[PATCHv2 9/10] xfs: a few more minor xfs_log_recover.c cleanups

Alex Elder
2010-04-09T22:29:47Z

Minor things that didn't seem to warrant their own individual
patches:
- In xlog_bread_noalign(), reorder assertions so the buffer pointer
is known to be non-null before attempting to dereference it.
- Add a more descriptive header comment for xlog_find_verify_cycle().
- Make a few additions to the comments in xlog_find_head(). Also
rearrange some expressions in a few spots to produce the same
result, but in a way that seems more clear what's being computed.

Signed-off-by: Alex Elder <aelder@sgi.com>

---
fs/xfs/xfs_log_recover.c | 83 ++++++++++++++++++++++++-----------------------
fs/xfs/xfs_log_recover.c | 25 +++++++++++++++----------
1 file changed, 15 insertions(+), 10 deletions(-)

Index: b/fs/xfs/xfs_log_recover.c
===================================================================
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -166,8 +166,8 @@ xlog_bread_noalign(
nbblks = round_up(nbblks, xlog_sectbb(log));

ASSERT(nbblks > 0);
- ASSERT(BBTOB(nbblks) <= XFS_BUF_SIZE(bp));
ASSERT(bp);
+ ASSERT(BBTOB(nbblks) <= XFS_BUF_SIZE(bp));

XFS_BUF_SET_ADDR(bp, log->l_logBBstart + blk_no);
XFS_BUF_READ(bp);
@@ -387,8 +387,11 @@ xlog_find_cycle_start(
* test. If the region is completely good, we end up returning the same
* last block number.
*
- * Set blkno to -1 if we encounter no errors. This is an invalid block number
- * since we don't ever expect logs to get this large.
+ * If we encounter a basic block containing stop_on_cycle_no as its
+ * cycle number, return that basic block offset in *new_blk. If no
+ * basic blocks in the range specified contain stop_on_cycle_no, set
+ * *new_blk to -1. This is an invalid block number since we don't
+ * ever expect logs to get this large.
*/
STATIC int
xlog_find_verify_cycle(
@@ -662,7 +665,7 @@ xlog_find_head(
* In this case we want to find the first block with cycle
* number matching last_half_cycle. We expect the log to be
* some variation on
- * x + 1 ... | x ...
+ * x + 1 ... | x ... | x
* The first block with cycle number x (last_half_cycle) will
* be where the new head belongs. First we do a binary search
* for the first occurrence of last_half_cycle. The binary
@@ -672,11 +675,13 @@ xlog_find_head(
* the log, then we look for occurrences of last_half_cycle - 1
* at the end of the log. The cases we're looking for look
* like
- * x + 1 ... | x | x + 1 | x ...
- * ^ binary search stopped here
+ * v binary search stopped here
+ * x + 1 ... | x | x + 1 | x ... | x
+ * ^ but we want to locate this spot
* or
- * x + 1 ... | x ... | x - 1 | x
* <---------> less than scan distance
+ * x + 1 ... | x ... | x - 1 | x
+ * ^ we want to locate this spot
*/
stop_on_cycle = last_half_cycle;
if ((error = xlog_find_cycle_start(log, bp, first_blk,
@@ -732,9 +737,9 @@ xlog_find_head(
* certainly not the head of the log. By searching for
* last_half_cycle-1 we accomplish that.
*/
- start_blk = log_bbnum - num_scan_bblks + head_blk;
ASSERT(head_blk <= INT_MAX &&
- (xfs_daddr_t) num_scan_bblks - head_blk >= 0);
+ (xfs_daddr_t) num_scan_bblks >= head_blk);
+ start_blk = log_bbnum - (num_scan_bblks - head_blk);
if ((error = xlog_find_verify_cycle(log, start_blk,
num_scan_bblks - (int)head_blk,
(stop_on_cycle - 1), &new_blk)))
@@ -781,7 +786,7 @@ fine_tune:
if ((error = xlog_find_verify_log_record(log, start_blk,
&head_blk, 0)) == -1) {
/* We hit the beginning of the log during our search */
- start_blk = log_bbnum - num_scan_bblks + head_blk;
+ start_blk = log_bbnum - (num_scan_bblks - head_blk);
new_blk = log_bbnum;
ASSERT(start_blk <= INT_MAX &&