md/raid1: skip data copy for behind io for discard request

discard request doesn't have data attached, so it's meaningless to
allocate memory and copy from original bio for behind IO. And the copy
is bogus because bio_copy_data_partial can't handle discard request.

We don't support writesame/writezeros request so far.

Reviewed-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Shaohua Li <shli@fb.com>

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index c6a671f13bc0b8a2a35915cad72c99dca94b6c6b..b7d9651286d4d73e3b24f208b1081e0a85308d53 100644 (file)
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1102,6 +1102,10 @@ static struct bio *alloc_behind_master_bio(struct r1bio *r1_bio,
        if (!behind_bio)
                goto fail;
 
+       /* discard op, we don't support writezero/writesame yet */
+       if (!bio_has_data(bio))
+               goto skip_copy;
+
        while (i < vcnt && size) {
                struct page *page;
                int len = min_t(int, PAGE_SIZE, size);
@@ -1118,7 +1122,7 @@ static struct bio *alloc_behind_master_bio(struct r1bio *r1_bio,
 
        bio_copy_data_partial(behind_bio, bio, offset,
                              behind_bio->bi_iter.bi_size);
-
+skip_copy:
        r1_bio->behind_master_bio = behind_bio;;
        set_bit(R1BIO_BehindIO, &r1_bio->state);