Btrfs: fix unnecessary while loop when search the free space, cache

When we find a bitmap free space entry, we may check the previous extent
entry covers the offset or not. But if we find this entry is also a bitmap
entry, we will continue to check the previous entry of the current one by
a while loop. It is unnecessary because it is impossible that the extent
entry which is in front of a bitmap entry can cover the offset of the entry
after that bitmap entry.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 1027b85..557502c 100644 (file)
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -1250,18 +1250,13 @@ tree_search_offset(struct btrfs_free_space_ctl *ctl,
                         * if previous extent entry covers the offset,
                         * we should return it instead of the bitmap entry
                         */
-                       n = &entry->offset_index;
-                       while (1) {
-                               n = rb_prev(n);
-                               if (!n)
-                                       break;
+                       n = rb_prev(&entry->offset_index);
+                       if (n) {
                                prev = rb_entry(n, struct btrfs_free_space,
                                                offset_index);
-                               if (!prev->bitmap) {
-                                       if (prev->offset + prev->bytes > offset)
-                                               entry = prev;
-                                       break;
-                               }
+                               if (!prev->bitmap &&
+                                   prev->offset + prev->bytes > offset)
+                                       entry = prev;
                        }
                }
                return entry;
@@ -1287,18 +1282,13 @@ tree_search_offset(struct btrfs_free_space_ctl *ctl,
        }
 
        if (entry->bitmap) {
-               n = &entry->offset_index;
-               while (1) {
-                       n = rb_prev(n);
-                       if (!n)
-                               break;
+               n = rb_prev(&entry->offset_index);
+               if (n) {
                        prev = rb_entry(n, struct btrfs_free_space,
                                        offset_index);
-                       if (!prev->bitmap) {
-                               if (prev->offset + prev->bytes > offset)
-                                       return prev;
-                               break;
-                       }
+                       if (!prev->bitmap &&
+                           prev->offset + prev->bytes > offset)
+                               return prev;
                }
                if (entry->offset + BITS_PER_BITMAP * ctl->unit > offset)
                        return entry;