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>

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index e10c9668e4fdcc9fd1d1a9db9e841eee4bc123de..0948d34cb84a5f24cb2221f54b1fe5a426f451eb 100644 (file)
--- 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;