Commit 7875efb9 authored by Olaf Hering's avatar Olaf Hering Committed by Stefano Stabellini
Browse files

xen_disk: split discard input to match internal representation 



The guest sends discard requests as u64 sector/count pairs, but the
block layer operates internally with s64/s32 pairs. The conversion
leads to IO errors in the guest, the discard request is not processed.

  domU.cfg:
  'vdev=xvda, format=qcow2, backendtype=qdisk, target=/x.qcow2'
  domU:
  mkfs.ext4 -F /dev/xvda
  Discarding device blocks: failed - Input/output error

Fix this by splitting the request into chunks of BDRV_REQUEST_MAX_SECTORS.
Add input range checking to avoid overflow.

Fixes f3135204 ("xen_disk: add discard support")

Signed-off-by: default avatarOlaf Hering <olaf@aepfle.de>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
Reviewed-by: default avatarStefano Stabellini <sstabellini@kernel.org>
parent 00227fef

hw/block/xen_disk.c

+36 −6
Original line number Diff line number Diff line
@@ -660,6 +660,38 @@ static void qemu_aio_complete(void *opaque, int ret) 
    qemu_bh_schedule(ioreq->blkdev->bh);

}



static bool blk_split_discard(struct ioreq *ioreq, blkif_sector_t sector_number,

                              uint64_t nr_sectors)

{

    struct XenBlkDev *blkdev = ioreq->blkdev;

    int64_t byte_offset;

    int byte_chunk;

    uint64_t byte_remaining, limit;

    uint64_t sec_start = sector_number;

    uint64_t sec_count = nr_sectors;



    /* Wrap around, or overflowing byte limit? */

    if (sec_start + sec_count < sec_count ||

        sec_start + sec_count > INT64_MAX >> BDRV_SECTOR_BITS) {

        return false;

    }



    limit = BDRV_REQUEST_MAX_SECTORS << BDRV_SECTOR_BITS;

    byte_offset = sec_start << BDRV_SECTOR_BITS;

    byte_remaining = sec_count << BDRV_SECTOR_BITS;



    do {

        byte_chunk = byte_remaining > limit ? limit : byte_remaining;

        ioreq->aio_inflight++;

        blk_aio_pdiscard(blkdev->blk, byte_offset, byte_chunk,

                         qemu_aio_complete, ioreq);

        byte_remaining -= byte_chunk;

        byte_offset += byte_chunk;

    } while (byte_remaining > 0);



    return true;

}



static int ioreq_runio_qemu_aio(struct ioreq *ioreq)

{

    struct XenBlkDev *blkdev = ioreq->blkdev;
@@ -708,12 +740,10 @@ static int ioreq_runio_qemu_aio(struct ioreq *ioreq) 
        break;

    case BLKIF_OP_DISCARD:

    {

        struct blkif_request_discard *discard_req = (void *)&ioreq->req;

        ioreq->aio_inflight++;

        blk_aio_pdiscard(blkdev->blk,

                         discard_req->sector_number << BDRV_SECTOR_BITS,

                         discard_req->nr_sectors << BDRV_SECTOR_BITS,

                         qemu_aio_complete, ioreq);

        struct blkif_request_discard *req = (void *)&ioreq->req;

        if (!blk_split_discard(ioreq, req->sector_number, req->nr_sectors)) {

            goto err;

        }

        break;

    }

    default: