ext4: Add the journal checksum feature
The journal checksum feature adds two new flags i.e
JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT and JBD2_FEATURE_COMPAT_CHECKSUM.
JBD2_FEATURE_CHECKSUM flag indicates that the commit block contains the
checksum for the blocks described by the descriptor blocks.
Due to checksums, writing of the commit record no longer needs to be
synchronous. Now commit record can be sent to disk without waiting for
descriptor blocks to be written to disk. This behavior is controlled
using JBD2_FEATURE_ASYNC_COMMIT flag. Older kernels/e2fsck should not be
able to recover the journal with _ASYNC_COMMIT hence it is made
incompat.
The commit header has been extended to hold the checksum along with the
type of the checksum.
For recovery in pass scan checksums are verified to ensure the sanity
and completeness(in case of _ASYNC_COMMIT) of every transaction.
Signed-off-by: Andreas Dilger <adilger@clusterfs.com>
Signed-off-by: Girish Shilamkar <girish@clusterfs.com>
Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 6856400..98a2bc5 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -149,6 +149,28 @@
__be32 h_sequence;
} journal_header_t;
+/*
+ * Checksum types.
+ */
+#define JBD2_CRC32_CHKSUM 1
+#define JBD2_MD5_CHKSUM 2
+#define JBD2_SHA1_CHKSUM 3
+
+#define JBD2_CRC32_CHKSUM_SIZE 4
+
+#define JBD2_CHECKSUM_BYTES (32 / sizeof(u32))
+/*
+ * Commit block header for storing transactional checksums:
+ */
+struct commit_header {
+ __be32 h_magic;
+ __be32 h_blocktype;
+ __be32 h_sequence;
+ unsigned char h_chksum_type;
+ unsigned char h_chksum_size;
+ unsigned char h_padding[2];
+ __be32 h_chksum[JBD2_CHECKSUM_BYTES];
+};
/*
* The block tag: used to describe a single buffer in the journal.
@@ -242,14 +264,18 @@
((j)->j_format_version >= 2 && \
((j)->j_superblock->s_feature_incompat & cpu_to_be32((mask))))
-#define JBD2_FEATURE_INCOMPAT_REVOKE 0x00000001
-#define JBD2_FEATURE_INCOMPAT_64BIT 0x00000002
+#define JBD2_FEATURE_COMPAT_CHECKSUM 0x00000001
+
+#define JBD2_FEATURE_INCOMPAT_REVOKE 0x00000001
+#define JBD2_FEATURE_INCOMPAT_64BIT 0x00000002
+#define JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT 0x00000004
/* Features known to this kernel version: */
-#define JBD2_KNOWN_COMPAT_FEATURES 0
+#define JBD2_KNOWN_COMPAT_FEATURES JBD2_FEATURE_COMPAT_CHECKSUM
#define JBD2_KNOWN_ROCOMPAT_FEATURES 0
#define JBD2_KNOWN_INCOMPAT_FEATURES (JBD2_FEATURE_INCOMPAT_REVOKE | \
- JBD2_FEATURE_INCOMPAT_64BIT)
+ JBD2_FEATURE_INCOMPAT_64BIT | \
+ JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)
#ifdef __KERNEL__
@@ -997,6 +1023,8 @@
(journal_t *, unsigned long, unsigned long, unsigned long);
extern int jbd2_journal_set_features
(journal_t *, unsigned long, unsigned long, unsigned long);
+extern void jbd2_journal_clear_features
+ (journal_t *, unsigned long, unsigned long, unsigned long);
extern int jbd2_journal_create (journal_t *);
extern int jbd2_journal_load (journal_t *journal);
extern void jbd2_journal_destroy (journal_t *);