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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>
This commit is contained in:
Alex Elder 2010-04-15 18:17:30 +00:00
parent 9db127edb5
commit e3bb2e30d5
1 changed files with 13 additions and 12 deletions
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25
fs/xfs/xfs_log_recover.c
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@ -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;
}