[PATCHv2 8/10] xfs: avoid repeated pointer dereferences

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

In xlog_find_cycle_start() use a local variable for some repeated
operations rather than constantly updating the memory location
whose address is passed in.

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

---
fs/xfs/xfs_log_recover.c | 83 ++++++++++++++++++++++++-----------------------
fs/xfs/xfs_log_recover.c | 26 ++++++++++++++------------
1 file changed, 14 insertions(+), 12 deletions(-)

Index: b/fs/xfs/xfs_log_recover.c
===================================================================
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -354,26 +354,28 @@ xlog_find_cycle_start(
{
xfs_caddr_t offset;
xfs_daddr_t mid_blk;
+ xfs_daddr_t end_blk;
uint mid_cycle;
int error;

- mid_blk = BLK_AVG(first_blk, *last_blk);
- while (mid_blk != first_blk && mid_blk != *last_blk) {
+ ASSERT(last_blk != NULL);
+ end_blk = *last_blk;
+ mid_blk = BLK_AVG(first_blk, end_blk);
+ while (mid_blk != first_blk && mid_blk != end_blk) {
error = xlog_bread(log, mid_blk, 1, bp, &offset);
if (error)
return error;
mid_cycle = xlog_get_cycle(offset);
- if (mid_cycle == cycle) {
- *last_blk = mid_blk;
- /* last_half_cycle == mid_cycle */
- } else {
- first_blk = mid_blk;
- /* first_half_cycle == mid_cycle */
- }
- mid_blk = BLK_AVG(first_blk, *last_blk);
+ if (mid_cycle == cycle)
+ end_blk = mid_blk; /* last_half_cycle == mid_cycle */
+ else
+ first_blk = mid_blk; /* first_half_cycle == mid_cycle */
+ mid_blk = BLK_AVG(first_blk, end_blk);
}
- ASSERT((mid_blk == first_blk && mid_blk+1 == *last_blk) ||
- (mid_blk == *last_blk && mid_blk-1 == first_blk));
+ ASSERT((mid_blk == first_blk && mid_blk+1 == end_blk) ||
+ (mid_blk == end_blk && mid_blk-1 == first_blk));
+
+ *last_blk = end_blk;

return 0;
}