[PATCH 15/17] nvme: wire-up polling for uring-passthru

Kanchan Joshi
2022-03-08T15:43:20Z

From: Pankaj Raghav <p.raghav@samsung.com>

add .iopoll handler for char device (/dev/ngX), which in turn redirects
to bio_poll to implement polling.

Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
---
block/blk-mq.c | 3 +-
drivers/nvme/host/core.c | 1 +
drivers/nvme/host/ioctl.c | 79 ++++++++++++++++++++++++++++++++++-
drivers/nvme/host/multipath.c | 1 +
drivers/nvme/host/nvme.h | 4 ++
include/linux/blk-mq.h | 1 +
6 files changed, 86 insertions(+), 3 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 29f65eaf3e6b..6b37774b0d59 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1193,7 +1193,7 @@ void blk_execute_rq_nowait(struct request *rq, bool at_head, rq_end_io_fn *done)
}
EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);

-static bool blk_rq_is_poll(struct request *rq)
+bool blk_rq_is_poll(struct request *rq)
{
if (!rq->mq_hctx)
return false;
@@ -1203,6 +1203,7 @@ static bool blk_rq_is_poll(struct request *rq)
return false;
return true;
}
+EXPORT_SYMBOL_GPL(blk_rq_is_poll);

static void blk_rq_poll_completion(struct request *rq, struct completion *wait)
{
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 4a385001f124..64254771a28e 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3671,6 +3671,7 @@ static const struct file_operations nvme_ns_chr_fops = {
.unlocked_ioctl = nvme_ns_chr_ioctl,
.compat_ioctl = compat_ptr_ioctl,
.async_cmd = nvme_ns_chr_async_cmd,
+ .iopoll = nvme_iopoll,
};

static int nvme_add_ns_cdev(struct nvme_ns *ns)
diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
index a6712fb3eb98..701feaecabbe 100644
--- a/drivers/nvme/host/ioctl.c
+++ b/drivers/nvme/host/ioctl.c
@@ -37,6 +37,12 @@ static struct nvme_uring_cmd_pdu *nvme_uring_cmd_pdu(struct io_uring_cmd *ioucmd
return (struct nvme_uring_cmd_pdu *)&ioucmd->pdu;
}

+static inline bool is_polling_enabled(struct io_uring_cmd *ioucmd,
+ struct request *req)
+{
+ return (ioucmd->flags & IO_URING_F_UCMD_POLLED) && blk_rq_is_poll(req);
+}
+
static void nvme_pt_task_cb(struct io_uring_cmd *ioucmd)
{
struct nvme_uring_cmd_pdu *pdu = nvme_uring_cmd_pdu(ioucmd);
@@ -71,8 +77,17 @@ static void nvme_end_async_pt(struct request *req, blk_status_t err)

pdu->req = req;
req->bio = bio;
- /* this takes care of setting up task-work */
- io_uring_cmd_complete_in_task(ioucmd, nvme_pt_task_cb);
+
+ /*
+ * IO can be completed directly (i.e. without task work) if we are
+ * polling and in the task context already
+ */
+ if (is_polling_enabled(ioucmd, req)) {
+ nvme_pt_task_cb(ioucmd);
+ } else {
+ /* this takes care of setting up task-work */
+ io_uring_cmd_complete_in_task(ioucmd, nvme_pt_task_cb);
+ }
}

static void nvme_setup_uring_cmd_data(struct request *rq,
@@ -180,6 +195,10 @@ static int nvme_submit_user_cmd(struct request_queue *q,
if (ioucmd) { /* async dispatch */
if (cmd->common.opcode == nvme_cmd_write ||
cmd->common.opcode == nvme_cmd_read) {
+ if (bio && is_polling_enabled(ioucmd, req)) {
+ ioucmd->bio = bio;
+ bio->bi_opf |= REQ_POLLED;
+ }
nvme_setup_uring_cmd_data(req, ioucmd, meta, meta_buffer,
meta_len);
blk_execute_rq_nowait(req, 0, nvme_end_async_pt);
@@ -505,6 +524,32 @@ int nvme_ns_chr_async_cmd(struct io_uring_cmd *ioucmd)
return nvme_ns_async_ioctl(ns, ioucmd);
}

+int nvme_iopoll(struct kiocb *kiocb, struct io_comp_batch *iob,
+ unsigned int flags)
+{
+ struct bio *bio = NULL;
+ struct nvme_ns *ns = NULL;
+ struct request_queue *q = NULL;
+ int ret = 0;
+
+ rcu_read_lock();
+ bio = READ_ONCE(kiocb->private);
+ ns = container_of(file_inode(kiocb->ki_filp)->i_cdev, struct nvme_ns,
+ cdev);
+ q = ns->queue;
+ /*
+ * bio and driver_cb are a part of the same union inside io_uring_cmd
+ * struct. If driver is loaded without poll queues, completion will be
+ * IRQ based and driver_cb is populated. We do not want to treat that
+ * as bio and get into troubles. Avoid this by checking if queue is
+ * polled and bail out if not.
+ */
+ if ((test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) && bio && bio->bi_bdev)
+ ret = bio_poll(bio, iob, flags);
+ rcu_read_unlock();
+ return ret;
+}
+
#ifdef CONFIG_NVME_MULTIPATH
static int nvme_ns_head_ctrl_ioctl(struct nvme_ns *ns, unsigned int cmd,
void __user *argp, struct nvme_ns_head *head, int srcu_idx)
@@ -585,6 +630,36 @@ long nvme_ns_head_chr_ioctl(struct file *file, unsigned int cmd,
srcu_read_unlock(&head->srcu, srcu_idx);
return ret;
}
+
+int nvme_ns_head_iopoll(struct kiocb *kiocb, struct io_comp_batch *iob,
+ unsigned int flags)
+{
+ struct bio *bio = NULL;
+ struct request_queue *q = NULL;
+ struct cdev *cdev = file_inode(kiocb->ki_filp)->i_cdev;
+ struct nvme_ns_head *head = container_of(cdev, struct nvme_ns_head, cdev);
+ int srcu_idx = srcu_read_lock(&head->srcu);
+ struct nvme_ns *ns = nvme_find_path(head);
+ int ret = -EWOULDBLOCK;
+
+ if (ns) {
+ bio = READ_ONCE(kiocb->private);
+ q = ns->queue;
+ /*
+ * bio and driver_cb are part of same union inside io_uring_cmd
+ * struct. If driver is loaded without poll queues, completion
+ * will be IRQ based and driver_cb is populated. We do not want
+ * to treat that as bio and get into troubles. Avoid this by
+ * checking if queue is polled, and bail out if not.
+ */
+ if ((test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) && bio &&
+ bio->bi_bdev)
+ ret = bio_poll(bio, iob, flags);
+ }
+
+ srcu_read_unlock(&head->srcu, srcu_idx);
+ return ret;
+}
#endif /* CONFIG_NVME_MULTIPATH */

static int nvme_dev_user_cmd(struct nvme_ctrl *ctrl, void __user *argp)
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 1d798d09456f..27995358c847 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -460,6 +460,7 @@ static const struct file_operations nvme_ns_head_chr_fops = {
.unlocked_ioctl = nvme_ns_head_chr_ioctl,
.compat_ioctl = compat_ptr_ioctl,
.async_cmd = nvme_ns_head_chr_async_cmd,
+ .iopoll = nvme_ns_head_iopoll,
};

static int nvme_add_ns_head_cdev(struct nvme_ns_head *head)
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 9a3e5093dedc..0be437c25077 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -755,7 +755,11 @@ long nvme_ns_head_chr_ioctl(struct file *file, unsigned int cmd,
long nvme_dev_ioctl(struct file *file, unsigned int cmd,
unsigned long arg);
int nvme_ns_chr_async_cmd(struct io_uring_cmd *ioucmd);
+int nvme_iopoll(struct kiocb *kiocb, struct io_comp_batch *iob,
+ unsigned int flags);
int nvme_ns_head_chr_async_cmd(struct io_uring_cmd *ioucmd);
+int nvme_ns_head_iopoll(struct kiocb *kiocb, struct io_comp_batch *iob,
+ unsigned int flags);
int nvme_getgeo(struct block_device *bdev, struct hd_geometry *geo);

extern const struct attribute_group *nvme_ns_id_attr_groups[];
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 5f21f71b2529..9f00b2a5a991 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -977,6 +977,7 @@ int blk_rq_map_kern(struct request_queue *, struct request *, void *,
int blk_rq_append_bio(struct request *rq, struct bio *bio);
void blk_execute_rq_nowait(struct request *rq, bool at_head,
rq_end_io_fn *end_io);
+bool blk_rq_is_poll(struct request *rq);
blk_status_t blk_execute_rq(struct request *rq, bool at_head);

struct req_iterator {
--
2.25.1