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xen-scsiback: Convert to percpu_ida tag allocation
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This patch converts xen-scsiback to use percpu_ida tag
pre-allocation for struct vscsibk_pend descriptor, in
order to avoid fast-path struct vscsibk_pend memory
allocations.

Note by default this is currently hardcoded to 128.

(Add wrapper for handling pending_req tag failure - Juergen)
(Drop left-over se_cmd memset in scsiback_cmd_exec - Juergen)

Acked-by: Juergen Gross <jgross@suse.com>
Tested-by: Juergen Gross <jgross@suse.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
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Nicholas Bellinger committed Mar 11, 2016
1 parent cff834c commit 2dbcdf3
Showing 1 changed file with 89 additions and 78 deletions.
167 changes: 89 additions & 78 deletions drivers/xen/xen-scsiback.c
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Original file line number Diff line number Diff line change
Expand Up @@ -141,6 +141,8 @@ struct scsiback_tmr {
wait_queue_head_t tmr_wait;
};

#define VSCSI_DEFAULT_SESSION_TAGS 128

struct scsiback_nexus {
/* Pointer to TCM session for I_T Nexus */
struct se_session *tvn_se_sess;
Expand Down Expand Up @@ -190,7 +192,6 @@ module_param_named(max_buffer_pages, scsiback_max_buffer_pages, int, 0644);
MODULE_PARM_DESC(max_buffer_pages,
"Maximum number of free pages to keep in backend buffer");

static struct kmem_cache *scsiback_cachep;
static DEFINE_SPINLOCK(free_pages_lock);
static int free_pages_num;
static LIST_HEAD(scsiback_free_pages);
Expand Down Expand Up @@ -321,11 +322,11 @@ static void scsiback_free_translation_entry(struct kref *kref)
kfree(entry);
}

static void scsiback_do_resp_with_sense(char *sense_buffer, int32_t result,
uint32_t resid, struct vscsibk_pend *pending_req)
static void scsiback_send_response(struct vscsibk_info *info,
char *sense_buffer, int32_t result, uint32_t resid,
uint16_t rqid)
{
struct vscsiif_response *ring_res;
struct vscsibk_info *info = pending_req->info;
int notify;
struct scsi_sense_hdr sshdr;
unsigned long flags;
Expand All @@ -337,7 +338,7 @@ static void scsiback_do_resp_with_sense(char *sense_buffer, int32_t result,
info->ring.rsp_prod_pvt++;

ring_res->rslt = result;
ring_res->rqid = pending_req->rqid;
ring_res->rqid = rqid;

if (sense_buffer != NULL &&
scsi_normalize_sense(sense_buffer, VSCSIIF_SENSE_BUFFERSIZE,
Expand All @@ -357,6 +358,13 @@ static void scsiback_do_resp_with_sense(char *sense_buffer, int32_t result,

if (notify)
notify_remote_via_irq(info->irq);
}

static void scsiback_do_resp_with_sense(char *sense_buffer, int32_t result,
uint32_t resid, struct vscsibk_pend *pending_req)
{
scsiback_send_response(pending_req->info, sense_buffer, result,
resid, pending_req->rqid);

if (pending_req->v2p)
kref_put(&pending_req->v2p->kref,
Expand Down Expand Up @@ -388,10 +396,6 @@ static void scsiback_cmd_exec(struct vscsibk_pend *pending_req)
struct se_session *sess = pending_req->v2p->tpg->tpg_nexus->tvn_se_sess;
int rc;

memset(pending_req->sense_buffer, 0, VSCSIIF_SENSE_BUFFERSIZE);

memset(se_cmd, 0, sizeof(*se_cmd));

scsiback_get(pending_req->info);
se_cmd->tag = pending_req->rqid;
rc = target_submit_cmd_map_sgls(se_cmd, sess, pending_req->cmnd,
Expand Down Expand Up @@ -616,15 +620,13 @@ static void scsiback_device_action(struct vscsibk_pend *pending_req,
err = (se_cmd->se_tmr_req->response == TMR_FUNCTION_COMPLETE) ?
SUCCESS : FAILED;

scsiback_do_resp_with_sense(NULL, err, 0, pending_req);
transport_generic_free_cmd(&pending_req->se_cmd, 1);
return;
out:
if (tmr) {
transport_generic_free_cmd(&pending_req->se_cmd, 1);
if (tmr)
kfree(tmr);
}

scsiback_do_resp_with_sense(NULL, err, 0, pending_req);

kmem_cache_free(scsiback_cachep, pending_req);
}

/*
Expand Down Expand Up @@ -653,49 +655,78 @@ static struct v2p_entry *scsiback_do_translation(struct vscsibk_info *info,
return entry;
}

static int prepare_pending_reqs(struct vscsibk_info *info,
struct vscsiif_request *ring_req,
struct vscsibk_pend *pending_req)
static struct vscsibk_pend *scsiback_get_pend_req(struct vscsiif_back_ring *ring,
struct v2p_entry *v2p)
{
struct scsiback_tpg *tpg = v2p->tpg;
struct scsiback_nexus *nexus = tpg->tpg_nexus;
struct se_session *se_sess = nexus->tvn_se_sess;
struct vscsibk_pend *req;
int tag, i;

tag = percpu_ida_alloc(&se_sess->sess_tag_pool, TASK_RUNNING);
if (tag < 0) {
pr_err("Unable to obtain tag for vscsiif_request\n");
return ERR_PTR(-ENOMEM);
}

req = &((struct vscsibk_pend *)se_sess->sess_cmd_map)[tag];
memset(req, 0, sizeof(*req));
req->se_cmd.map_tag = tag;

for (i = 0; i < VSCSI_MAX_GRANTS; i++)
req->grant_handles[i] = SCSIBACK_INVALID_HANDLE;

return req;
}

static struct vscsibk_pend *prepare_pending_reqs(struct vscsibk_info *info,
struct vscsiif_back_ring *ring,
struct vscsiif_request *ring_req)
{
struct vscsibk_pend *pending_req;
struct v2p_entry *v2p;
struct ids_tuple vir;

pending_req->rqid = ring_req->rqid;
pending_req->info = info;
/* request range check from frontend */
if ((ring_req->sc_data_direction != DMA_BIDIRECTIONAL) &&
(ring_req->sc_data_direction != DMA_TO_DEVICE) &&
(ring_req->sc_data_direction != DMA_FROM_DEVICE) &&
(ring_req->sc_data_direction != DMA_NONE)) {
pr_debug("invalid parameter data_dir = %d\n",
ring_req->sc_data_direction);
return ERR_PTR(-EINVAL);
}
if (ring_req->cmd_len > VSCSIIF_MAX_COMMAND_SIZE) {
pr_debug("invalid parameter cmd_len = %d\n",
ring_req->cmd_len);
return ERR_PTR(-EINVAL);
}

vir.chn = ring_req->channel;
vir.tgt = ring_req->id;
vir.lun = ring_req->lun;

v2p = scsiback_do_translation(info, &vir);
if (!v2p) {
pending_req->v2p = NULL;
pr_debug("the v2p of (chn:%d, tgt:%d, lun:%d) doesn't exist.\n",
vir.chn, vir.tgt, vir.lun);
return -ENODEV;
vir.chn, vir.tgt, vir.lun);
return ERR_PTR(-ENODEV);
}
pending_req->v2p = v2p;

/* request range check from frontend */
pending_req->sc_data_direction = ring_req->sc_data_direction;
if ((pending_req->sc_data_direction != DMA_BIDIRECTIONAL) &&
(pending_req->sc_data_direction != DMA_TO_DEVICE) &&
(pending_req->sc_data_direction != DMA_FROM_DEVICE) &&
(pending_req->sc_data_direction != DMA_NONE)) {
pr_debug("invalid parameter data_dir = %d\n",
pending_req->sc_data_direction);
return -EINVAL;
pending_req = scsiback_get_pend_req(ring, v2p);
if (IS_ERR(pending_req)) {
kref_put(&v2p->kref, scsiback_free_translation_entry);
return ERR_PTR(-ENOMEM);
}

pending_req->rqid = ring_req->rqid;
pending_req->info = info;
pending_req->v2p = v2p;
pending_req->sc_data_direction = ring_req->sc_data_direction;
pending_req->cmd_len = ring_req->cmd_len;
if (pending_req->cmd_len > VSCSIIF_MAX_COMMAND_SIZE) {
pr_debug("invalid parameter cmd_len = %d\n",
pending_req->cmd_len);
return -EINVAL;
}
memcpy(pending_req->cmnd, ring_req->cmnd, pending_req->cmd_len);

return 0;
return pending_req;
}

static int scsiback_do_cmd_fn(struct vscsibk_info *info)
Expand All @@ -704,7 +735,7 @@ static int scsiback_do_cmd_fn(struct vscsibk_info *info)
struct vscsiif_request ring_req;
struct vscsibk_pend *pending_req;
RING_IDX rc, rp;
int err, more_to_do;
int more_to_do;
uint32_t result;

rc = ring->req_cons;
Expand All @@ -722,26 +753,22 @@ static int scsiback_do_cmd_fn(struct vscsibk_info *info)
while ((rc != rp)) {
if (RING_REQUEST_CONS_OVERFLOW(ring, rc))
break;
pending_req = kmem_cache_alloc(scsiback_cachep, GFP_KERNEL);
if (!pending_req)
return 1;

RING_COPY_REQUEST(ring, rc, &ring_req);
ring->req_cons = ++rc;

err = prepare_pending_reqs(info, &ring_req, pending_req);
if (err) {
switch (err) {
pending_req = prepare_pending_reqs(info, ring, &ring_req);
if (IS_ERR(pending_req)) {
switch (PTR_ERR(pending_req)) {
case -ENODEV:
result = DID_NO_CONNECT;
break;
default:
result = DRIVER_ERROR;
break;
}
scsiback_do_resp_with_sense(NULL, result << 24, 0,
pending_req);
kmem_cache_free(scsiback_cachep, pending_req);
scsiback_send_response(info, NULL, result << 24, 0,
ring_req.rqid);
return 1;
}

Expand All @@ -750,8 +777,8 @@ static int scsiback_do_cmd_fn(struct vscsibk_info *info)
if (scsiback_gnttab_data_map(&ring_req, pending_req)) {
scsiback_fast_flush_area(pending_req);
scsiback_do_resp_with_sense(NULL,
DRIVER_ERROR << 24, 0, pending_req);
kmem_cache_free(scsiback_cachep, pending_req);
DRIVER_ERROR << 24, 0, pending_req);
transport_generic_free_cmd(&pending_req->se_cmd, 0);
} else {
scsiback_cmd_exec(pending_req);
}
Expand All @@ -765,9 +792,9 @@ static int scsiback_do_cmd_fn(struct vscsibk_info *info)
break;
default:
pr_err_ratelimited("invalid request\n");
scsiback_do_resp_with_sense(NULL, DRIVER_ERROR << 24,
0, pending_req);
kmem_cache_free(scsiback_cachep, pending_req);
scsiback_do_resp_with_sense(NULL, DRIVER_ERROR << 24, 0,
pending_req);
transport_generic_free_cmd(&pending_req->se_cmd, 0);
break;
}

Expand Down Expand Up @@ -1355,10 +1382,9 @@ static int scsiback_check_stop_free(struct se_cmd *se_cmd)

static void scsiback_release_cmd(struct se_cmd *se_cmd)
{
struct vscsibk_pend *pending_req = container_of(se_cmd,
struct vscsibk_pend, se_cmd);
struct se_session *se_sess = se_cmd->se_sess;

kmem_cache_free(scsiback_cachep, pending_req);
percpu_ida_free(&se_sess->sess_tag_pool, se_cmd->map_tag);
}

static int scsiback_shutdown_session(struct se_session *se_sess)
Expand Down Expand Up @@ -1511,7 +1537,9 @@ static int scsiback_make_nexus(struct scsiback_tpg *tpg,
goto out_unlock;
}

tv_nexus->tvn_se_sess = target_alloc_session(&tpg->se_tpg, 0, 0,
tv_nexus->tvn_se_sess = target_alloc_session(&tpg->se_tpg,
VSCSI_DEFAULT_SESSION_TAGS,
sizeof(struct vscsibk_pend),
TARGET_PROT_NORMAL, name,
tv_nexus, scsiback_alloc_sess_cb);
if (IS_ERR(tv_nexus->tvn_se_sess)) {
Expand Down Expand Up @@ -1840,16 +1868,6 @@ static struct xenbus_driver scsiback_driver = {
.otherend_changed = scsiback_frontend_changed
};

static void scsiback_init_pend(void *p)
{
struct vscsibk_pend *pend = p;
int i;

memset(pend, 0, sizeof(*pend));
for (i = 0; i < VSCSI_MAX_GRANTS; i++)
pend->grant_handles[i] = SCSIBACK_INVALID_HANDLE;
}

static int __init scsiback_init(void)
{
int ret;
Expand All @@ -1860,14 +1878,9 @@ static int __init scsiback_init(void)
pr_debug("xen-pvscsi: fabric module %s on %s/%s on "UTS_RELEASE"\n",
VSCSI_VERSION, utsname()->sysname, utsname()->machine);

scsiback_cachep = kmem_cache_create("vscsiif_cache",
sizeof(struct vscsibk_pend), 0, 0, scsiback_init_pend);
if (!scsiback_cachep)
return -ENOMEM;

ret = xenbus_register_backend(&scsiback_driver);
if (ret)
goto out_cache_destroy;
goto out;

ret = target_register_template(&scsiback_ops);
if (ret)
Expand All @@ -1877,8 +1890,7 @@ static int __init scsiback_init(void)

out_unregister_xenbus:
xenbus_unregister_driver(&scsiback_driver);
out_cache_destroy:
kmem_cache_destroy(scsiback_cachep);
out:
pr_err("%s: error %d\n", __func__, ret);
return ret;
}
Expand All @@ -1894,7 +1906,6 @@ static void __exit scsiback_exit(void)
}
target_unregister_template(&scsiback_ops);
xenbus_unregister_driver(&scsiback_driver);
kmem_cache_destroy(scsiback_cachep);
}

module_init(scsiback_init);
Expand Down

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