[PATCH 19/22] jbd2: Checksum revocation blocks

["Darrick J. Wong" <djwong@us.ibm.com>]

Compute and verify revoke blocks inside the journal.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
---
 fs/jbd2/recovery.c   |   35 +++++++++++++++++++++++++++++++++--
 fs/jbd2/revoke.c     |   27 ++++++++++++++++++++++++++-
 include/linux/jbd2.h |    4 ++++
 3 files changed, 63 insertions(+), 3 deletions(-)


diff --git a/fs/jbd2/recovery.c b/fs/jbd2/recovery.c
index da6d7ba..63885e0 100644
--- a/fs/jbd2/recovery.c
+++ b/fs/jbd2/recovery.c
@@ -662,8 +662,17 @@ static int do_one_pass(journal_t *journal,
 			err = scan_revoke_records(journal, bh,
 						  next_commit_ID, info);
 			brelse(bh);
-			if (err)
-				goto failed;
+			if (err) {
+				if (err != -EINVAL)
+					goto failed;
+				/*
+				 * Ignoring corrupt revoke blocks is safe
+				 * because at worst it results in unnecessary
+				 * writes during recovery.
+				 */
+				jbd_debug(3, "Skipping corrupt revoke "
+					  "block.\n");
+			}
 			continue;
 
 		default:
@@ -703,6 +712,25 @@ static int do_one_pass(journal_t *journal,
 	return err;
 }
 
+static int jbd2_revoke_block_csum_verify(journal_t *j,
+					 void *buf)
+{
+	struct jbd2_journal_revoke_tail *tail;
+	__u32 provided, calculated;
+
+	if (!JBD2_HAS_INCOMPAT_FEATURE(j, JBD2_FEATURE_INCOMPAT_CSUM_V2))
+		return 1;
+
+	tail = (struct jbd2_journal_revoke_tail *)(buf + j->j_blocksize -
+			sizeof(struct jbd2_journal_revoke_tail));
+	provided = tail->r_checksum;
+	tail->r_checksum = 0;
+	calculated = jbd2_chksum(j, j->j_uuid_csum, buf, j->j_blocksize);
+	tail->r_checksum = provided;
+
+	provided = be32_to_cpu(provided);
+	return provided == calculated;
+}
 
 /* Scan a revoke record, marking all blocks mentioned as revoked. */
 
@@ -717,6 +745,9 @@ static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
 	offset = sizeof(jbd2_journal_revoke_header_t);
 	max = be32_to_cpu(header->r_count);
 
+	if (!jbd2_revoke_block_csum_verify(journal, header))
+		return -EINVAL;
+
 	if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_64BIT))
 		record_len = 8;
 
diff --git a/fs/jbd2/revoke.c b/fs/jbd2/revoke.c
index 69fd935..3b6aaab 100644
--- a/fs/jbd2/revoke.c
+++ b/fs/jbd2/revoke.c
@@ -548,6 +548,7 @@ static void write_one_revoke_record(journal_t *journal,
 				    struct jbd2_revoke_record_s *record,
 				    int write_op)
 {
+	int csum_size = 0;
 	struct journal_head *descriptor;
 	int offset;
 	journal_header_t *header;
@@ -562,9 +563,13 @@ static void write_one_revoke_record(journal_t *journal,
 	descriptor = *descriptorp;
 	offset = *offsetp;
 
+	/* Do we need to leave space at the end for a checksum? */
+	if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_CSUM_V2))
+		csum_size = sizeof(struct jbd2_journal_revoke_tail);
+
 	/* Make sure we have a descriptor with space left for the record */
 	if (descriptor) {
-		if (offset == journal->j_blocksize) {
+		if (offset >= journal->j_blocksize - csum_size) {
 			flush_descriptor(journal, descriptor, offset, write_op);
 			descriptor = NULL;
 		}
@@ -601,6 +606,24 @@ static void write_one_revoke_record(journal_t *journal,
 	*offsetp = offset;
 }
 
+static void jbd2_revoke_csum_set(journal_t *j,
+				 struct journal_head *descriptor)
+{
+	struct jbd2_journal_revoke_tail *tail;
+	__u32 csum;
+
+	if (!JBD2_HAS_INCOMPAT_FEATURE(j, JBD2_FEATURE_INCOMPAT_CSUM_V2))
+		return;
+
+	tail = (struct jbd2_journal_revoke_tail *)
+			(jh2bh(descriptor)->b_data + j->j_blocksize -
+			sizeof(struct jbd2_journal_revoke_tail));
+	tail->r_checksum = 0;
+	csum = jbd2_chksum(j, j->j_uuid_csum, jh2bh(descriptor)->b_data,
+			   j->j_blocksize);
+	tail->r_checksum = cpu_to_be32(csum);
+}
+
 /*
  * Flush a revoke descriptor out to the journal.  If we are aborting,
  * this is a noop; otherwise we are generating a buffer which needs to
@@ -622,6 +645,8 @@ static void flush_descriptor(journal_t *journal,
 
 	header = (jbd2_journal_revoke_header_t *) jh2bh(descriptor)->b_data;
 	header->r_count = cpu_to_be32(offset);
+	jbd2_revoke_csum_set(journal, descriptor);
+
 	set_buffer_jwrite(bh);
 	BUFFER_TRACE(bh, "write");
 	set_buffer_dirty(bh);
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 3bf4fe3..c8e1abe 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -194,6 +194,10 @@ typedef struct jbd2_journal_revoke_header_s
 	__be32		 r_count;	/* Count of bytes used in the block */
 } jbd2_journal_revoke_header_t;
 
+/* Tail of revoke block, for checksumming */
+struct jbd2_journal_revoke_tail {
+	__be32		r_checksum;	/* crc32c(uuid+revoke_block) */
+};
 
 /* Definitions for the journal tag flags word: */
 #define JBD2_FLAG_ESCAPE		1	/* on-disk block is escaped */