diff options
| -rw-r--r-- | fs/xfs/xfs_log_recover.c | 108 |
1 files changed, 77 insertions, 31 deletions
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c index c1337127d8fb..a5e2ca8f5cd6 100644 --- a/fs/xfs/xfs_log_recover.c +++ b/fs/xfs/xfs_log_recover.c @@ -1029,61 +1029,106 @@ out_error: } /* - * Check the log tail for torn writes. This is required when torn writes are - * detected at the head and the head had to be walked back to a previous record. - * The tail of the previous record must now be verified to ensure the torn - * writes didn't corrupt the previous tail. + * Calculate distance from head to tail (i.e., unused space in the log). + */ +static inline int +xlog_tail_distance( + struct xlog *log, + xfs_daddr_t head_blk, + xfs_daddr_t tail_blk) +{ + if (head_blk < tail_blk) + return tail_blk - head_blk; + + return tail_blk + (log->l_logBBsize - head_blk); +} + +/* + * Verify the log tail. This is particularly important when torn or incomplete + * writes have been detected near the front of the log and the head has been + * walked back accordingly. + * + * We also have to handle the case where the tail was pinned and the head + * blocked behind the tail right before a crash. If the tail had been pushed + * immediately prior to the crash and the subsequent checkpoint was only + * partially written, it's possible it overwrote the last referenced tail in the + * log with garbage. This is not a coherency problem because the tail must have + * been pushed before it can be overwritten, but appears as log corruption to + * recovery because we have no way to know the tail was updated if the + * subsequent checkpoint didn't write successfully. * - * Return an error if CRC verification fails as recovery cannot proceed. + * Therefore, CRC check the log from tail to head. If a failure occurs and the + * offending record is within max iclog bufs from the head, walk the tail + * forward and retry until a valid tail is found or corruption is detected out + * of the range of a possible overwrite. */ STATIC int xlog_verify_tail( struct xlog *log, xfs_daddr_t head_blk, - xfs_daddr_t tail_blk) + xfs_daddr_t *tail_blk, + int hsize) { struct xlog_rec_header *thead; struct xfs_buf *bp; xfs_daddr_t first_bad; - int count; int error = 0; bool wrapped; - xfs_daddr_t tmp_head; + xfs_daddr_t tmp_tail; + xfs_daddr_t orig_tail = *tail_blk; bp = xlog_get_bp(log, 1); if (!bp) return -ENOMEM; /* - * Seek XLOG_MAX_ICLOGS + 1 records past the current tail record to get - * a temporary head block that points after the last possible - * concurrently written record of the tail. + * Make sure the tail points to a record (returns positive count on + * success). */ - count = xlog_seek_logrec_hdr(log, head_blk, tail_blk, - XLOG_MAX_ICLOGS + 1, bp, &tmp_head, &thead, - &wrapped); - if (count < 0) { - error = count; + error = xlog_seek_logrec_hdr(log, head_blk, *tail_blk, 1, bp, + &tmp_tail, &thead, &wrapped); + if (error < 0) goto out; - } + if (*tail_blk != tmp_tail) + *tail_blk = tmp_tail; /* - * If the call above didn't find XLOG_MAX_ICLOGS + 1 records, we ran - * into the actual log head. tmp_head points to the start of the record - * so update it to the actual head block. + * Run a CRC check from the tail to the head. We can't just check + * MAX_ICLOGS records past the tail because the tail may point to stale + * blocks cleared during the search for the head/tail. These blocks are + * overwritten with zero-length records and thus record count is not a + * reliable indicator of the iclog state before a crash. */ - if (count < XLOG_MAX_ICLOGS + 1) - tmp_head = head_blk; - - /* - * We now have a tail and temporary head block that covers at least - * XLOG_MAX_ICLOGS records from the tail. We need to verify that these - * records were completely written. Run a CRC verification pass from - * tail to head and return the result. - */ - error = xlog_do_recovery_pass(log, tmp_head, tail_blk, + first_bad = 0; + error = xlog_do_recovery_pass(log, head_blk, *tail_blk, XLOG_RECOVER_CRCPASS, &first_bad); + while (error == -EFSBADCRC && first_bad) { + int tail_distance; + + /* + * Is corruption within range of the head? If so, retry from + * the next record. Otherwise return an error. + */ + tail_distance = xlog_tail_distance(log, head_blk, first_bad); + if (tail_distance > BTOBB(XLOG_MAX_ICLOGS * hsize)) + break; + /* skip to the next record; returns positive count on success */ + error = xlog_seek_logrec_hdr(log, head_blk, first_bad, 2, bp, + &tmp_tail, &thead, &wrapped); + if (error < 0) + goto out; + + *tail_blk = tmp_tail; + first_bad = 0; + error = xlog_do_recovery_pass(log, head_blk, *tail_blk, + XLOG_RECOVER_CRCPASS, &first_bad); + } + + if (!error && *tail_blk != orig_tail) + xfs_warn(log->l_mp, + "Tail block (0x%llx) overwrite detected. Updated to 0x%llx", + orig_tail, *tail_blk); out: xlog_put_bp(bp); return error; @@ -1187,7 +1232,8 @@ xlog_verify_head( if (error) return error; - return xlog_verify_tail(log, *head_blk, *tail_blk); + return xlog_verify_tail(log, *head_blk, tail_blk, + be32_to_cpu((*rhead)->h_size)); } /* |