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dm writecache: avoid unnecessary lookups in writecache_find_entry() 

This is a small optimization in writecache_find_entry().

If we go past the condition "if (unlikely(!node))", we can be certain that
there is no entry in the tree that has the block equal to the "block"
variable.

Consequently, we can return the next entry directly, we don't need to go
to the second part of the function that finds the entry with lowest or
highest seq number that matches the "block" variable.

Also, add some whitespace and cleanup needless braces.

Suggested-by: Huaisheng Ye <yehs1@lenovo.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mikulas Patocka 2019-04-26 09:59:24 -04:00 committed by Mike Snitzer
parent 08a8e80462
commit f8011d3344
1 changed files with 5 additions and 6 deletions
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11
drivers/md/dm-writecache.c
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@ -545,21 +545,20 @@ static struct wc_entry *writecache_find_entry(struct dm_writecache *wc,
e = container_of(node, struct wc_entry, rb_node);
if (read_original_sector(wc, e) == block)
break;
node = (read_original_sector(wc, e) >= block ?
e->rb_node.rb_left : e->rb_node.rb_right);
if (unlikely(!node)) {
if (!(flags & WFE_RETURN_FOLLOWING)) {
if (!(flags & WFE_RETURN_FOLLOWING))
return NULL;
}
if (read_original_sector(wc, e) >= block) {
break;
return e;
} else {
node = rb_next(&e->rb_node);
if (unlikely(!node)) {
if (unlikely(!node))
return NULL;
}
e = container_of(node, struct wc_entry, rb_node);
break;
return e;
}
}
}