On 4/8/21 3:45 AM, Douglas Gilbert wrote:
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;
That _technically_ is a race condition;
the first atomic_read() call might return a different value than the
second one.
And this arguably is a mis-use of atomic _counters_, as here they are
just used to store fixed values, not counters per se.
Why not use 'READ/WRITE_ONCE' ?
+ 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, iflags;
+ 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_lock_irqsave(xafp, iflags);
+ xa_for_each(xafp, idx, srp) {
+ if ((srp->rq_flags & SGV4_FLAG_HIPRI) &&
+ atomic_read(&srp->rq_st) == SG_RS_INFLIGHT &&
+ test_bit(SG_FRQ_ISSUED, srp->frq_bm)) {
+ xa_unlock_irqrestore(xafp, iflags);
+ n = sg_srp_q_blk_poll(srp, q, loop_count);
+ if (n == -ENODATA)
+ n = 0;
+ if (unlikely(n < 0))
+ return n;
+ xa_lock_irqsave(xafp, iflags);
+ res += n;
+ }
+ }
+ xa_unlock_irqrestore(xafp, iflags);
+ return res;
+}
+
/*
* Implements the poll(2) system call for this driver. Returns various EPOLL*
* flags OR-ed together.
@@ -2239,6 +2323,8 @@ 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);
@@ -2523,6 +2609,7 @@ sg_rq_end_io(struct request *rqq, blk_status_t status)
}
}
xa_lock_irqsave(&sfp->srp_arr, iflags);
+ __set_bit(SG_FRQ_ISSUED, srp->frq_bm);
sg_rq_chg_state_force_ulck(srp, rqq_state);
WRITE_ONCE(srp->rqq, NULL);
if (test_bit(SG_FRQ_COUNT_ACTIVE, srp->frq_bm)) {
@@ -2548,7 +2635,8 @@ sg_rq_end_io(struct request *rqq, 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 */
@@ -2991,6 +3079,8 @@ 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(rqq);
WRITE_ONCE(srp->rqq, rqq);
+ if (rq_flags & SGV4_FLAG_HIPRI)
+ set_bit(SG_FFD_HIPRI_SEEN, sfp->ffd_bm);
if (cwrp->cmd_len > BLK_MAX_CDB)
scsi_rp->cmd = long_cmdp; /* transfer ownership */
@@ -3100,7 +3190,10 @@ sg_finish_scsi_blk_rq(struct sg_request *srp)
SG_LOG(4, sfp, "%s: srp=0x%pK%s\n", __func__, srp,
(srp->parentfp->rsv_srp == srp) ? " rsv" : "");
if (test_and_clear_bit(SG_FRQ_COUNT_ACTIVE, srp->frq_bm)) {
- atomic_dec(&sfp->submitted);
+ bool now_zero = atomic_dec_and_test(&sfp->submitted);
+
+ if (now_zero)
+ clear_bit(SG_FFD_HIPRI_SEEN, sfp->ffd_bm);
atomic_dec(&sfp->waiting);
}
Why the 'now_zero' variable?
I guess it can be dropped ...
@@ -3297,6 +3390,8 @@ sg_find_srp_by_id(struct sg_fd *sfp, int pack_id)
struct sg_request *srp = NULL;
struct xarray *xafp = &sfp->srp_arr;
+ if (test_bit(SG_FFD_HIPRI_SEEN, sfp->ffd_bm))
+ sg_sfp_blk_poll(sfp, 0); /* LLD may have some ready to push up */
if (num_waiting < 1) {
num_waiting = atomic_read_acquire(&sfp->waiting);
if (num_waiting < 1)
@@ -4101,8 +4196,9 @@ sg_proc_debug_sreq(struct sg_request *srp, int to, char *obp, int len)
else if (dur < U32_MAX) /* in-flight or busy (so ongoing) */
n += scnprintf(obp + n, len - n, " t_o/elap=%us/%ums",
to / 1000, dur);
- n += scnprintf(obp + n, len - n, " sgat=%d op=0x%02x\n",
- srp->sgat_h.num_sgat, srp->cmd_opcode);
+ cp = (srp->rq_flags & SGV4_FLAG_HIPRI) ? "hipri " : "";
+ n += scnprintf(obp + n, len - n, " sgat=%d %sop=0x%02x\n",
+ srp->sgat_h.num_sgat, cp, srp->cmd_opcode);
return n;
}
diff --git a/include/uapi/scsi/sg.h b/include/uapi/scsi/sg.h
index 6162a5d5995c..11b58b279241 100644
--- a/include/uapi/scsi/sg.h
+++ b/include/uapi/scsi/sg.h
@@ -110,6 +110,7 @@ typedef struct sg_io_hdr {
#define SGV4_FLAG_Q_AT_TAIL SG_FLAG_Q_AT_TAIL
#define SGV4_FLAG_Q_AT_HEAD SG_FLAG_Q_AT_HEAD
#define SGV4_FLAG_IMMED 0x400 /* for polling with SG_IOR, ignored in SG_IOS */
+#define SGV4_FLAG_HIPRI 0x800 /* request will use blk_poll to complete */
/* Output (potentially OR-ed together) in v3::info or v4::info field */
#define SG_INFO_OK_MASK 0x1
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer
