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Btrfs: don't do extra bitmap search in one bit case 

When we make ctl->unit allocations from a bitmap there is no point in searching
for the next 0 in the bitmap.  If we've found a bit we're done and can just exit
the loop.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
This commit is contained in:
Josef Bacik 2015-10-02 16:12:23 -04:00 committed by Chris Mason
parent cef4048370
commit 0584f718ed
1 changed files with 15 additions and 13 deletions
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28
fs/btrfs/free-space-cache.c
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@ -1730,7 +1730,7 @@ static void bitmap_set_bits(struct btrfs_free_space_ctl *ctl,
*/
static int search_bitmap(struct btrfs_free_space_ctl *ctl,
struct btrfs_free_space *bitmap_info, u64 *offset,
u64 *bytes)
u64 *bytes, bool for_alloc)
{
unsigned long found_bits = 0;
unsigned long max_bits = 0;
@ -1742,7 +1742,8 @@ static int search_bitmap(struct btrfs_free_space_ctl *ctl,
* Skip searching the bitmap if we don't have a contiguous section that
* is large enough for this allocation.
*/
if (bitmap_info->max_extent_size &&
if (for_alloc &&
bitmap_info->max_extent_size &&
bitmap_info->max_extent_size < *bytes) {
*bytes = bitmap_info->max_extent_size;
return -1;
@ -1753,6 +1754,10 @@ static int search_bitmap(struct btrfs_free_space_ctl *ctl,
bits = bytes_to_bits(*bytes, ctl->unit);
for_each_set_bit_from(i, bitmap_info->bitmap, BITS_PER_BITMAP) {
if (for_alloc && bits == 1) {
found_bits = 1;
break;
}
next_zero = find_next_zero_bit(bitmap_info->bitmap,
BITS_PER_BITMAP, i);
extent_bits = next_zero - i;
@ -1824,7 +1829,7 @@ find_free_space(struct btrfs_free_space_ctl *ctl, u64 *offset, u64 *bytes,
if (entry->bitmap) {
u64 size = *bytes;
ret = search_bitmap(ctl, entry, &tmp, &size);
ret = search_bitmap(ctl, entry, &tmp, &size, true);
if (!ret) {
*offset = tmp;
*bytes = size;
@ -1885,7 +1890,8 @@ again:
search_start = *offset;
search_bytes = ctl->unit;
search_bytes = min(search_bytes, end - search_start + 1);
ret = search_bitmap(ctl, bitmap_info, &search_start, &search_bytes);
ret = search_bitmap(ctl, bitmap_info, &search_start, &search_bytes,
false);
if (ret < 0 || search_start != *offset)
return -EINVAL;
@ -1930,7 +1936,7 @@ again:
search_start = *offset;
search_bytes = ctl->unit;
ret = search_bitmap(ctl, bitmap_info, &search_start,
&search_bytes);
&search_bytes, false);
if (ret < 0 || search_start != *offset)
return -EAGAIN;
@ -2685,7 +2691,7 @@ static u64 btrfs_alloc_from_bitmap(struct btrfs_block_group_cache *block_group,
search_start = min_start;
search_bytes = bytes;
err = search_bitmap(ctl, entry, &search_start, &search_bytes);
err = search_bitmap(ctl, entry, &search_start, &search_bytes, true);
if (err) {
if (search_bytes > *max_extent_size)
*max_extent_size = search_bytes;
@ -3262,7 +3268,7 @@ static int trim_bitmaps(struct btrfs_block_group_cache *block_group,
}
bytes = minlen;
ret2 = search_bitmap(ctl, entry, &start, &bytes);
ret2 = search_bitmap(ctl, entry, &start, &bytes, false);
if (ret2 || start >= end) {
spin_unlock(&ctl->tree_lock);
mutex_unlock(&ctl->cache_writeout_mutex);
@ -3415,7 +3421,7 @@ u64 btrfs_find_ino_for_alloc(struct btrfs_root *fs_root)
u64 count = 1;
int ret;
ret = search_bitmap(ctl, entry, &offset, &count);
ret = search_bitmap(ctl, entry, &offset, &count, true);
/* Logic error; Should be empty if it can't find anything */
ASSERT(!ret);
@ -3600,10 +3606,6 @@ again:
bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes);
/* We used the newly allocated info, set the max_extent_size to bytes */
if (!info)
bitmap_info->max_extent_size = bytes_added;
bytes -= bytes_added;
offset += bytes_added;
spin_unlock(&ctl->tree_lock);
@ -3647,7 +3649,7 @@ have_info:
bit_off = offset;
bit_bytes = ctl->unit;
ret = search_bitmap(ctl, info, &bit_off, &bit_bytes);
ret = search_bitmap(ctl, info, &bit_off, &bit_bytes, false);
if (!ret) {
if (bit_off == offset) {
ret = 1;