[PATCH RFC v2 07/24] virtio_scsi: use reserved commands for TMF

From: John Garry
Date: Tue Mar 10 2020 - 12:31:02 EST

From: Hannes Reinecke <hare@xxxxxxxx>

Set two commands aside for TMF, and use reserved commands to issue
TMFs. With that we can drop the TMF memory pool.

Signed-off-by: Hannes Reinecke <hare@xxxxxxxx>
---
drivers/scsi/virtio_scsi.c | 107 +++++++++++++++----------------------
1 file changed, 43 insertions(+), 64 deletions(-)

diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index bfec84aacd90..05c772be2c9c 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -35,10 +35,10 @@
#define VIRTIO_SCSI_MEMPOOL_SZ 64
#define VIRTIO_SCSI_EVENT_LEN 8
#define VIRTIO_SCSI_VQ_BASE 2
+#define VIRTIO_SCSI_RESERVED_CMDS 2

/* Command queue element */
struct virtio_scsi_cmd {
- struct scsi_cmnd *sc;
struct completion *comp;
union {
struct virtio_scsi_cmd_req cmd;
@@ -86,9 +86,6 @@ struct virtio_scsi {
struct virtio_scsi_vq req_vqs[];
};

-static struct kmem_cache *virtscsi_cmd_cache;
-static mempool_t *virtscsi_cmd_pool;
-
static inline struct Scsi_Host *virtio_scsi_host(struct virtio_device *vdev)
{
return vdev->priv;
@@ -108,7 +105,7 @@ static void virtscsi_compute_resid(struct scsi_cmnd *sc, u32 resid)
static void virtscsi_complete_cmd(struct virtio_scsi *vscsi, void *buf)
{
struct virtio_scsi_cmd *cmd = buf;
- struct scsi_cmnd *sc = cmd->sc;
+ struct scsi_cmnd *sc = scsi_cmd_from_priv(cmd);
struct virtio_scsi_cmd_resp *resp = &cmd->resp.cmd;

dev_dbg(&sc->device->sdev_gendev,
@@ -406,7 +403,7 @@ static int __virtscsi_add_cmd(struct virtqueue *vq,
struct virtio_scsi_cmd *cmd,
size_t req_size, size_t resp_size)
{
- struct scsi_cmnd *sc = cmd->sc;
+ struct scsi_cmnd *sc = scsi_cmd_from_priv(cmd);
struct scatterlist *sgs[6], req, resp;
struct sg_table *out, *in;
unsigned out_num = 0, in_num = 0;
@@ -557,8 +554,6 @@ static int virtscsi_queuecommand(struct Scsi_Host *shost,
dev_dbg(&sc->device->sdev_gendev,
"cmd %p CDB: %#02x\n", sc, sc->cmnd[0]);

- cmd->sc = sc;
-
BUG_ON(sc->cmd_len > VIRTIO_SCSI_CDB_SIZE);

#ifdef CONFIG_BLK_DEV_INTEGRITY
@@ -590,17 +585,17 @@ static int virtscsi_queuecommand(struct Scsi_Host *shost,
static int virtscsi_tmf(struct virtio_scsi *vscsi, struct virtio_scsi_cmd *cmd)
{
DECLARE_COMPLETION_ONSTACK(comp);
- int ret = FAILED;

cmd->comp = &comp;
+
if (virtscsi_add_cmd(&vscsi->ctrl_vq, cmd,
sizeof cmd->req.tmf, sizeof cmd->resp.tmf, true) < 0)
- goto out;
+ return FAILED;

wait_for_completion(&comp);
if (cmd->resp.tmf.response == VIRTIO_SCSI_S_OK ||
cmd->resp.tmf.response == VIRTIO_SCSI_S_FUNCTION_SUCCEEDED)
- ret = SUCCESS;
+ return SUCCESS;

/*
* The spec guarantees that all requests related to the TMF have
@@ -613,33 +608,37 @@ static int virtscsi_tmf(struct virtio_scsi *vscsi, struct virtio_scsi_cmd *cmd)
* REQ_ATOM_COMPLETE has been set.
*/
virtscsi_poll_requests(vscsi);
-
-out:
- mempool_free(cmd, virtscsi_cmd_pool);
- return ret;
+ return FAILED;
}

static int virtscsi_device_reset(struct scsi_cmnd *sc)
{
+ struct scsi_device *sdev = sc->device;
+ struct Scsi_Host *shost = sdev->host;
+ struct scsi_cmnd *reset_sc;
struct virtio_scsi *vscsi = shost_priv(sc->device->host);
struct virtio_scsi_cmd *cmd;
+ int rc;

- sdev_printk(KERN_INFO, sc->device, "device reset\n");
- cmd = mempool_alloc(virtscsi_cmd_pool, GFP_NOIO);
- if (!cmd)
+ sdev_printk(KERN_INFO, sdev, "device reset\n");
+ reset_sc = scsi_get_reserved_cmd(shost);
+ if (!reset_sc)
return FAILED;
-
+ cmd = scsi_cmd_priv(reset_sc);
memset(cmd, 0, sizeof(*cmd));
cmd->req.tmf = (struct virtio_scsi_ctrl_tmf_req){
.type = VIRTIO_SCSI_T_TMF,
.subtype = cpu_to_virtio32(vscsi->vdev,
VIRTIO_SCSI_T_TMF_LOGICAL_UNIT_RESET),
.lun[0] = 1,
- .lun[1] = sc->device->id,
- .lun[2] = (sc->device->lun >> 8) | 0x40,
- .lun[3] = sc->device->lun & 0xff,
+ .lun[1] = sdev->id,
+ .lun[2] = (sdev->lun >> 8) | 0x40,
+ .lun[3] = sdev->lun & 0xff,
};
- return virtscsi_tmf(vscsi, cmd);
+ rc = virtscsi_tmf(vscsi, cmd);
+ scsi_put_reserved_cmd(reset_sc);
+
+ return rc;
}

static int virtscsi_device_alloc(struct scsi_device *sdevice)
@@ -679,25 +678,32 @@ static int virtscsi_change_queue_depth(struct scsi_device *sdev, int qdepth)

static int virtscsi_abort(struct scsi_cmnd *sc)
{
- struct virtio_scsi *vscsi = shost_priv(sc->device->host);
+ struct scsi_device *sdev = sc->device;
+ struct Scsi_Host *shost = sdev->host;
+ struct scsi_cmnd *reset_sc;
+ struct virtio_scsi *vscsi = shost_priv(sdev->host);
struct virtio_scsi_cmd *cmd;
+ int rc;

scmd_printk(KERN_INFO, sc, "abort\n");
- cmd = mempool_alloc(virtscsi_cmd_pool, GFP_NOIO);
- if (!cmd)
+ reset_sc = scsi_get_reserved_cmd(shost);
+ if (!reset_sc)
return FAILED;
+ cmd = scsi_cmd_priv(reset_sc);

memset(cmd, 0, sizeof(*cmd));
cmd->req.tmf = (struct virtio_scsi_ctrl_tmf_req){
.type = VIRTIO_SCSI_T_TMF,
.subtype = VIRTIO_SCSI_T_TMF_ABORT_TASK,
.lun[0] = 1,
- .lun[1] = sc->device->id,
- .lun[2] = (sc->device->lun >> 8) | 0x40,
- .lun[3] = sc->device->lun & 0xff,
+ .lun[1] = sdev->id,
+ .lun[2] = (sdev->lun >> 8) | 0x40,
+ .lun[3] = sdev->lun & 0xff,
.tag = cpu_to_virtio64(vscsi->vdev, (unsigned long)sc),
};
- return virtscsi_tmf(vscsi, cmd);
+ rc = virtscsi_tmf(vscsi, cmd);
+ scsi_put_reserved_cmd(reset_sc);
+ return rc;
}

static int virtscsi_map_queues(struct Scsi_Host *shost)
@@ -866,6 +872,11 @@ static int virtscsi_probe(struct virtio_device *vdev)
goto virtscsi_init_failed;

shost->can_queue = virtqueue_get_vring_size(vscsi->req_vqs[0].vq);
+ shost->can_queue -= VIRTIO_SCSI_RESERVED_CMDS;
+ if (shost->can_queue <= 0) {
+ err = -ENOMEM;
+ goto scsi_add_host_failed;
+ }

cmd_per_lun = virtscsi_config_get(vdev, cmd_per_lun) ?: 1;
shost->cmd_per_lun = min_t(u32, cmd_per_lun, shost->can_queue);
@@ -879,6 +890,7 @@ static int virtscsi_probe(struct virtio_device *vdev)
shost->max_channel = 0;
shost->max_cmd_len = VIRTIO_SCSI_CDB_SIZE;
shost->nr_hw_queues = num_queues;
+ shost->nr_reserved_cmds = VIRTIO_SCSI_RESERVED_CMDS;

#ifdef CONFIG_BLK_DEV_INTEGRITY
if (virtio_has_feature(vdev, VIRTIO_SCSI_F_T10_PI)) {
@@ -980,45 +992,12 @@ static struct virtio_driver virtio_scsi_driver = {

static int __init init(void)
{
- int ret = -ENOMEM;
-
- virtscsi_cmd_cache = KMEM_CACHE(virtio_scsi_cmd, 0);
- if (!virtscsi_cmd_cache) {
- pr_err("kmem_cache_create() for virtscsi_cmd_cache failed\n");
- goto error;
- }
-
-
- virtscsi_cmd_pool =
- mempool_create_slab_pool(VIRTIO_SCSI_MEMPOOL_SZ,
- virtscsi_cmd_cache);
- if (!virtscsi_cmd_pool) {
- pr_err("mempool_create() for virtscsi_cmd_pool failed\n");
- goto error;
- }
- ret = register_virtio_driver(&virtio_scsi_driver);
- if (ret < 0)
- goto error;
-
- return 0;
-
-error:
- if (virtscsi_cmd_pool) {
- mempool_destroy(virtscsi_cmd_pool);
- virtscsi_cmd_pool = NULL;
- }
- if (virtscsi_cmd_cache) {
- kmem_cache_destroy(virtscsi_cmd_cache);
- virtscsi_cmd_cache = NULL;
- }
- return ret;
+ return register_virtio_driver(&virtio_scsi_driver);
}

static void __exit fini(void)
{
unregister_virtio_driver(&virtio_scsi_driver);
- mempool_destroy(virtscsi_cmd_pool);
- kmem_cache_destroy(virtscsi_cmd_cache);
}
module_init(init);
module_exit(fini);
--
2.17.1