xfs: avoid repeated pointer dereferences

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

(This version drops an assertion that a pointer is non-null.)

Signed-off-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 13 insertions, 12 deletions

diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index a6cbc140c330..7b3375db6728 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -354,26 +354,27 @@ 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) {
+        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;
 }