ext4: reuse order and buddy in mb_mark_used when buddy split

After each buddy split, mb_mark_used will search the proper order
for the block which may consume some loop in mb_find_order_for_block.
In fact, we can reuse the order and buddy generated by the buddy split.

Reviewed by: lei.rao@intel.com
Signed-off-by: hanjinke <hanjinke.666@bytedance.com>
Link: https://lore.kernel.org/r/20220606155305.74146-1-hanjinke.666@bytedance.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 9e06334771a394fb0cb60615a22af507b19c25d9..b02f71f07289d199e75204040e0b353017fa7698 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1933,6 +1933,7 @@ static int mb_mark_used(struct ext4_buddy *e4b, struct ext4_free_extent *ex)
        unsigned ret = 0;
        int len0 = len;
        void *buddy;
+       bool split = false;
 
        BUG_ON(start + len > (e4b->bd_sb->s_blocksize << 3));
        BUG_ON(e4b->bd_group != ex->fe_group);
@@ -1957,12 +1958,16 @@ static int mb_mark_used(struct ext4_buddy *e4b, struct ext4_free_extent *ex)
 
        /* let's maintain buddy itself */
        while (len) {
-               ord = mb_find_order_for_block(e4b, start);
+               if (!split)
+                       ord = mb_find_order_for_block(e4b, start);
 
                if (((start >> ord) << ord) == start && len >= (1 << ord)) {
                        /* the whole chunk may be allocated at once! */
                        mlen = 1 << ord;
-                       buddy = mb_find_buddy(e4b, ord, &max);
+                       if (!split)
+                               buddy = mb_find_buddy(e4b, ord, &max);
+                       else
+                               split = false;
                        BUG_ON((start >> ord) >= max);
                        mb_set_bit(start >> ord, buddy);
                        e4b->bd_info->bb_counters[ord]--;
@@ -1989,6 +1994,7 @@ static int mb_mark_used(struct ext4_buddy *e4b, struct ext4_free_extent *ex)
                mb_clear_bit(cur + 1, buddy);
                e4b->bd_info->bb_counters[ord]++;
                e4b->bd_info->bb_counters[ord]++;
+               split = true;
        }
        mb_set_largest_free_order(e4b->bd_sb, e4b->bd_info);