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Subject[PATCH] ext4: reuse order and buddy in mb_mark_used when buddy split
Date
From: hanjinke <hanjinke.666@bytedance.com>

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 oder and buddy generated by the buddy split.

Reviewed by: lei.rao@intel.com
Signed-off-by: hanjinke <hanjinke.666@bytedance.com>
---
fs/ext4/mballoc.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 9f12f29bc346..c7ac6b269dd8 100644
--- 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);

--
2.20.1
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