On Fri, Mar 30, 2018 at 08:49:34AM +0800, Changpeng Liu wrote: > Existing virtio-blk protocol doesn't have DISCARD/WRITE ZEROES > command support, this will impact the performance when using SSD > backend over file systems. > > The idea here is using 16 Bytes payload as one descriptor for > DISCARD/WRITE ZEROES command, users can put several ranges into > one command, for the purpose to support such feature, two feature > flags VIRTIO_BLK_F_DISCARD/VIRTIO_BLK_F_WRITE_ZEROES and two > commands VIRTIO_BLK_T_DISCARD/VIRTIO_BLK_T_WRITE_ZEROES are > introduced, and some parameters are added to the configuration > space to tell the OS the granularity of DISCARD/WRITE ZEROES > commands.
Pls fix grammar in this comment, I am not sure what are you trying to say. > > The specification change list here: > https://github.com/oasis-tcs/virtio-spec Which commit? > CHANGELOG: > v3: finalized the specification change. Changelog belongs after -- and should be complete including changes v1 to v2. > Signed-off-by: Changpeng Liu <changpeng....@intel.com> > --- > drivers/block/virtio_blk.c | 96 > +++++++++++++++++++++++++++++++++++++++-- > include/uapi/linux/virtio_blk.h | 39 +++++++++++++++++ > 2 files changed, 132 insertions(+), 3 deletions(-) > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > index 4a07593c..1943adb 100644 > --- a/drivers/block/virtio_blk.c > +++ b/drivers/block/virtio_blk.c > @@ -172,10 +172,53 @@ static int virtblk_add_req(struct virtqueue *vq, struct > virtblk_req *vbr, > return virtqueue_add_sgs(vq, sgs, num_out, num_in, vbr, GFP_ATOMIC); > } > > +static inline int virtblk_setup_discard_write_zeroes(struct request *req, > bool unmap) > +{ > + unsigned short segments = blk_rq_nr_discard_segments(req), n = 0; Split on two lines pls: unsigned short n = 0; > + u32 block_size = queue_logical_block_size(req->q); Seems to be unused except for the sanity check below. Why? > + struct virtio_blk_discard_write_zeroes *range; > + struct bio *bio; > + > + if (block_size < 512 || !block_size) Why 512? And when is it 0? > + return -1; -1 isn't a normal errno code. > + > + range = kmalloc_array(segments, sizeof(*range), GFP_ATOMIC); This might be pretty large: with 64K segments it looks like you are trying to allocate ~1Mbyte with GFP_ATOMIC which is unlikely to succeed. Can we split this up in chunks? > + if (!range) > + return -1; > + > + __rq_for_each_bio(bio, req) { > + u64 sector = bio->bi_iter.bi_sector; > + u32 num_sectors = bio->bi_iter.bi_size >> 9; why 9? > + > + range[n].flags.unmap = cpu_to_le32(unmap); > + range[n].flags.reserved = cpu_to_le32(0); > + range[n].num_sectors = cpu_to_le32(num_sectors); > + range[n].sector = cpu_to_le64(sector); Isn't this causing sparse warnings? > + n++; > + } > + > + if (WARN_ON_ONCE(n != segments)) { and when does this happen? > + kfree(range); > + return -1; > + } > + > + req->special_vec.bv_page = virt_to_page(range); > + req->special_vec.bv_offset = offset_in_page(range); > + req->special_vec.bv_len = sizeof(*range) * segments; > + req->rq_flags |= RQF_SPECIAL_PAYLOAD; > + > + return 0; > +} > + > static inline void virtblk_request_done(struct request *req) > { > struct virtblk_req *vbr = blk_mq_rq_to_pdu(req); > > + if (req->rq_flags & RQF_SPECIAL_PAYLOAD) { > + kfree(page_address(req->special_vec.bv_page) + > + req->special_vec.bv_offset); > + } > + > switch (req_op(req)) { > case REQ_OP_SCSI_IN: > case REQ_OP_SCSI_OUT: > @@ -225,6 +268,7 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx > *hctx, > int qid = hctx->queue_num; > int err; > bool notify = false; > + bool unmap = false; > u32 type; > > BUG_ON(req->nr_phys_segments + 2 > vblk->sg_elems); > @@ -237,6 +281,13 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx > *hctx, > case REQ_OP_FLUSH: > type = VIRTIO_BLK_T_FLUSH; > break; > + case REQ_OP_DISCARD: > + type = VIRTIO_BLK_T_DISCARD; > + break; > + case REQ_OP_WRITE_ZEROES: > + type = VIRTIO_BLK_T_WRITE_ZEROES; > + unmap = !(req->cmd_flags & REQ_NOUNMAP); > + break; > case REQ_OP_SCSI_IN: > case REQ_OP_SCSI_OUT: > type = VIRTIO_BLK_T_SCSI_CMD; > @@ -256,9 +307,16 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx > *hctx, > > blk_mq_start_request(req); > > + if (type == VIRTIO_BLK_T_DISCARD || type == VIRTIO_BLK_T_WRITE_ZEROES) { > + err = virtblk_setup_discard_write_zeroes(req, unmap); > + if (err) > + return BLK_STS_IOERR; Does a failure actually indicate an IO error? > + } > + > num = blk_rq_map_sg(hctx->queue, req, vbr->sg); > if (num) { > - if (rq_data_dir(req) == WRITE) > + if (rq_data_dir(req) == WRITE || type == VIRTIO_BLK_T_DISCARD || > + type == VIRTIO_BLK_T_WRITE_ZEROES) > vbr->out_hdr.type |= cpu_to_virtio32(vblk->vdev, > VIRTIO_BLK_T_OUT); > else > vbr->out_hdr.type |= cpu_to_virtio32(vblk->vdev, > VIRTIO_BLK_T_IN); > @@ -777,6 +835,38 @@ static int virtblk_probe(struct virtio_device *vdev) > if (!err && opt_io_size) > blk_queue_io_opt(q, blk_size * opt_io_size); > > + if (virtio_has_feature(vdev, VIRTIO_BLK_F_DISCARD)) { > + q->limits.discard_granularity = blk_size; > + > + virtio_cread(vdev, struct virtio_blk_config, > discard_sector_alignment, &v); > + if (v) > + q->limits.discard_alignment = v << 9; > + else > + q->limits.discard_alignment = 0; > + > + virtio_cread(vdev, struct virtio_blk_config, > max_discard_sectors, &v); > + if (v) > + blk_queue_max_discard_sectors(q, v); > + else > + blk_queue_max_discard_sectors(q, UINT_MAX); > + > + virtio_cread(vdev, struct virtio_blk_config, max_discard_seg, > &v); > + if (v) > + blk_queue_max_discard_segments(q, v); > + else > + blk_queue_max_discard_segments(q, USHRT_MAX); > + > + queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q); > + } > + > + if (virtio_has_feature(vdev, VIRTIO_BLK_F_WRITE_ZEROES)) { > + virtio_cread(vdev, struct virtio_blk_config, > max_write_zeroes_sectors, &v); > + if (v) > + blk_queue_max_write_zeroes_sectors(q, v); > + else > + blk_queue_max_write_zeroes_sectors(q, UINT_MAX); > + } > + > virtblk_update_capacity(vblk, false); > virtio_device_ready(vdev); > > @@ -885,14 +975,14 @@ static int virtblk_restore(struct virtio_device *vdev) > VIRTIO_BLK_F_SCSI, > #endif > VIRTIO_BLK_F_FLUSH, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE, > - VIRTIO_BLK_F_MQ, > + VIRTIO_BLK_F_MQ, VIRTIO_BLK_F_DISCARD, VIRTIO_BLK_F_WRITE_ZEROES, > } > ; > static unsigned int features[] = { > VIRTIO_BLK_F_SEG_MAX, VIRTIO_BLK_F_SIZE_MAX, VIRTIO_BLK_F_GEOMETRY, > VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE, > VIRTIO_BLK_F_FLUSH, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE, > - VIRTIO_BLK_F_MQ, > + VIRTIO_BLK_F_MQ, VIRTIO_BLK_F_DISCARD, VIRTIO_BLK_F_WRITE_ZEROES, > }; > > static struct virtio_driver virtio_blk = { > diff --git a/include/uapi/linux/virtio_blk.h b/include/uapi/linux/virtio_blk.h > index 9ebe4d9..78a60e6 100644 > --- a/include/uapi/linux/virtio_blk.h > +++ b/include/uapi/linux/virtio_blk.h > @@ -38,6 +38,8 @@ > #define VIRTIO_BLK_F_BLK_SIZE 6 /* Block size of disk is > available*/ > #define VIRTIO_BLK_F_TOPOLOGY 10 /* Topology information is > available */ > #define VIRTIO_BLK_F_MQ 12 /* support more than one vq */ > +#define VIRTIO_BLK_F_DISCARD 13 /* DISCARD command is supported */ > +#define VIRTIO_BLK_F_WRITE_ZEROES 14 /* WRITE ZEROES command is > supported */ > > /* Legacy feature bits */ > #ifndef VIRTIO_BLK_NO_LEGACY > @@ -86,6 +88,22 @@ struct virtio_blk_config { > > /* number of vqs, only available when VIRTIO_BLK_F_MQ is set */ > __u16 num_queues; > + /* The maximum discard segment size (if VIRTIO_BLK_F_DISCARD) */ > + __u32 max_discard_sectors; > + /* The maximum number of discard segments (if VIRTIO_BLK_F_DISCARD) */ > + __u32 max_discard_seg; > + /* The sector alignment for discard (if VIRTIO_BLK_F_DISCARD) */ > + __u32 discard_sector_alignment; > + /* The maximum number of write zeroes sectors (if > VIRTIO_BLK_F_WRITE_ZEROES) */ > + __u32 max_write_zeroes_sectors; > + /* The maximum number of write zeroes segments (if > VIRTIO_BLK_F_WRITE_ZEROES) */ > + __u32 max_write_zeroes_seg; > + /* Device clear this bit when write zeroes command cannot result in > + * deallocating one or more sectors > + * (if VIRTIO_BLK_F_WRITE_ZEROES with unmap bit) Pls fix grammar in this comment, I am not sure what are you trying to say. > + */ > + __u8 write_zeroes_may_unmap; > + __u8 unused1[3]; > } __attribute__((packed)); > > /* > @@ -114,6 +132,12 @@ struct virtio_blk_config { > /* Get device ID command */ > #define VIRTIO_BLK_T_GET_ID 8 > > +/* Discard command */ > +#define VIRTIO_BLK_T_DISCARD 11 > + > +/* Write zeroes command */ > +#define VIRTIO_BLK_T_WRITE_ZEROES 13 > + > #ifndef VIRTIO_BLK_NO_LEGACY > /* Barrier before this op. */ > #define VIRTIO_BLK_T_BARRIER 0x80000000 > @@ -133,6 +157,21 @@ struct virtio_blk_outhdr { > __virtio64 sector; > }; > > +/* > + * discard/write zeroes range for each request. > + */ > +struct virtio_blk_discard_write_zeroes { > + /* discard/write zeroes start sector */ > + __virtio64 sector; > + /* number of discard/write zeroes sectors */ > + __virtio32 num_sectors; > + /* valid for write zeroes command */ > + struct { > + __virtio32 unmap:1; > + __virtio32 reserved:31; > + } flags; > +}; > + You can't use bitmaps in portable code. The format differs between architectures. > #ifndef VIRTIO_BLK_NO_LEGACY > struct virtio_scsi_inhdr { > __virtio32 errors; > -- > 1.9.3 _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
