From f484697e619a83ecc370443a34746379ad99d204 Mon Sep 17 00:00:00 2001 From: Ming-Hung Tsai Date: Tue, 22 Oct 2024 15:13:39 +0800 Subject: [PATCH] dm cache: optimize dirty bit checking with find_next_bit when resizing When shrinking the fast device, dm-cache iteratively searches for a dirty bit among the cache blocks to be dropped, which is less efficient. Use find_next_bit instead, as it is twice as fast as the iterative approach with test_bit. Signed-off-by: Ming-Hung Tsai Fixes: f494a9c6b1b6 ("dm cache: cache shrinking support") Cc: stable@vger.kernel.org Signed-off-by: Mikulas Patocka Acked-by: Joe Thornber --- drivers/md/dm-cache-target.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index 1fcd8c5c220e..fa8ef2c32af8 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -2911,14 +2911,14 @@ static bool can_resize(struct cache *cache, dm_cblock_t new_size) /* * We can't drop a dirty block when shrinking the cache. */ - while (from_cblock(new_size) < from_cblock(cache->cache_size)) { - if (is_dirty(cache, new_size)) { - DMERR("%s: unable to shrink cache; cache block %llu is dirty", - cache_device_name(cache), - (unsigned long long) from_cblock(new_size)); - return false; - } - new_size = to_cblock(from_cblock(new_size) + 1); + new_size = to_cblock(find_next_bit(cache->dirty_bitset, + from_cblock(cache->cache_size), + from_cblock(new_size))); + if (new_size != cache->cache_size) { + DMERR("%s: unable to shrink cache; cache block %llu is dirty", + cache_device_name(cache), + (unsigned long long) from_cblock(new_size)); + return false; } return true;