Miao Xie
2012-Oct-18 08:02 UTC
[PATCH] 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>
---
fs/btrfs/free-space-cache.c | 15 +++++----------
1 files changed, 5 insertions(+), 10 deletions(-)
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 1027b85..ac7e728 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;
--
1.7.6.5
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Miao Xie
2012-Oct-18 08:18 UTC
[PATCH V2] 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>
---
Changelog v1 -> v2:
- fix the same problem in the other place
---
fs/btrfs/free-space-cache.c | 30 ++++++++++--------------------
1 files changed, 10 insertions(+), 20 deletions(-)
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 1027b85..557502c 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;
--
1.7.6.5
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Liu Bo
2012-Oct-18 08:47 UTC
Re: [PATCH V2] Btrfs: fix unnecessary while loop when search the free space, cache
On 10/18/2012 04:18 PM, Miao Xie wrote:> 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. >Looks good to me. Reviewed-by: Liu Bo <bo.li.liu@oracle.com>> Signed-off-by: Miao Xie <miaox@cn.fujitsu.com> > --- > Changelog v1 -> v2: > - fix the same problem in the other place > --- > fs/btrfs/free-space-cache.c | 30 ++++++++++-------------------- > 1 files changed, 10 insertions(+), 20 deletions(-) > > diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c > index 1027b85..557502c 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; >-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html