1 files changed, 83 insertions, 35 deletions

diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 1be2590..423c36d 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -868,6 +868,79 @@ validate_head:
 }
 
 /*
+ * 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.
  *
  * This will be the block number of the last record to have its
@@ -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));