ext4: make block group checksums use metadata_csum algorithm

metadata_csum supersedes uninit_bg.  Convert the ROCOMPAT uninit_bg
flag check to a helper function that covers both, and make the
checksum calculation algorithm use either crc16 or the metadata_csum
chosen algorithm depending on which flag is set.  Print a warning if
we try to mount a filesystem with both feature flags set.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 57 insertions, 24 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index f80c7e61282..c18c5968cd9 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1952,43 +1952,69 @@ failed:
 	return 0;
 }
 
-__le16 ext4_group_desc_csum(struct ext4_sb_info *sbi, __u32 block_group,
-			    struct ext4_group_desc *gdp)
+static __le16 ext4_group_desc_csum(struct ext4_sb_info *sbi, __u32 block_group,
+				   struct ext4_group_desc *gdp)
 {
+	int offset;
 	__u16 crc = 0;
+	__le32 le_group = cpu_to_le32(block_group);
 
-	if (sbi->s_es->s_feature_ro_compat &
-	    cpu_to_le32(EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
-		int offset = offsetof(struct ext4_group_desc, bg_checksum);
-		__le32 le_group = cpu_to_le32(block_group);
-
-		crc = crc16(~0, sbi->s_es->s_uuid, sizeof(sbi->s_es->s_uuid));
-		crc = crc16(crc, (__u8 *)&le_group, sizeof(le_group));
-		crc = crc16(crc, (__u8 *)gdp, offset);
-		offset += sizeof(gdp->bg_checksum); /* skip checksum */
-		/* for checksum of struct ext4_group_desc do the rest...*/
-		if ((sbi->s_es->s_feature_incompat &
-		     cpu_to_le32(EXT4_FEATURE_INCOMPAT_64BIT)) &&
-		    offset < le16_to_cpu(sbi->s_es->s_desc_size))
-			crc = crc16(crc, (__u8 *)gdp + offset,
-				    le16_to_cpu(sbi->s_es->s_desc_size) -
-					offset);
+	if ((sbi->s_es->s_feature_ro_compat &
+	     cpu_to_le32(EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))) {
+		/* Use new metadata_csum algorithm */
+		__u16 old_csum;
+		__u32 csum32;
+
+		old_csum = gdp->bg_checksum;
+		gdp->bg_checksum = 0;
+		csum32 = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&le_group,
+				     sizeof(le_group));
+		csum32 = ext4_chksum(sbi, csum32, (__u8 *)gdp,
+				     sbi->s_desc_size);
+		gdp->bg_checksum = old_csum;
+
+		crc = csum32 & 0xFFFF;
+		goto out;
 	}
 
+	/* old crc16 code */
+	offset = offsetof(struct ext4_group_desc, bg_checksum);
+
+	crc = crc16(~0, sbi->s_es->s_uuid, sizeof(sbi->s_es->s_uuid));
+	crc = crc16(crc, (__u8 *)&le_group, sizeof(le_group));
+	crc = crc16(crc, (__u8 *)gdp, offset);
+	offset += sizeof(gdp->bg_checksum); /* skip checksum */
+	/* for checksum of struct ext4_group_desc do the rest...*/
+	if ((sbi->s_es->s_feature_incompat &
+	     cpu_to_le32(EXT4_FEATURE_INCOMPAT_64BIT)) &&
+	    offset < le16_to_cpu(sbi->s_es->s_desc_size))
+		crc = crc16(crc, (__u8 *)gdp + offset,
+			    le16_to_cpu(sbi->s_es->s_desc_size) -
+				offset);
+
+out:
 	return cpu_to_le16(crc);
 }
 
-int ext4_group_desc_csum_verify(struct ext4_sb_info *sbi, __u32 block_group,
+int ext4_group_desc_csum_verify(struct super_block *sb, __u32 block_group,
 				struct ext4_group_desc *gdp)
 {
-	if ((sbi->s_es->s_feature_ro_compat &
-	     cpu_to_le32(EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) &&
-	    (gdp->bg_checksum != ext4_group_desc_csum(sbi, block_group, gdp)))
+	if (ext4_has_group_desc_csum(sb) &&
+	    (gdp->bg_checksum != ext4_group_desc_csum(EXT4_SB(sb),
+						      block_group, gdp)))
 		return 0;
 
 	return 1;
 }
 
+void ext4_group_desc_csum_set(struct super_block *sb, __u32 block_group,
+			      struct ext4_group_desc *gdp)
+{
+	if (!ext4_has_group_desc_csum(sb))
+		return;
+	gdp->bg_checksum = ext4_group_desc_csum(EXT4_SB(sb), block_group, gdp);
+}
+
 /* Called at mount-time, super-block is locked */
 static int ext4_check_descriptors(struct super_block *sb,
 				  ext4_group_t *first_not_zeroed)
@@ -2043,7 +2069,7 @@ static int ext4_check_descriptors(struct super_block *sb,
 			return 0;
 		}
 		ext4_lock_group(sb, i);
-		if (!ext4_group_desc_csum_verify(sbi, i, gdp)) {
+		if (!ext4_group_desc_csum_verify(sb, i, gdp)) {
 			ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
 				 "Checksum for group %u failed (%u!=%u)",
 				 i, le16_to_cpu(ext4_group_desc_csum(sbi, i,
@@ -3069,6 +3095,13 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		goto cantfind_ext4;
 	sbi->s_kbytes_written = le64_to_cpu(es->s_kbytes_written);
 
+	/* Warn if metadata_csum and gdt_csum are both set. */
+	if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
+				       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM) &&
+	    EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM))
+		ext4_warning(sb, KERN_INFO "metadata_csum and uninit_bg are "
+			     "redundant flags; please run fsck.");
+
 	/* Check for a known checksum algorithm */
 	if (!ext4_verify_csum_type(sb, es)) {
 		ext4_msg(sb, KERN_ERR, "VFS: Found ext4 filesystem with "
@@ -4400,7 +4433,7 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 				struct ext4_group_desc *gdp =
 					ext4_get_group_desc(sb, g, NULL);
 
-				if (!ext4_group_desc_csum_verify(sbi, g, gdp)) {
+				if (!ext4_group_desc_csum_verify(sb, g, gdp)) {
 					ext4_msg(sb, KERN_ERR,
 	       "ext4_remount: Checksum for group %u failed (%u!=%u)",
 		g, le16_to_cpu(ext4_group_desc_csum(sbi, g, gdp)),