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Commit 0584f718 authored by Josef Bacik's avatar Josef Bacik Committed by Chris Mason
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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: default avatarJosef Bacik <jbacik@fb.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent cef40483

fs/btrfs/free-space-cache.c

+15 −13
Original line number Diff line number Diff line
@@ -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 @@ static noinline int remove_from_bitmap(struct btrfs_free_space_ctl *ctl, 
	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 @@ static noinline int remove_from_bitmap(struct btrfs_free_space_ctl *ctl, 
		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 @@ int test_add_free_space_entry(struct btrfs_block_group_cache *cache, 


	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 @@ int test_check_exists(struct btrfs_block_group_cache *cache, 


		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;