From 0584f718ed1f351fca5047a4b1ebba9b5ea41215 Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Fri, 2 Oct 2015 16:12:23 -0400 Subject: [PATCH] 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 Signed-off-by: Chris Mason --- fs/btrfs/free-space-cache.c | 28 +++++++++++++++------------- 1 file changed, 15 insertions(+), 13 deletions(-) diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c index e10c9668e4fd..0948d34cb84a 100644 --- a/fs/btrfs/free-space-cache.c +++ b/fs/btrfs/free-space-cache.c @@ -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; -- 2.20.1