From af822aa68fbdf0a480a17462ed70232998127453 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Mon, 17 Aug 2020 17:52:40 +0800 Subject: [PATCH] block: virtio_blk: fix handling single range discard request 1f23816b8eb8 ("virtio_blk: add discard and write zeroes support") starts to support multi-range discard for virtio-blk. However, the virtio-blk disk may report max discard segment as 1, at least that is exactly what qemu is doing. So far, block layer switches to normal request merge if max discard segment limit is 1, and multiple bios can be merged to single segment. This way may cause memory corruption in virtblk_setup_discard_write_zeroes(). Fix the issue by handling single max discard segment in straightforward way. Fixes: 1f23816b8eb8 ("virtio_blk: add discard and write zeroes support") Signed-off-by: Ming Lei Reviewed-by: Christoph Hellwig Cc: Changpeng Liu Cc: Daniel Verkamp Cc: Michael S. Tsirkin Cc: Stefan Hajnoczi Cc: Stefano Garzarella Signed-off-by: Jens Axboe --- drivers/block/virtio_blk.c | 29 ++++++++++++++++++++++------- 1 file changed, 22 insertions(+), 7 deletions(-) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 63b213e00b37..b2e48dac1ebd 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -126,16 +126,31 @@ static int virtblk_setup_discard_write_zeroes(struct request *req, bool unmap) if (!range) return -ENOMEM; - __rq_for_each_bio(bio, req) { - u64 sector = bio->bi_iter.bi_sector; - u32 num_sectors = bio->bi_iter.bi_size >> SECTOR_SHIFT; + /* + * Single max discard segment means multi-range discard isn't + * supported, and block layer only runs contiguity merge like + * normal RW request. So we can't reply on bio for retrieving + * each range info. + */ + if (queue_max_discard_segments(req->q) == 1) { + range[0].flags = cpu_to_le32(flags); + range[0].num_sectors = cpu_to_le32(blk_rq_sectors(req)); + range[0].sector = cpu_to_le64(blk_rq_pos(req)); + n = 1; + } else { + __rq_for_each_bio(bio, req) { + u64 sector = bio->bi_iter.bi_sector; + u32 num_sectors = bio->bi_iter.bi_size >> SECTOR_SHIFT; - range[n].flags = cpu_to_le32(flags); - range[n].num_sectors = cpu_to_le32(num_sectors); - range[n].sector = cpu_to_le64(sector); - n++; + range[n].flags = cpu_to_le32(flags); + range[n].num_sectors = cpu_to_le32(num_sectors); + range[n].sector = cpu_to_le64(sector); + n++; + } } + WARN_ON_ONCE(n != segments); + req->special_vec.bv_page = virt_to_page(range); req->special_vec.bv_offset = offset_in_page(range); req->special_vec.bv_len = sizeof(*range) * segments;