[Qemu-devel] Re: [PATCH 38/41] virtio-blk: use QLIST for the list of requests

[Michael S. Tsirkin]

On Wed, Dec 02, 2009 at 01:04:36PM +0100, Juan Quintela wrote:
> viltio_blak_dma_restart_bh() was unsafe, it used req->next after having
> (possible) put req in another list
> 
> Signed-off-by: Juan Quintela <address@hidden>

Sounds good, but why is this part of vmstate patchset?

> ---
>  hw/virtio-blk.c |   29 ++++++++++++++---------------
>  1 files changed, 14 insertions(+), 15 deletions(-)
> 
> diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
> index b716a36..838ec32 100644
> --- a/hw/virtio-blk.c
> +++ b/hw/virtio-blk.c
> @@ -26,7 +26,7 @@ typedef struct VirtIOBlock
>      VirtIODevice vdev;
>      BlockDriverState *bs;
>      VirtQueue *vq;
> -    VirtIOBlockReq *rq;
> +    QLIST_HEAD (,VirtIOBlockReq) rq;
>      char serial_str[BLOCK_SERIAL_STRLEN + 1];
>      QEMUBH *bh;
>      size_t config_size;
> @@ -81,7 +81,7 @@ struct VirtIOBlockReq
>      struct virtio_blk_outhdr *out;
>      struct virtio_scsi_inhdr *scsi;
>      QEMUIOVector qiov;
> -    struct VirtIOBlockReq *next;
> +    QLIST_ENTRY(VirtIOBlockReq) next;
>  };
> 
>  static void virtio_blk_req_complete(VirtIOBlockReq *req, int status)
> @@ -105,8 +105,7 @@ static int virtio_blk_handle_write_error(VirtIOBlockReq 
> *req, int error)
> 
>      if ((error == ENOSPC && action == BLOCK_ERR_STOP_ENOSPC)
>              || action == BLOCK_ERR_STOP_ANY) {
> -        req->next = s->rq;
> -        s->rq = req;
> +        QLIST_INSERT_HEAD(&s->rq, req, next);
>          vm_stop(0);
>      } else {
>          virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
> @@ -366,17 +365,19 @@ static void virtio_blk_handle_output(VirtIODevice 
> *vdev, VirtQueue *vq)
>  static void virtio_blk_dma_restart_bh(void *opaque)
>  {
>      VirtIOBlock *s = opaque;
> -    VirtIOBlockReq *req = s->rq;
> +    QLIST_HEAD (, VirtIOBlockReq) rq_copy;
> +    VirtIOBlockReq *req, *next_req;
> 
>      qemu_bh_delete(s->bh);
>      s->bh = NULL;
> 
> -    s->rq = NULL;
> +    QLIST_COPY_HEAD(&rq_copy, &s->rq);
> +    QLIST_INIT(&s->rq);
> 
> -    while (req) {
> +    QLIST_FOREACH_SAFE(req, &rq_copy, next, next_req) {
> +        QLIST_REMOVE(req, next);
>          bdrv_aio_writev(req->dev->bs, req->out->sector, &req->qiov,
>              req->qiov.size / 512, virtio_blk_rw_complete, req);
> -        req = req->next;
>      }
>  }
> 
> @@ -451,14 +452,13 @@ static uint32_t virtio_blk_get_features(VirtIODevice 
> *vdev)
>  static void virtio_blk_save(QEMUFile *f, void *opaque)
>  {
>      VirtIOBlock *s = opaque;
> -    VirtIOBlockReq *req = s->rq;
> +    VirtIOBlockReq *req;;
> 
>      virtio_save(&s->vdev, f);
> -    
> -    while (req) {
> +
> +    QLIST_FOREACH(req, &s->rq, next) {
>          qemu_put_sbyte(f, 1);
>          qemu_put_buffer(f, (unsigned char*)&req->elem, sizeof(req->elem));
> -        req = req->next;
>      }
>      qemu_put_sbyte(f, 0);
>  }
> @@ -474,8 +474,7 @@ static int virtio_blk_load(QEMUFile *f, void *opaque, int 
> version_id)
>      while (qemu_get_sbyte(f)) {
>          VirtIOBlockReq *req = virtio_blk_alloc_request(s);
>          qemu_get_buffer(f, (unsigned char*)&req->elem, sizeof(req->elem));
> -        req->next = s->rq;
> -        s->rq = req->next;
> +        QLIST_INSERT_HEAD(&s->rq, req, next);
>      }
> 
>      return 0;
> @@ -499,7 +498,7 @@ VirtIODevice *virtio_blk_init(DeviceState *dev, DriveInfo 
> *dinfo)
>      s->vdev.get_features = virtio_blk_get_features;
>      s->vdev.reset = virtio_blk_reset;
>      s->bs = dinfo->bdrv;
> -    s->rq = NULL;
> +    QLIST_INIT(&s->rq);
>      if (strlen(ps))
>          strncpy(s->serial_str, ps, sizeof(s->serial_str));
>      else
> -- 
> 1.6.5.2