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Subject[PATCH v2 2/4] dm writecache: add unlikely for returned value of rb_next/prev
Date
From: Huaisheng Ye <yehs1@lenovo.com>

In functions writecache_discard() and writecache_find_entry() there is a
high probablity that the pointer of structure rb_node won't equal NULL.
Add unlikely for the pointer node NULL.

Signed-off-by: Huaisheng Ye <yehs1@lenovo.com>
Acked-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
drivers/md/dm-writecache.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index 5b4d1c1..cfbbfbc 100644
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -571,7 +571,7 @@ static struct wc_entry *writecache_find_entry(struct dm_writecache *wc,
node = rb_prev(&e->rb_node);
else
node = rb_next(&e->rb_node);
- if (!node)
+ if (unlikely(!node))
return e;
e2 = container_of(node, struct wc_entry, rb_node);
if (read_original_sector(wc, e2) != block)
@@ -804,7 +804,7 @@ static void writecache_discard(struct dm_writecache *wc, sector_t start, sector_
writecache_free_entry(wc, e);
}

- if (!node)
+ if (unlikely(!node))
break;

e = container_of(node, struct wc_entry, rb_node);
--
1.8.3.1

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