codes that XFS returns for the same issues.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c
index 6eb1a61..0a512aa 100644
--- a/fs/ext4/mmp.c
+++ b/fs/ext4/mmp.c
@@ -98,10 +98,12 @@
 	}
 
 	mmp = (struct mmp_struct *)((*bh)->b_data);
-	if (le32_to_cpu(mmp->mmp_magic) == EXT4_MMP_MAGIC &&
-	    ext4_mmp_csum_verify(sb, mmp))
+	if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC)
+		ret = -EFSCORRUPTED;
+	else if (!ext4_mmp_csum_verify(sb, mmp))
+		ret = -EFSBADCRC;
+	else
 		return 0;
-	ret = -EINVAL;
 
 warn_exit:
 	ext4_warning(sb, "Error %d while reading MMP block %llu",