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 sg_poll()
called on them.
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. So this means
if blk_poll() returns 1 then sg_rq_end_io() has already been
called for the polled request.
Signed-off-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
---
drivers/scsi/sg.c | 87 ++++++++++++++++++++++++++++++++++++++++--
include/uapi/scsi/sg.h | 1 +
2 files changed, 84 insertions(+), 4 deletions(-)
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index ad97f0756a9c..b396d3fb7bb7 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -123,6 +123,7 @@ enum sg_rq_state { /* N.B. sg_rq_state_arr
assumes SG_RS_AWAIT_RCV==2 */
#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_MMAP_CALLED 3 /* mmap(2) system call made on
fd */
+#define SG_FFD_HIPRI_SEEN 4 /* could have HIPRI requests
active */
#define SG_FFD_Q_AT_TAIL 5 /* set: queue reqs at tail of blk
q */
/* Bit positions (flags) for sg_device::fdev_bm bitmask follow */
@@ -301,6 +302,8 @@ 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_blk_poll(struct sg_request *srp, 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
@@ -1033,6 +1036,8 @@ sg_execute_cmd(struct sg_fd *sfp, struct
sg_request *srp)
atomic_inc(&sfp->submitted);
set_bit(SG_FRQ_COUNT_ACTIVE, srp->frq_bm);
}
+ if (srp->rq_flags & SGV4_FLAG_HIPRI)
+ srp->rq->cmd_flags |= REQ_HIPRI;
blk_execute_rq_nowait(sdp->device->request_queue, sdp->disk,
srp->rq, (int)at_head, sg_rq_end_io);
}
@@ -1705,6 +1710,12 @@ 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) {
+ res = sg_srp_blk_poll(srp, -1); /* spin till found */
+ if (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,
@@ -2032,6 +2043,8 @@ 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
push */
val = atomic_read(&sfp->waiting);
if (val)
return put_user(val, ip);
@@ -2241,6 +2254,59 @@ sg_compat_ioctl(struct file *filp, unsigned
int cmd_in, unsigned long arg)
}
#endif
+static int
+sg_srp_q_blk_poll(struct sg_request *srp, struct request_queue *q,
int loop_count)
+{
+ int k, n, num;
+ blk_qc_t cookie = request_to_qc_t(srp->rq->mq_hctx, srp->rq);
+
+ num = (loop_count < 1) ? 1 : loop_count;
+ for (k = 0; k < num; ++k) {
+ n = blk_poll(q, cookie, loop_count < 0 /* spin if negative */);
+ if (n != 0)
+ return n;
+ }
+ return 0;
+}
+
+/*
+ * Check all requests on this sfp that are both inflight and HIPRI.
That check involves calling
+ * blk_poll(spin<-false) loop_count times. If loop_count is 0 then
call blk_poll once.
+ * If loop_count is negative then call blk_poll(spin<-true)) once
for each request.
+ * Returns number found (could be 0) or a negated errno value.
+ */
+static int
+sg_sfp_blk_poll(struct sg_fd *sfp, int loop_count)
+{
+ int res = 0;
+ int n;
+ unsigned long idx;
+ struct sg_request *srp;
+ struct scsi_device *sdev = sfp->parentdp->device;
+ struct request_queue *q = sdev ? sdev->request_queue : NULL;
+ struct xarray *xafp = &sfp->srp_arr;
+
+ if (!q)
+ return -EINVAL;
+ xa_for_each(xafp, idx, srp) {
+ if (atomic_read(&srp->rq_st) != SG_RS_INFLIGHT)
+ continue;
+ if (!(srp->rq_flags & SGV4_FLAG_HIPRI))
+ continue;
+ n = sg_srp_q_blk_poll(srp, q, loop_count);
+ if (unlikely(n < 0))
+ return n;
+ res += n;
+ }
+ return res;
+}
+
+static inline int
+sg_srp_blk_poll(struct sg_request *srp, int loop_count)
+{
+ return sg_srp_q_blk_poll(srp,
srp->parentfp->parentdp->device->request_queue, loop_count);
+}
+
/*
* Implements the poll(2) system call for this driver. Returns
various EPOLL*
* flags OR-ed together.
@@ -2252,6 +2318,8 @@ sg_poll(struct file *filp, poll_table * wait)
__poll_t p_res = 0;
struct sg_fd *sfp = filp->private_data;
+ if (test_bit(SG_FFD_HIPRI_SEEN, sfp->ffd_bm))
+ sg_sfp_blk_poll(sfp, 0); /* LLD may have some ready to
push up */
num = atomic_read(&sfp->waiting);
if (num < 1) {
poll_wait(filp, &sfp->read_wait, wait);
@@ -2564,7 +2632,8 @@ sg_rq_end_io(struct request *rq, blk_status_t
status)
if (likely(rqq_state == SG_RS_AWAIT_RCV)) {
/* Wake any sg_read()/ioctl(SG_IORECEIVE) awaiting this req */
- wake_up_interruptible(&sfp->read_wait);
+ if (!(srp->rq_flags & SGV4_FLAG_HIPRI))
+ wake_up_interruptible(&sfp->read_wait);
kill_fasync(&sfp->async_qp, SIGPOLL, POLL_IN);
kref_put(&sfp->f_ref, sg_remove_sfp);
} else { /* clean up orphaned request that aren't being
kept */
@@ -3007,6 +3076,10 @@ sg_start_req(struct sg_request *srp, struct
sg_comm_wr_t *cwrp, int dxfer_dir)
/* current sg_request protected by SG_RS_BUSY state */
scsi_rp = scsi_req(rq);
srp->rq = rq;
+ if (rq_flags & SGV4_FLAG_HIPRI) {
+ if (!test_bit(SG_FFD_HIPRI_SEEN, sfp->ffd_bm))
+ set_bit(SG_FFD_HIPRI_SEEN, sfp->ffd_bm);
+ }
