2009-08-16 19:24:32

by Eric Sandeen

Subject: [PATCH] ext4: simplify some logic in ext4_mb_normalize_request

While reading through some of the mballoc code it seems that a couple
spots in the size normalization function could be streamlined.

The test for non-overlapping PAs can be or'd for the start & end
conditions, and the tests for adjacent PAs can be else-if'd -
it's essentially independently testing:

if (A + B <= C)
...
if (A > C)
...

These cannot both be true so it seems like the else-if might
be slightly more efficient and/or informative.

Signed-off-by: Eric Sandeen <[email protected]>
---

mballoc.c | 13 ++++---------
1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 2741b11..992ec20 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3171,23 +3171,18 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
BUG_ON(!(ac->ac_o_ex.fe_logical >= pa_end ||
ac->ac_o_ex.fe_logical < pa->pa_lstart));

- /* skip PA normalized request doesn't overlap with */
- if (pa->pa_lstart >= end) {
- spin_unlock(&pa->pa_lock);
- continue;
- }
- if (pa_end <= start) {
+ /* skip PAs this normalized request doesn't overlap with */
+ if (pa->pa_lstart >= end || pa_end <= start) {
spin_unlock(&pa->pa_lock);
continue;
}
BUG_ON(pa->pa_lstart <= start && pa_end >= end);

+ /* adjust start or end to be adjacent to this pa */
if (pa_end <= ac->ac_o_ex.fe_logical) {
BUG_ON(pa_end < start);
start = pa_end;
- }

2009-08-18 04:31:12

by Theodore Ts'o

Subject: Re: [PATCH] ext4: simplify some logic in ext4_mb_normalize_request

Thanks, added to the ext4 patch queue.

- Ted