From: Brian Foster Date: Mon, 4 Jan 2016 04:55:10 +0000 (+1100) Subject: xfs: refactor log record start detection into a new helper X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=eed6b462fb2a2661a416c227be6498b0ea2a7aab;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git xfs: refactor log record start detection into a new helper As part of the head/tail discovery process, log recovery locates the head block and then reverse seeks to find the start of the last active record in the log. This is non-trivial as the record itself could have wrapped around the end of the physical log. Log recovery torn write detection potentially needs to walk further behind the last record in the log, as multiple log I/Os can be in-flight at one time during a crash event. Therefore, refactor the reverse log record header search mechanism into a new helper that supports the ability to seek past an arbitrary number of log records (or until the tail is hit). Update the head/tail search mechanism to call the new helper, but otherwise there is no change in log recovery behavior. Signed-off-by: Brian Foster Reviewed-by: Dave Chinner Signed-off-by: Dave Chinner --- diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c index 1be259044096..423c36dbcdea 100644 --- a/fs/xfs/xfs_log_recover.c +++ b/fs/xfs/xfs_log_recover.c @@ -867,6 +867,79 @@ validate_head: return error; } +/* + * Seek backwards in the log for log record headers. + * + * Given a starting log block, walk backwards until we find the provided number + * of records or hit the provided tail block. The return value is the number of + * records encountered or a negative error code. The log block and buffer + * pointer of the last record seen are returned in rblk and rhead respectively. + */ +STATIC int +xlog_rseek_logrec_hdr( + struct xlog *log, + xfs_daddr_t head_blk, + xfs_daddr_t tail_blk, + int count, + struct xfs_buf *bp, + xfs_daddr_t *rblk, + struct xlog_rec_header **rhead, + bool *wrapped) +{ + int i; + int error; + int found = 0; + char *offset = NULL; + xfs_daddr_t end_blk; + + *wrapped = false; + + /* + * Walk backwards from the head block until we hit the tail or the first + * block in the log. + */ + end_blk = head_blk > tail_blk ? tail_blk : 0; + for (i = (int) head_blk - 1; i >= end_blk; i--) { + error = xlog_bread(log, i, 1, bp, &offset); + if (error) + goto out_error; + + if (*(__be32 *) offset == cpu_to_be32(XLOG_HEADER_MAGIC_NUM)) { + *rblk = i; + *rhead = (struct xlog_rec_header *) offset; + if (++found == count) + break; + } + } + + /* + * If we haven't hit the tail block or the log record header count, + * start looking again from the end of the physical log. Note that + * callers can pass head == tail if the tail is not yet known. + */ + if (tail_blk >= head_blk && found != count) { + for (i = log->l_logBBsize - 1; i >= (int) tail_blk; i--) { + error = xlog_bread(log, i, 1, bp, &offset); + if (error) + goto out_error; + + if (*(__be32 *)offset == + cpu_to_be32(XLOG_HEADER_MAGIC_NUM)) { + *wrapped = true; + *rblk = i; + *rhead = (struct xlog_rec_header *) offset; + if (++found == count) + break; + } + } + } + + return found; + +out_error: + return error; +} + /* * Find the sync block number or the tail of the log. * @@ -898,8 +971,7 @@ xlog_find_tail( xfs_daddr_t after_umount_blk; xfs_lsn_t tail_lsn; int hblks; - - found = 0; + bool wrapped = false; /* * Find previous log record @@ -923,37 +995,16 @@ xlog_find_tail( } /* - * Search backwards looking for log record header block + * Search backwards through the log looking for the log record header + * block. This wraps all the way back around to the head so something is + * seriously wrong if we can't find it. */ ASSERT(*head_blk < INT_MAX); - for (i = (int)(*head_blk) - 1; i >= 0; i--) { - error = xlog_bread(log, i, 1, bp, &offset); - if (error) - goto done; - - if (*(__be32 *)offset == cpu_to_be32(XLOG_HEADER_MAGIC_NUM)) { - found = 1; - break; - } - } - /* - * If we haven't found the log record header block, start looking - * again from the end of the physical log. XXXmiken: There should be - * a check here to make sure we didn't search more than N blocks in - * the previous code. - */ - if (!found) { - for (i = log->l_logBBsize - 1; i >= (int)(*head_blk); i--) { - error = xlog_bread(log, i, 1, bp, &offset); - if (error) - goto done; - - if (*(__be32 *)offset == - cpu_to_be32(XLOG_HEADER_MAGIC_NUM)) { - found = 2; - break; - } - } + found = xlog_rseek_logrec_hdr(log, *head_blk, *head_blk, 1, bp, &i, + &rhead, &wrapped); + if (found < 0) { + error = found; + goto done; } if (!found) { xfs_warn(log->l_mp, "%s: couldn't find sync record", __func__); @@ -961,9 +1012,6 @@ xlog_find_tail( ASSERT(0); return -EIO; } - - /* find blk_no of tail of log */ - rhead = (xlog_rec_header_t *)offset; *tail_blk = BLOCK_LSN(be64_to_cpu(rhead->h_tail_lsn)); /* @@ -979,7 +1027,7 @@ xlog_find_tail( log->l_prev_block = i; log->l_curr_block = (int)*head_blk; log->l_curr_cycle = be32_to_cpu(rhead->h_cycle); - if (found == 2) + if (wrapped) log->l_curr_cycle++; atomic64_set(&log->l_tail_lsn, be64_to_cpu(rhead->h_tail_lsn)); atomic64_set(&log->l_last_sync_lsn, be64_to_cpu(rhead->h_lsn));