1 files changed, 143 insertions, 8 deletions

diff --git a/fs/jbd2/recovery.c b/fs/jbd2/recovery.c
index d0ce627539e..921680663fa 100644
--- a/fs/jbd2/recovery.c
+++ b/fs/jbd2/recovery.c
@@ -21,6 +21,7 @@
 #include <linux/jbd2.h>
 #include <linux/errno.h>
 #include <linux/slab.h>
+#include <linux/crc32.h>
 #endif
 
 /*
@@ -316,6 +317,37 @@ static inline unsigned long long read_tag_block(int tag_bytes, journal_block_tag
         return block;
 }
 
+/*
+ * calc_chksums calculates the checksums for the blocks described in the
+ * descriptor block.
+ */
+static int calc_chksums(journal_t *journal, struct buffer_head *bh,
+                        unsigned long *next_log_block, __u32 *crc32_sum)
+{
+        int i, num_blks, err;
+        unsigned long io_block;
+        struct buffer_head *obh;
+
+        num_blks = count_tags(journal, bh);
+        /* Calculate checksum of the descriptor block. */
+        *crc32_sum = crc32_be(*crc32_sum, (void *)bh->b_data, bh->b_size);
+
+        for (i = 0; i < num_blks; i++) {
+                io_block = (*next_log_block)++;
+                wrap(journal, *next_log_block);
+                err = jread(&obh, journal, io_block);
+                if (err) {
+                        printk(KERN_ERR "JBD: IO error %d recovering block "
+                                "%lu in log\n", err, io_block);
+                        return 1;
+                } else {
+                        *crc32_sum = crc32_be(*crc32_sum, (void *)obh->b_data,
+                                     obh->b_size);
+                }
+        }
+        return 0;
+}
+
 static int do_one_pass(journal_t *journal,
                         struct recovery_info *info, enum passtype pass)
 {
@@ -328,6 +360,7 @@ static int do_one_pass(journal_t *journal,
         unsigned int            sequence;
         int                     blocktype;
         int                     tag_bytes = journal_tag_bytes(journal);
+        __u32                   crc32_sum = ~0; /* Transactional Checksums */
 
         /* Precompute the maximum metadata descriptors in a descriptor block */
         int                     MAX_BLOCKS_PER_DESC;
@@ -419,12 +452,26 @@ static int do_one_pass(journal_t *journal,
                 switch(blocktype) {
                 case JBD2_DESCRIPTOR_BLOCK:
                         /* If it is a valid descriptor block, replay it
-                         * in pass REPLAY; otherwise, just skip over the
-                         * blocks it describes. */
+                         * in pass REPLAY; if journal_checksums enabled, then
+                         * calculate checksums in PASS_SCAN, otherwise,
+                         * just skip over the blocks it describes. */
                         if (pass != PASS_REPLAY) {
+                                if (pass == PASS_SCAN &&
+                                    JBD2_HAS_COMPAT_FEATURE(journal,
+                                            JBD2_FEATURE_COMPAT_CHECKSUM) &&
+                                    !info->end_transaction) {
+                                        if (calc_chksums(journal, bh,
+                                                        &next_log_block,
+                                                        &crc32_sum)) {
+                                                put_bh(bh);
+                                                break;
+                                        }
+                                        put_bh(bh);
+                                        continue;
+                                }
                                 next_log_block += count_tags(journal, bh);
                                 wrap(journal, next_log_block);
-                                brelse(bh);
+                                put_bh(bh);
                                 continue;
                         }
 
@@ -516,9 +563,96 @@ static int do_one_pass(journal_t *journal,
                         continue;
 
                 case JBD2_COMMIT_BLOCK:
-                        /* Found an expected commit block: not much to
-                         * do other than move on to the next sequence
+                        /*     How to differentiate between interrupted commit
+                         *               and journal corruption ?
+                         *
+                         * {nth transaction}
+                         *        Checksum Verification Failed
+                         *                       |
+                         *               ____________________
+                         *              |                    |
+                         *      async_commit             sync_commit
+                         *              |                    |
+                         *              | GO TO NEXT    "Journal Corruption"
+                         *              | TRANSACTION
+                         *              |
+                         * {(n+1)th transanction}
+                         *              |
+                         *       _______|______________
+                         *      |                     |
+                         * Commit block found   Commit block not found
+                         *      |                     |
+                         * "Journal Corruption"       |
+                         *               _____________|_________
+                         *              |                       |
+                         *      nth trans corrupt       OR   nth trans
+                         *      and (n+1)th interrupted     interrupted
+                         *      before commit block
+                         *      could reach the disk.
+                         *      (Cannot find the difference in above
+                         *       mentioned conditions. Hence assume
+                         *       "Interrupted Commit".)
+                         */
+
+                        /* Found an expected commit block: if checksums
+                         * are present verify them in PASS_SCAN; else not
+                         * much to do other than move on to the next sequence
                          * number. */
+                        if (pass == PASS_SCAN &&
+                            JBD2_HAS_COMPAT_FEATURE(journal,
+                                    JBD2_FEATURE_COMPAT_CHECKSUM)) {
+                                int chksum_err, chksum_seen;
+                                struct commit_header *cbh =
+                                        (struct commit_header *)bh->b_data;
+                                unsigned found_chksum =
+                                        be32_to_cpu(cbh->h_chksum[0]);
+
+                                chksum_err = chksum_seen = 0;
+
+                                if (info->end_transaction) {
+                                        printk(KERN_ERR "JBD: Transaction %u "
+                                                "found to be corrupt.\n",
+                                                next_commit_ID - 1);
+                                        brelse(bh);
+                                        break;
+                                }
+
+                                if (crc32_sum == found_chksum &&
+                                    cbh->h_chksum_type == JBD2_CRC32_CHKSUM &&
+                                    cbh->h_chksum_size ==
+                                                JBD2_CRC32_CHKSUM_SIZE)
+                                       chksum_seen = 1;
+                                else if (!(cbh->h_chksum_type == 0 &&
+                                             cbh->h_chksum_size == 0 &&
+                                             found_chksum == 0 &&
+                                             !chksum_seen))
+                                /*
+                                 * If fs is mounted using an old kernel and then
+                                 * kernel with journal_chksum is used then we
+                                 * get a situation where the journal flag has
+                                 * checksum flag set but checksums are not
+                                 * present i.e chksum = 0, in the individual
+                                 * commit blocks.
+                                 * Hence to avoid checksum failures, in this
+                                 * situation, this extra check is added.
+                                 */
+                                                chksum_err = 1;
+
+                                if (chksum_err) {
+                                        info->end_transaction = next_commit_ID;
+
+                                        if (!JBD2_HAS_COMPAT_FEATURE(journal,
+                                           JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)){
+                                                printk(KERN_ERR
+                                                       "JBD: Transaction %u "
+                                                       "found to be corrupt.\n",
+                                                       next_commit_ID);
+                                                brelse(bh);
+                                                break;
+                                        }
+                                }
+                                crc32_sum = ~0;
+                        }
                         brelse(bh);
                         next_commit_ID++;
                         continue;
@@ -554,9 +688,10 @@ static int do_one_pass(journal_t *journal,
          * transaction marks the end of the valid log.
          */
 
-        if (pass == PASS_SCAN)
-                info->end_transaction = next_commit_ID;
-        else {
+        if (pass == PASS_SCAN) {
+                if (!info->end_transaction)
+                        info->end_transaction = next_commit_ID;
+        } else {
                 /* It's really bad news if different passes end up at
                  * different places (but possible due to IO errors). */
                 if (info->end_transaction != next_commit_ID) {