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. The specification change list here: https://github.com/oasis-tcs/virtio-spec CHANGELOG: v3: finalized the specification change. Signed-off-by: Changpeng Liu <[email protected]> --- 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; + u32 block_size = queue_logical_block_size(req->q); + struct virtio_blk_discard_write_zeroes *range; + struct bio *bio; + + if (block_size < 512 || !block_size) + return -1; + + range = kmalloc_array(segments, sizeof(*range), GFP_ATOMIC); + 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; + + 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); + n++; + } + + if (WARN_ON_ONCE(n != segments)) { + 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; + } + 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) + */ + __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; +}; + #ifndef VIRTIO_BLK_NO_LEGACY struct virtio_scsi_inhdr { __virtio32 errors; -- 1.9.3 _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
