The support is added via the new SGV4_FLAG_HIPRI command flag which
causes REQ_HIPRI to be set on the request. Before waiting on an
inflight request, it is checked to see if it has SGV4_FLAG_HIPRI,
and if so blk_poll() is called instead of the wait. In situations
where only the file descriptor is known (e.g. sg_poll() and
ioctl(SG_GET_NUM_WAITING)) all inflight requests associated with
the file descriptor that have SGV4_FLAG_HIPRI set, have blk_poll()
called on them.
It is important to know blk_execute_rq_nowait() has finished before
sending blk_poll() on that request. The SG_RS_INFLIGHT state is set
just before blk_execute_rq_nowait() is called so a new bit setting
SG_FRQ_ISSUED has been added that is set just after that calls
returns.
Note that the implementation of blk_poll() calls mq_poll() in the
LLD associated with the request. Then for any request found to be
ready, blk_poll() invokes the scsi_done() callback. When blk_poll()
returns > 0 , sg_rq_end_io() may have been called on the given
request. If so the given request will be in await_rcv state.
Signed-off-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
---
drivers/scsi/sg.c | 108 ++++++++++++++++++++++++++++++++++++++---
include/uapi/scsi/sg.h | 1 +
2 files changed, 103 insertions(+), 6 deletions(-)
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 0982cb031be9..19aafd8e23f1 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -116,12 +116,14 @@ enum sg_rq_state { /* N.B. sg_rq_state_arr assumes
SG_RS_AWAIT_RCV==2 */
#define SG_FRQ_RECEIVING 7 /* guard against multiple receivers */
#define SG_FRQ_FOR_MMAP 8 /* request needs PAGE_SIZE elements */
#define SG_FRQ_COUNT_ACTIVE 9 /* sfp->submitted + waiting active */
+#define SG_FRQ_ISSUED 10 /* blk_execute_rq_nowait() finished */
/* Bit positions (flags) for sg_fd::ffd_bm bitmask follow */
#define SG_FFD_FORCE_PACKID 0 /* receive only given pack_id/tag */
#define SG_FFD_CMD_Q 1 /* clear: only 1 active req per fd */
#define SG_FFD_KEEP_ORPHAN 2 /* policy for this fd */
-#define SG_FFD_Q_AT_TAIL 3 /* set: queue reqs at tail of blk q */
+#define SG_FFD_HIPRI_SEEN 3 /* could have HIPRI requests active */
+#define SG_FFD_Q_AT_TAIL 4 /* set: queue reqs at tail of blk q */
/* Bit positions (flags) for sg_device::fdev_bm bitmask follow */
#define SG_FDEV_EXCLUDE 0 /* have fd open with O_EXCL */
@@ -210,6 +212,7 @@ struct sg_request { /* active SCSI command or inactive
request */
int sense_len; /* actual sense buffer length (data-in) */
atomic_t rq_st; /* request state, holds a enum sg_rq_state */
u8 cmd_opcode; /* first byte of SCSI cdb */
+ blk_qc_t cookie; /* ids 1 or more queues for blk_poll() */
u64 start_ns; /* starting point of command duration calc */
unsigned long frq_bm[1]; /* see SG_FRQ_* defines above */
u8 *sense_bp; /* mempool alloc-ed sense buffer, as needed */
@@ -299,6 +302,9 @@ static struct sg_device *sg_get_dev(int min_dev);
static void sg_device_destroy(struct kref *kref);
static struct sg_request *sg_mk_srp_sgat(struct sg_fd *sfp, bool first,
int db_len);
+static int sg_sfp_blk_poll(struct sg_fd *sfp, int loop_count);
+static int sg_srp_q_blk_poll(struct sg_request *srp, struct request_queue *q,
+ int loop_count);
#if IS_ENABLED(CONFIG_SCSI_LOGGING) && IS_ENABLED(SG_DEBUG)
static const char *sg_rq_st_str(enum sg_rq_state rq_st, bool long_str);
#endif
@@ -1008,6 +1014,7 @@ sg_execute_cmd(struct sg_fd *sfp, struct sg_request *srp)
{
bool at_head, is_v4h, sync;
struct sg_device *sdp = sfp->parentdp;
+ struct request *rqq = READ_ONCE(srp->rqq);
is_v4h = test_bit(SG_FRQ_IS_V4I, srp->frq_bm);
sync = test_bit(SG_FRQ_SYNC_INVOC, srp->frq_bm);
@@ -1031,7 +1038,12 @@ sg_execute_cmd(struct sg_fd *sfp, struct sg_request *srp)
atomic_inc(&sfp->submitted);
set_bit(SG_FRQ_COUNT_ACTIVE, srp->frq_bm);
}
- blk_execute_rq_nowait(sdp->disk, READ_ONCE(srp->rqq), (int)at_head,
sg_rq_end_io);
+ if (srp->rq_flags & SGV4_FLAG_HIPRI) {
+ rqq->cmd_flags |= REQ_HIPRI;
+ srp->cookie = request_to_qc_t(rqq->mq_hctx, rqq);
+ }
+ blk_execute_rq_nowait(sdp->disk, rqq, (int)at_head, sg_rq_end_io);
+ set_bit(SG_FRQ_ISSUED, srp->frq_bm);
}
/*
@@ -1693,6 +1705,13 @@ sg_wait_event_srp(struct file *filp, struct sg_fd *sfp,
void __user *p,
if (atomic_read(&srp->rq_st) != SG_RS_INFLIGHT)
goto skip_wait; /* and skip _acquire() */
+ if (srp->rq_flags & SGV4_FLAG_HIPRI) {
+ /* call blk_poll(), spinning till found */
+ res = sg_srp_q_blk_poll(srp, sdp->device->request_queue, -1);
+ if (res != -ENODATA && unlikely(res < 0))
+ return res;
+ goto skip_wait;
+ }
SG_LOG(3, sfp, "%s: about to wait_event...()\n", __func__);
/* usually will be woken up by sg_rq_end_io() callback */
res = wait_event_interruptible(sfp->read_wait,
@@ -2019,6 +2038,8 @@ sg_ioctl_common(struct file *filp, struct sg_device
*sdp, struct sg_fd *sfp,
SG_LOG(3, sfp, "%s: SG_GET_PACK_ID=%d\n", __func__, val);
return put_user(val, ip);
case SG_GET_NUM_WAITING:
+ if (test_bit(SG_FFD_HIPRI_SEEN, sfp->ffd_bm))
+ sg_sfp_blk_poll(sfp, 0); /* LLD may have some ready */
val = atomic_read(&sfp->waiting);
if (val)
return put_user(val, ip);
@@ -2228,6 +2249,69 @@ sg_compat_ioctl(struct file *filp, unsigned int cmd_in,
unsigned long arg)
}
#endif
+/*
+ * If the sg_request object is not inflight, return -ENODATA. This function
+ * returns 1 if the given object was in inflight state and is in await_rcv
+ * state after blk_poll() returns 1 or more. If blk_poll() fails, then that
+ * (negative) value is returned. Otherwise returns 0. Note that blk_poll()
+ * may complete unrelated requests that share the same q and cookie.
+ */
+static int
+sg_srp_q_blk_poll(struct sg_request *srp, struct request_queue *q, int
loop_count)
+{
+ int k, n, num;
+
+ num = (loop_count < 1) ? 1 : loop_count;
+ for (k = 0; k < num; ++k) {
+ if (atomic_read(&srp->rq_st) != SG_RS_INFLIGHT)
+ return -ENODATA;
+ n = blk_poll(q, srp->cookie, loop_count < 0 /* spin if negative */);
+ if (n > 0)
+ return atomic_read(&srp->rq_st) == SG_RS_AWAIT_RCV;
