From: Changpeng Liu <changpeng.liu@xxxxxxxxx> In commit 88c85538, "virtio-blk: add discard and write zeroes features to specification" (https://github.com/oasis-tcs/virtio-spec), the virtio block specification has been extended to add VIRTIO_BLK_T_DISCARD and VIRTIO_BLK_T_WRITE_ZEROES commands. This patch enables support for discard and write zeroes in the virtio-blk driver when the device advertises the corresponding features, VIRTIO_BLK_F_DISCARD and VIRTIO_BLK_F_WRITE_ZEROES. Signed-off-by: Changpeng Liu <changpeng.liu@xxxxxxxxx> Signed-off-by: Daniel Verkamp <dverkamp@xxxxxxxxxxxx> --- dverkamp: I've picked up this patch and made a few minor changes (as listed below); most notably, I changed the kmalloc back to GFP_ATOMIC, since it can be called from a context where sleeping is not allowed. To prevent large allocations, I've also clamped the maximum number of discard segments to 256; this results in a 4K allocation and should be plenty of descriptors for most use cases. I also removed most of the description from the commit message, since it was duplicating the comments from virtio_blk.h and quoting parts of the spec without adding any extra information. I have tested this iteration of the patch using crosvm with modifications to enable the new features: https://chromium.googlesource.com/chromiumos/platform/crosvm/ CHANGELOG: v8: [dverkamp] replace shifts by 9 with SECTOR_SHIFT constant v7: [dverkamp] use GFP_ATOMIC for allocation that may not sleep; clarify descriptor flags field; comment wording cleanups. v6: don't set T_OUT bit to discard and write zeroes commands. v5: use new block layer API: blk_queue_flag_set. v4: several optimizations based on MST's comments, remove bit field usage for command descriptor. v3: define the virtio-blk protocol to add discard and write zeroes support, first version implementation based on proposed specification. v2: add write zeroes command support. v1: initial proposal implementation for discard command. --- drivers/block/virtio_blk.c | 95 ++++++++++++++++++++++++++++++++- include/uapi/linux/virtio_blk.h | 54 +++++++++++++++++++ 2 files changed, 147 insertions(+), 2 deletions(-) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 23752dc99b00..04a7ae602e2f 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -18,6 +18,7 @@ #define PART_BITS 4 #define VQ_NAME_LEN 16 +#define MAX_DISCARD_SEGMENTS 256 static int major; static DEFINE_IDA(vd_index_ida); @@ -172,10 +173,50 @@ 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); + unsigned short n = 0; + struct virtio_blk_discard_write_zeroes *range; + struct bio *bio; + u32 flags = 0; + + if (unmap) + flags |= VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP; + + range = kmalloc_array(segments, sizeof(*range), GFP_ATOMIC); + if (!range) + return -ENOMEM; + + __rq_for_each_bio(bio, req) { + u64 sector = bio->bi_iter.bi_sector; + u32 num_sectors = bio->bi_iter.bi_size >> SECTOR_SHIFT; + + range[n].flags = cpu_to_le32(flags); + range[n].num_sectors = cpu_to_le32(num_sectors); + range[n].sector = cpu_to_le64(sector); + n++; + } + + 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 +266,7 @@ 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 +279,13 @@ 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; @@ -256,6 +305,12 @@ 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_RESOURCE; + } + num = blk_rq_map_sg(hctx->queue, req, vbr->sg); if (num) { if (rq_data_dir(req) == WRITE) @@ -777,6 +832,42 @@ 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 << SECTOR_SHIFT; + 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 && v <= MAX_DISCARD_SEGMENTS) + blk_queue_max_discard_segments(q, v); + else + blk_queue_max_discard_segments(q, MAX_DISCARD_SEGMENTS); + + blk_queue_flag_set(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 +976,14 @@ static unsigned int features_legacy[] = { 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 9ebe4d968dd5..682afbfe3aa4 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 is supported */ +#define VIRTIO_BLK_F_WRITE_ZEROES 14 /* WRITE ZEROES is supported */ /* Legacy feature bits */ #ifndef VIRTIO_BLK_NO_LEGACY @@ -86,6 +88,39 @@ struct virtio_blk_config { /* number of vqs, only available when VIRTIO_BLK_F_MQ is set */ __u16 num_queues; + + /* the next 3 entries are guarded by VIRTIO_BLK_F_DISCARD */ + /* + * The maximum discard sectors (in 512-byte sectors) for + * one segment. + */ + __u32 max_discard_sectors; + /* + * The maximum number of discard segments in a + * discard command. + */ + __u32 max_discard_seg; + /* Discard commands must be aligned to this number of sectors. */ + __u32 discard_sector_alignment; + + /* the next 3 entries are guarded by VIRTIO_BLK_F_WRITE_ZEROES */ + /* + * The maximum number of write zeroes sectors (in 512-byte sectors) in + * one segment. + */ + __u32 max_write_zeroes_sectors; + /* + * The maximum number of segments in a write zeroes + * command. + */ + __u32 max_write_zeroes_seg; + /* + * Set if a VIRTIO_BLK_T_WRITE_ZEROES request may result in the + * deallocation of one or more of the sectors. + */ + __u8 write_zeroes_may_unmap; + + __u8 unused1[3]; } __attribute__((packed)); /* @@ -114,6 +149,12 @@ 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 +174,19 @@ struct virtio_blk_outhdr { __virtio64 sector; }; +/* Unmap this range (only valid for write zeroes command) */ +#define VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP 0x00000001 + +/* 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; + /* flags for this range */ + __virtio32 flags; +}; + #ifndef VIRTIO_BLK_NO_LEGACY struct virtio_scsi_inhdr { __virtio32 errors; -- 2.19.0.605.g01d371f741-goog
