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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 f313520 ("xen_disk: add discard support")

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
This commit is contained in:
Olaf Hering 2016-11-23 10:39:12 +00:00 committed by Stefano Stabellini
parent 00227fefd2
commit 7875efb9f6
1 changed files with 36 additions and 6 deletions
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42
hw/block/xen_disk.c
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@ -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: