Re: [Qemu-devel] [PATCH 2/2] block/nvme: add support for discard

[Maxim Levitsky]

On Tue, 2019-08-27 at 18:29 -0400, John Snow wrote:
> 
> On 8/25/19 3:15 AM, Maxim Levitsky wrote:
> > Signed-off-by: Maxim Levitsky <address@hidden>
> > ---
> >  block/nvme.c       | 83 ++++++++++++++++++++++++++++++++++++++++++++++
> >  block/trace-events |  2 ++
> >  2 files changed, 85 insertions(+)
> > 
> > diff --git a/block/nvme.c b/block/nvme.c
> > index f8bd11e19a..dd041f39c9 100644
> > --- a/block/nvme.c
> > +++ b/block/nvme.c
> > @@ -112,6 +112,7 @@ typedef struct {
> >      bool plugged;
> >  
> >      bool supports_write_zeros;
> > +    bool supports_discard;
> >  
> >      CoMutex dma_map_lock;
> >      CoQueue dma_flush_queue;
> > @@ -463,6 +464,7 @@ static void nvme_identify(BlockDriverState *bs, int 
> > namespace, Error **errp)
> >  
> >      oncs = le16_to_cpu(idctrl->oncs);
> >      s->supports_write_zeros = (oncs & NVME_ONCS_WRITE_ZEROS) != 0;
> > +    s->supports_discard = (oncs & NVME_ONCS_DSM) != 0;
> 
> Same comment -- checking !!(register & FIELD) is nicer than the
> negative. (I'm actually not sure even the !! is needed, but it seems to
> be a QEMU-ism and I've caught myself using it...)

All right, no problem to use !!

> 
> Rest looks good to me on a skim, but I'm not very well-versed in NVME.
Thanks!


> 
> >  
> >      memset(resp, 0, 4096);
> >  
> > @@ -1153,6 +1155,86 @@ static coroutine_fn int 
> > nvme_co_pwrite_zeroes(BlockDriverState *bs,
> >  }
> >  
> >  
> > +static int coroutine_fn nvme_co_pdiscard(BlockDriverState *bs,
> > +                                         int64_t offset,
> > +                                         int bytes)
> > +{
> > +    BDRVNVMeState *s = bs->opaque;
> > +    NVMeQueuePair *ioq = s->queues[1];
> > +    NVMeRequest *req;
> > +    NvmeDsmRange *buf;
> > +    QEMUIOVector local_qiov;
> > +    int ret;
> > +
> > +    NvmeCmd cmd = {
> > +        .opcode = NVME_CMD_DSM,
> > +        .nsid = cpu_to_le32(s->nsid),
> > +        .cdw10 = cpu_to_le32(0), /*number of ranges - 0 based*/
> > +        .cdw11 = cpu_to_le32(1 << 2), /*deallocate bit*/
> > +    };
> > +
> > +    NVMeCoData data = {
> > +        .ctx = bdrv_get_aio_context(bs),
> > +        .ret = -EINPROGRESS,
> > +    };
> > +
> > +    if (!s->supports_discard) {
> > +        return -ENOTSUP;
> > +    }
> > +
> > +    assert(s->nr_queues > 1);
> > +
> > +    buf = qemu_try_blockalign0(bs, s->page_size);
> > +    if (!buf) {
> > +        return -ENOMEM;
> > +    }
> > +
> > +    buf->nlb = cpu_to_le32(bytes >> s->blkshift);
> > +    buf->slba = cpu_to_le64(offset >> s->blkshift);
> > +    buf->cattr = 0;
> > +
> > +    qemu_iovec_init(&local_qiov, 1);
> > +    qemu_iovec_add(&local_qiov, buf, 4096);
> > +
> > +    req = nvme_get_free_req(ioq);
> > +    assert(req);
> > +
> > +    qemu_co_mutex_lock(&s->dma_map_lock);
> > +    ret = nvme_cmd_map_qiov(bs, &cmd, req, &local_qiov);
> > +    qemu_co_mutex_unlock(&s->dma_map_lock);
> > +
> > +    if (ret) {
> > +        req->busy = false;
> > +        goto out;
> > +    }
> > +
> > +    trace_nvme_dsm(s, offset, bytes);
> > +
> > +    nvme_submit_command(s, ioq, req, &cmd, nvme_rw_cb, &data);
> > +
> > +    data.co = qemu_coroutine_self();
> > +    while (data.ret == -EINPROGRESS) {
> > +        qemu_coroutine_yield();
> > +    }
> > +
> > +    qemu_co_mutex_lock(&s->dma_map_lock);
> > +    ret = nvme_cmd_unmap_qiov(bs, &local_qiov);
> > +    qemu_co_mutex_unlock(&s->dma_map_lock);
> > +
> > +    if (ret) {
> > +        goto out;
> > +    }
> > +
> > +    ret = data.ret;
> > +    trace_nvme_dsm_done(s, offset, bytes, ret);
> > +out:
> > +    qemu_iovec_destroy(&local_qiov);
> > +    qemu_vfree(buf);
> > +    return ret;
> > +
> > +}
> > +
> > +
> >  static int nvme_reopen_prepare(BDRVReopenState *reopen_state,
> >                                 BlockReopenQueue *queue, Error **errp)
> >  {
> > @@ -1259,6 +1341,7 @@ static BlockDriver bdrv_nvme = {
> >      .bdrv_co_pwritev          = nvme_co_pwritev,
> >  
> >      .bdrv_co_pwrite_zeroes    = nvme_co_pwrite_zeroes,
> > +    .bdrv_co_pdiscard         = nvme_co_pdiscard,
> >  
> >      .bdrv_co_flush_to_disk    = nvme_co_flush,
> >      .bdrv_reopen_prepare      = nvme_reopen_prepare,
> > diff --git a/block/trace-events b/block/trace-events
> > index 8209fbd0c7..7d1d48b502 100644
> > --- a/block/trace-events
> > +++ b/block/trace-events
> > @@ -153,6 +153,8 @@ nvme_write_zeros(void *s, uint64_t offset, uint64_t 
> > bytes, int flags) "s %p offs
> >  nvme_qiov_unaligned(const void *qiov, int n, void *base, size_t size, int 
> > align) "qiov %p n %d base %p size 0x%zx align 0x%x"
> >  nvme_prw_buffered(void *s, uint64_t offset, uint64_t bytes, int niov, int 
> > is_write) "s %p offset %"PRId64" bytes %"PRId64" niov %d is_write %d"
> >  nvme_rw_done(void *s, int is_write, uint64_t offset, uint64_t bytes, int 
> > ret) "s %p is_write %d offset %"PRId64" bytes %"PRId64" ret %d"
> > +nvme_dsm(void *s, uint64_t offset, uint64_t bytes) "s %p offset %"PRId64" 
> > bytes %"PRId64""
> > +nvme_dsm_done(void *s, uint64_t offset, uint64_t bytes, int ret) "s %p 
> > offset %"PRId64" bytes %"PRId64" ret %d"
> >  nvme_dma_map_flush(void *s) "s %p"
> >  nvme_free_req_queue_wait(void *q) "q %p"
> >  nvme_cmd_map_qiov(void *s, void *cmd, void *req, void *qiov, int entries) 
> > "s %p cmd %p req %p qiov %p entries %d"
> > 


Best regards,
        Maxim Levitsky