Hi,
On Mon, 24 Sep 2012 14:56:39 +1000, NeilBrown wrote:
> Hi Jens,
> this patch has been sitting in my -next tree for a little while and I was
> hoping for it to go in for the next merge window.
> It simply allows bio_split() to be used on bios without a payload, such as
> 'discard'.
> Are you happy with it going in though my 'md' tree, or would you rather take
> it though your 'block' tree?
>
> Thanks,
> NeilBrown
>
>
> From: Shaohua Li <s...@fusionio.com>
> Date: Thu, 20 Sep 2012 09:36:03 +1000
> Subject: [PATCH] block: makes bio_split support bio without data
>
> discard bio hasn't data attached. We hit a BUG_ON with such bio. This makes
> bio_split works for such bio.
>
> Signed-off-by: Shaohua Li <s...@fusionio.com>
> Signed-off-by: NeilBrown <ne...@suse.de>
>
> diff --git a/fs/bio.c b/fs/bio.c
> index 71072ab..dbb7a6c 100644
> --- a/fs/bio.c
> +++ b/fs/bio.c
> @@ -1501,7 +1501,7 @@ struct bio_pair *bio_split(struct bio *bi, int
> first_sectors)
> trace_block_split(bdev_get_queue(bi->bi_bdev), bi,
> bi->bi_sector + first_sectors);
>
> - BUG_ON(bi->bi_vcnt != 1);
> + BUG_ON(bi->bi_vcnt != 1 && bi->bi_vcnt != 0);
Why not
BUG_ON(bi->bi_vcnt > 1);
?
Thanks,
Namhyung
> BUG_ON(bi->bi_idx != 0);
> atomic_set(&bp->cnt, 3);
> bp->error = 0;
> @@ -1511,17 +1511,19 @@ struct bio_pair *bio_split(struct bio *bi, int
> first_sectors)
> bp->bio2.bi_size -= first_sectors << 9;
> bp->bio1.bi_size = first_sectors << 9;
>
> - bp->bv1 = bi->bi_io_vec[0];
> - bp->bv2 = bi->bi_io_vec[0];
> - bp->bv2.bv_offset += first_sectors << 9;
> - bp->bv2.bv_len -= first_sectors << 9;
> - bp->bv1.bv_len = first_sectors << 9;
> + if (bi->bi_vcnt != 0) {
> + bp->bv1 = bi->bi_io_vec[0];
> + bp->bv2 = bi->bi_io_vec[0];
> + bp->bv2.bv_offset += first_sectors << 9;
> + bp->bv2.bv_len -= first_sectors << 9;
> + bp->bv1.bv_len = first_sectors << 9;
>
> - bp->bio1.bi_io_vec = &bp->bv1;
> - bp->bio2.bi_io_vec = &bp->bv2;
> + bp->bio1.bi_io_vec = &bp->bv1;
> + bp->bio2.bi_io_vec = &bp->bv2;
>
> - bp->bio1.bi_max_vecs = 1;
> - bp->bio2.bi_max_vecs = 1;
> + bp->bio1.bi_max_vecs = 1;
> + bp->bio2.bi_max_vecs = 1;
> + }
>
> bp->bio1.bi_end_io = bio_pair_end_1;
> bp->bio2.bi_end_io = bio_pair_end_2;
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