Re: [Qemu-devel] [PATCH 4/5] virtio-blk: release reference to RAM's memoryRegion

[liu ping fan]

On Tue, Apr 2, 2013 at 1:58 PM, li guang <address@hidden> wrote:
> 在 2013-04-01一的 16:20 +0800，Liu Ping Fan写道：
>> From: Liu Ping Fan <address@hidden>
>>
>> virtio-blk will reference to RAM's memoryRegion when the req has been
>> done.
>
>   do you mean unreference after req completed?
>
Yes, should s/reference/unreference/

>> So we can avoid to call bdrv_drain_all() when RAM hot unplug.
>>
>> Signed-off-by: Liu Ping Fan <address@hidden>
>> ---
>>  hw/dataplane/virtio-blk.c |   52 
>> ++++++++++++++++++++++++++++++++++----------
>>  1 files changed, 40 insertions(+), 12 deletions(-)
>>
>> diff --git a/hw/dataplane/virtio-blk.c b/hw/dataplane/virtio-blk.c
>> index 1242d61..437174d 100644
>> --- a/hw/dataplane/virtio-blk.c
>> +++ b/hw/dataplane/virtio-blk.c
>> @@ -34,6 +34,8 @@ enum {
>>
>>  typedef struct {
>>      struct iocb iocb;               /* Linux AIO control block */
>> +    MemoryRegion *mrs[VRING_MAX];
>> +    int mrs_cnt;
>>      QEMUIOVector *inhdr;            /* iovecs for virtio_blk_inhdr */
>>      unsigned int head;              /* vring descriptor index */
>>      struct iovec *bounce_iov;       /* used if guest buffers are unaligned 
>> */
>> @@ -120,6 +122,9 @@ static void complete_request(struct iocb *iocb, ssize_t 
>> ret, void *opaque)
>>       * transferred plus the status bytes.
>>       */
>>      vring_push(&s->vring, req->head, len + sizeof(hdr));
>> +    while (--req->mrs_cnt >= 0) {
>> +        memory_region_unref(req->mrs[req->mrs_cnt]);
>> +    }
>>
>>      s->num_reqs--;
>>  }
>> @@ -155,7 +160,8 @@ static void do_get_id_cmd(VirtIOBlockDataPlane *s,
>>  static int do_rdwr_cmd(VirtIOBlockDataPlane *s, bool read,
>>                         struct iovec *iov, unsigned int iov_cnt,
>>                         long long offset, unsigned int head,
>> -                       QEMUIOVector *inhdr)
>> +                       QEMUIOVector *inhdr,
>> +                       MemoryRegion **mrs, int cnt)
>>  {
>>      struct iocb *iocb;
>>      QEMUIOVector qiov;
>> @@ -187,6 +193,8 @@ static int do_rdwr_cmd(VirtIOBlockDataPlane *s, bool 
>> read,
>>
>>      /* Fill in virtio block metadata needed for completion */
>>      VirtIOBlockRequest *req = container_of(iocb, VirtIOBlockRequest, iocb);
>> +    memcpy(req->mrs, mrs, cnt*sizeof(MemoryRegion *));
>> +    req->mrs_cnt = cnt;
>>      req->head = head;
>>      req->inhdr = inhdr;
>>      req->bounce_iov = bounce_iov;
>> @@ -196,19 +204,22 @@ static int do_rdwr_cmd(VirtIOBlockDataPlane *s, bool 
>> read,
>>
>>  static int process_request(IOQueue *ioq, struct iovec iov[],
>>                             unsigned int out_num, unsigned int in_num,
>> -                           unsigned int head)
>> +                           unsigned int head, MemoryRegion **mrs)
>>  {
>>      VirtIOBlockDataPlane *s = container_of(ioq, VirtIOBlockDataPlane, 
>> ioqueue);
>>      struct iovec *in_iov = &iov[out_num];
>>      struct virtio_blk_outhdr outhdr;
>>      QEMUIOVector *inhdr;
>>      size_t in_size;
>> +    unsigned int i, cnt = out_num+in_num;
>> +    int ret;
>>
>>      /* Copy in outhdr */
>>      if (unlikely(iov_to_buf(iov, out_num, 0, &outhdr,
>>                              sizeof(outhdr)) != sizeof(outhdr))) {
>>          error_report("virtio-blk request outhdr too short");
>> -        return -EFAULT;
>> +        ret = -EFAULT;
>> +        goto free_mrs;
>>      }
>>      iov_discard_front(&iov, &out_num, sizeof(outhdr));
>>
>> @@ -216,7 +227,8 @@ static int process_request(IOQueue *ioq, struct iovec 
>> iov[],
>>      in_size = iov_size(in_iov, in_num);
>>      if (in_size < sizeof(struct virtio_blk_inhdr)) {
>>          error_report("virtio_blk request inhdr too short");
>> -        return -EFAULT;
>> +        ret = -EFAULT;
>> +        goto free_mrs;
>>      }
>>      inhdr = g_slice_new(QEMUIOVector);
>>      qemu_iovec_init(inhdr, 1);
>> @@ -229,18 +241,22 @@ static int process_request(IOQueue *ioq, struct iovec 
>> iov[],
>>      outhdr.type &= ~VIRTIO_BLK_T_BARRIER;
>>
>>      switch (outhdr.type) {
>> +    /* For VIRTIO_BLK_T_IN/OUT, MemoryRegion will be release when cb */
>>      case VIRTIO_BLK_T_IN:
>> -        do_rdwr_cmd(s, true, in_iov, in_num, outhdr.sector * 512, head, 
>> inhdr);
>> +        do_rdwr_cmd(s, true, in_iov, in_num, outhdr.sector * 512, head, 
>> inhdr,
>> +            mrs, cnt);
>>          return 0;
>>
>>      case VIRTIO_BLK_T_OUT:
>> -        do_rdwr_cmd(s, false, iov, out_num, outhdr.sector * 512, head, 
>> inhdr);
>> +        do_rdwr_cmd(s, false, iov, out_num, outhdr.sector * 512, head, 
>> inhdr,
>> +            mrs, cnt);
>>          return 0;
>>
>>      case VIRTIO_BLK_T_SCSI_CMD:
>>          /* TODO support SCSI commands */
>>          complete_request_early(s, head, inhdr, VIRTIO_BLK_S_UNSUPP);
>> -        return 0;
>> +        ret = 0;
>> +        goto free_mrs;
>
> IMHO, 's/goto free_mrs/break/g', so free_mrs label can be removed.
>
Adopt.  Thanks.
Pingfan
>>
>>      case VIRTIO_BLK_T_FLUSH:
>>          /* TODO fdsync not supported by Linux AIO, do it synchronously 
>> here! */
>> @@ -249,18 +265,27 @@ static int process_request(IOQueue *ioq, struct iovec 
>> iov[],
>>          } else {
>>              complete_request_early(s, head, inhdr, VIRTIO_BLK_S_OK);
>>          }
>> -        return 0;
>> +        ret = 0;
>> +        goto free_mrs;
>>
>>      case VIRTIO_BLK_T_GET_ID:
>>          do_get_id_cmd(s, in_iov, in_num, head, inhdr);
>> -        return 0;
>> +        ret = 0;
>> +        goto free_mrs;
>>
>>      default:
>>          error_report("virtio-blk unsupported request type %#x", 
>> outhdr.type);
>>          qemu_iovec_destroy(inhdr);
>>          g_slice_free(QEMUIOVector, inhdr);
>> -        return -EFAULT;
>> +        ret = -EFAULT;
>> +        goto free_mrs;
>> +    }
>> +
>> +free_mrs:
>> +    for (i = 0; i < cnt; i++) {
>> +        memory_region_unref(mrs[i]);
>>      }
>> +    return ret;
>>  }
>>
>>  static int flush_true(EventNotifier *e)
>> @@ -286,6 +311,7 @@ static void handle_notify(EventNotifier *e)
>>      struct iovec iovec[VRING_MAX];
>>      struct iovec *end = &iovec[VRING_MAX];
>>      struct iovec *iov = iovec;
>> +    MemoryRegion *mrs[VRING_MAX];
>>
>>      /* When a request is read from the vring, the index of the first 
>> descriptor
>>       * (aka head) is returned so that the completed request can be pushed 
>> onto
>> @@ -304,7 +330,8 @@ static void handle_notify(EventNotifier *e)
>>          vring_disable_notification(s->vdev, &s->vring);
>>
>>          for (;;) {
>> -            head = vring_pop(s->vdev, &s->vring, iov, end, &out_num, 
>> &in_num);
>> +            head = vring_pop(s->vdev, &s->vring, iov, end, &out_num, 
>> &in_num,
>> +                            mrs);
>>              if (head < 0) {
>>                  break; /* no more requests */
>>              }
>> @@ -312,7 +339,8 @@ static void handle_notify(EventNotifier *e)
>>              trace_virtio_blk_data_plane_process_request(s, out_num, in_num,
>>                                                          head);
>>
>> -            if (process_request(&s->ioqueue, iov, out_num, in_num, head) < 
>> 0) {
>> +            if (process_request(&s->ioqueue, iov, out_num, in_num, head,
>> +                    mrs) < 0) {
>>                  vring_set_broken(&s->vring);
>>                  break;
>>              }
>
>