dm: simplify the single bio fast path in __send_duplicate_bios

Most targets just need a single flush bio.  Open code that case in
__send_duplicate_bios without the need to add the bio to a list.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Link: https://lore.kernel.org/r/20220202160109.108149-9-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index c05b6ff1bb957fa17649ddddfc8c4366d152e139..78df75f57288b9a27987d12ac7e90f02d495d9df 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1241,15 +1241,6 @@ static void alloc_multiple_bios(struct bio_list *blist, struct clone_info *ci,
        struct bio *bio;
        int try;
 
-       if (!num_bios)
-               return;
-
-       if (num_bios == 1) {
-               bio = alloc_tio(ci, ti, 0, len, GFP_NOIO);
-               bio_list_add(blist, bio);
-               return;
-       }
-
        for (try = 0; try < 2; try++) {
                int bio_nr;
 
@@ -1279,12 +1270,23 @@ static void __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti,
        struct bio_list blist = BIO_EMPTY_LIST;
        struct bio *clone;
 
-       alloc_multiple_bios(&blist, ci, ti, num_bios, len);
-
-       while ((clone = bio_list_pop(&blist))) {
+       switch (num_bios) {
+       case 0:
+               break;
+       case 1:
+               clone = alloc_tio(ci, ti, 0, len, GFP_NOIO);
                if (len)
                        bio_setup_sector(clone, ci->sector, *len);
                __map_bio(clone);
+               break;
+       default:
+               alloc_multiple_bios(&blist, ci, ti, num_bios, len);
+               while ((clone = bio_list_pop(&blist))) {
+                       if (len)
+                               bio_setup_sector(clone, ci->sector, *len);
+                       __map_bio(clone);
+               }
+               break;
        }
 }