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IB/srp: Implement SRP_CRED_REQ and SRP_AER_REQ
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This patch adds support for SRP_CRED_REQ to avoid a lockup by targets
that use that mechanism to return credits to the initiator. This
prevents a lockup observed in the field where we would never add the
credits from the SRP_CRED_REQ to our current count, and would therefore
never send another command to the target.

Minimal support for SRP_AER_REQ is also added, as these messages can
also be used to convey additional credits to the initiator.

Based upon extensive debugging and code by Bart Van Assche and a bug
report by Chris Worley.

Signed-off-by: David Dillow <dillowda@ornl.gov>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
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David Dillow authored and Roland Dreier committed Oct 23, 2010
1 parent dd5e6e3 commit bb12588
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Showing 3 changed files with 141 additions and 10 deletions.
105 changes: 98 additions & 7 deletions drivers/infiniband/ulp/srp/ib_srp.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -83,6 +83,10 @@ static void srp_remove_one(struct ib_device *device);
static void srp_recv_completion(struct ib_cq *cq, void *target_ptr);
static void srp_send_completion(struct ib_cq *cq, void *target_ptr);
static int srp_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event);
static struct srp_iu *__srp_get_tx_iu(struct srp_target_port *target,
enum srp_iu_type iu_type);
static int __srp_post_send(struct srp_target_port *target,
struct srp_iu *iu, int len);

static struct scsi_transport_template *ib_srp_transport_template;

Expand Down Expand Up @@ -896,6 +900,71 @@ static void srp_process_rsp(struct srp_target_port *target, struct srp_rsp *rsp)
spin_unlock_irqrestore(target->scsi_host->host_lock, flags);
}

static int srp_response_common(struct srp_target_port *target, s32 req_delta,
void *rsp, int len)
{
struct ib_device *dev;
unsigned long flags;
struct srp_iu *iu;
int err = 1;

dev = target->srp_host->srp_dev->dev;

spin_lock_irqsave(target->scsi_host->host_lock, flags);
target->req_lim += req_delta;

iu = __srp_get_tx_iu(target, SRP_IU_RSP);
if (!iu) {
shost_printk(KERN_ERR, target->scsi_host, PFX
"no IU available to send response\n");
goto out;
}

ib_dma_sync_single_for_cpu(dev, iu->dma, len, DMA_TO_DEVICE);
memcpy(iu->buf, rsp, len);
ib_dma_sync_single_for_device(dev, iu->dma, len, DMA_TO_DEVICE);

err = __srp_post_send(target, iu, len);
if (err)
shost_printk(KERN_ERR, target->scsi_host, PFX
"unable to post response: %d\n", err);

out:
spin_unlock_irqrestore(target->scsi_host->host_lock, flags);
return err;
}

static void srp_process_cred_req(struct srp_target_port *target,
struct srp_cred_req *req)
{
struct srp_cred_rsp rsp = {
.opcode = SRP_CRED_RSP,
.tag = req->tag,
};
s32 delta = be32_to_cpu(req->req_lim_delta);

if (srp_response_common(target, delta, &rsp, sizeof rsp))
shost_printk(KERN_ERR, target->scsi_host, PFX
"problems processing SRP_CRED_REQ\n");
}

static void srp_process_aer_req(struct srp_target_port *target,
struct srp_aer_req *req)
{
struct srp_aer_rsp rsp = {
.opcode = SRP_AER_RSP,
.tag = req->tag,
};
s32 delta = be32_to_cpu(req->req_lim_delta);

shost_printk(KERN_ERR, target->scsi_host, PFX
"ignoring AER for LUN %llu\n", be64_to_cpu(req->lun));

if (srp_response_common(target, delta, &rsp, sizeof rsp))
shost_printk(KERN_ERR, target->scsi_host, PFX
"problems processing SRP_AER_REQ\n");
}

static void srp_handle_recv(struct srp_target_port *target, struct ib_wc *wc)
{
struct ib_device *dev;
Expand Down Expand Up @@ -923,6 +992,14 @@ static void srp_handle_recv(struct srp_target_port *target, struct ib_wc *wc)
srp_process_rsp(target, iu->buf);
break;

case SRP_CRED_REQ:
srp_process_cred_req(target, iu->buf);
break;

case SRP_AER_REQ:
srp_process_aer_req(target, iu->buf);
break;

case SRP_T_LOGOUT:
/* XXX Handle target logout */
shost_printk(KERN_WARNING, target->scsi_host,
Expand Down Expand Up @@ -985,23 +1062,36 @@ static void srp_send_completion(struct ib_cq *cq, void *target_ptr)
* Must be called with target->scsi_host->host_lock held to protect
* req_lim and tx_head. Lock cannot be dropped between call here and
* call to __srp_post_send().
*
* Note:
* An upper limit for the number of allocated information units for each
* request type is:
* - SRP_IU_CMD: SRP_CMD_SQ_SIZE, since the SCSI mid-layer never queues
* more than Scsi_Host.can_queue requests.
* - SRP_IU_TSK_MGMT: SRP_TSK_MGMT_SQ_SIZE.
* - SRP_IU_RSP: 1, since a conforming SRP target never sends more than
* one unanswered SRP request to an initiator.
*/
static struct srp_iu *__srp_get_tx_iu(struct srp_target_port *target,
enum srp_request_type req_type)
enum srp_iu_type iu_type)
{
s32 rsv = (req_type == SRP_REQ_TASK_MGMT) ? 0 : SRP_TSK_MGMT_SQ_SIZE;
s32 rsv = (iu_type == SRP_IU_TSK_MGMT) ? 0 : SRP_TSK_MGMT_SQ_SIZE;
struct srp_iu *iu;

srp_send_completion(target->send_cq, target);

if (target->tx_head - target->tx_tail >= SRP_SQ_SIZE)
return NULL;

if (target->req_lim <= rsv) {
/* Initiator responses to target requests do not consume credits */
if (target->req_lim <= rsv && iu_type != SRP_IU_RSP) {
++target->zero_req_lim;
return NULL;
}

return target->tx_ring[target->tx_head & SRP_SQ_MASK];
iu = target->tx_ring[target->tx_head & SRP_SQ_MASK];
iu->type = iu_type;
return iu;
}

/*
Expand Down Expand Up @@ -1030,7 +1120,8 @@ static int __srp_post_send(struct srp_target_port *target,

if (!ret) {
++target->tx_head;
--target->req_lim;
if (iu->type != SRP_IU_RSP)
--target->req_lim;
}

return ret;
Expand All @@ -1056,7 +1147,7 @@ static int srp_queuecommand(struct scsi_cmnd *scmnd,
return 0;
}

iu = __srp_get_tx_iu(target, SRP_REQ_NORMAL);
iu = __srp_get_tx_iu(target, SRP_IU_CMD);
if (!iu)
goto err;

Expand Down Expand Up @@ -1363,7 +1454,7 @@ static int srp_send_tsk_mgmt(struct srp_target_port *target,

init_completion(&req->done);

iu = __srp_get_tx_iu(target, SRP_REQ_TASK_MGMT);
iu = __srp_get_tx_iu(target, SRP_IU_TSK_MGMT);
if (!iu)
goto out;

Expand Down
8 changes: 5 additions & 3 deletions drivers/infiniband/ulp/srp/ib_srp.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -82,9 +82,10 @@ enum srp_target_state {
SRP_TARGET_REMOVED
};

enum srp_request_type {
SRP_REQ_NORMAL,
SRP_REQ_TASK_MGMT,
enum srp_iu_type {
SRP_IU_CMD,
SRP_IU_TSK_MGMT,
SRP_IU_RSP,
};

struct srp_device {
Expand Down Expand Up @@ -171,6 +172,7 @@ struct srp_iu {
void *buf;
size_t size;
enum dma_data_direction direction;
enum srp_iu_type type;
};

#endif /* IB_SRP_H */
38 changes: 38 additions & 0 deletions include/scsi/srp.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -239,4 +239,42 @@ struct srp_rsp {
u8 data[0];
} __attribute__((packed));

struct srp_cred_req {
u8 opcode;
u8 sol_not;
u8 reserved[2];
__be32 req_lim_delta;
u64 tag;
};

struct srp_cred_rsp {
u8 opcode;
u8 reserved[7];
u64 tag;
};

/*
* The SRP spec defines the fixed portion of the AER_REQ structure to be
* 36 bytes, so it needs to be packed to avoid having it padded to 40 bytes
* on 64-bit architectures.
*/
struct srp_aer_req {
u8 opcode;
u8 sol_not;
u8 reserved[2];
__be32 req_lim_delta;
u64 tag;
u32 reserved2;
__be64 lun;
__be32 sense_data_len;
u32 reserved3;
u8 sense_data[0];
} __attribute__((packed));

struct srp_aer_rsp {
u8 opcode;
u8 reserved[7];
u64 tag;
};

#endif /* SCSI_SRP_H */

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