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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>
This commit is contained in:
Miao Xie 2012-10-18 08:18:01 +00:00 committed by Josef Bacik
parent de1ee92ac3
commit de6c4115a2
1 changed files with 10 additions and 20 deletions
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30
fs/btrfs/free-space-cache.c
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@ -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;