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>

1 files changed, 10 insertions, 20 deletions

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 1027b854b90c..557502ca1a2a 100644
--- 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;