[PATCH for-next 4/4] nvme-multipath: add multipathing for uring-passthrough commands

Kanchan Joshi
2022-07-11T11:08:44Z

From: Anuj Gupta <anuj20.g@samsung.com>

This heavily reuses nvme-mpath infrastructure for block-path.
Block-path operates on bio, and uses that as long-lived object across
requeue attempts. For passthrough interface io_uring_cmd happens to
be such object, so add a requeue list for that.

If path is not available, uring-cmds are added into that list and
resubmitted on discovery of new path. Existing requeue handler
(nvme_requeue_work) is extended to do this resubmission.

For failed commands, failover is done directly (i.e. without first
queuing into list) by resubmitting individual command from task-work
based callback.

Suggested-by: Sagi Grimberg <sagi@grimberg.me>
Co-developed-by: Kanchan Joshi <joshi.k@samsung.com>
Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
---
drivers/nvme/host/ioctl.c | 141 ++++++++++++++++++++++++++++++++--
drivers/nvme/host/multipath.c | 36 ++++++++-
drivers/nvme/host/nvme.h | 12 +++
include/linux/io_uring.h | 2 +
4 files changed, 182 insertions(+), 9 deletions(-)

diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
index fc02eddd4977..281c21d3c67d 100644
--- a/drivers/nvme/host/ioctl.c
+++ b/drivers/nvme/host/ioctl.c
@@ -340,12 +340,6 @@ struct nvme_uring_data {
__u32 timeout_ms;
};

-static inline struct nvme_uring_cmd_pdu *nvme_uring_cmd_pdu(
- struct io_uring_cmd *ioucmd)
-{
- return (struct nvme_uring_cmd_pdu *)&ioucmd->pdu;
-}
-
static void nvme_uring_task_cb(struct io_uring_cmd *ioucmd)
{
struct nvme_uring_cmd_pdu *pdu = nvme_uring_cmd_pdu(ioucmd);
@@ -448,6 +442,14 @@ static int nvme_uring_cmd_io(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
pdu->meta_buffer = nvme_to_user_ptr(d.metadata);
pdu->meta_len = d.metadata_len;

+ if (issue_flags & IO_URING_F_MPATH) {
+ req->cmd_flags |= REQ_NVME_MPATH;
+ /*
+ * we would need the buffer address (d.addr field) if we have
+ * to retry the command. Store it by repurposing ioucmd->cmd
+ */
+ ioucmd->cmd = (void *)d.addr;
+ }
blk_execute_rq_nowait(req, false);
return -EIOCBQUEUED;
}
@@ -665,12 +667,135 @@ int nvme_ns_head_chr_uring_cmd(struct io_uring_cmd *ioucmd,
int srcu_idx = srcu_read_lock(&head->srcu);
struct nvme_ns *ns = nvme_find_path(head);
int ret = -EINVAL;
+ struct device *dev = &head->cdev_device;
+
+ if (likely(ns)) {
+ ret = nvme_ns_uring_cmd(ns, ioucmd,
+ issue_flags | IO_URING_F_MPATH);
+ } else if (nvme_available_path(head)) {
+ struct nvme_uring_cmd_pdu *pdu = nvme_uring_cmd_pdu(ioucmd);
+ struct nvme_uring_cmd *payload = NULL;
+
+ dev_warn_ratelimited(dev, "no usable path - requeuing I/O\n");
+ /*
+ * We may requeue two kinds of uring commands:
+ * 1. command failed post submission. pdu->req will be non-null
+ * for this
+ * 2. command that could not be submitted because path was not
+ * available. For this pdu->req is set to NULL.
+ */
+ pdu->req = NULL;
+ /*
+ * passthrough command will not be available during retry as it
+ * is embedded in io_uring's SQE. Hence we allocate/copy here
+ */
+ payload = kmalloc(sizeof(struct nvme_uring_cmd), GFP_KERNEL);
+ if (!payload) {
+ ret = -ENOMEM;
+ goto out_unlock;
+ }
+ memcpy(payload, ioucmd->cmd, sizeof(struct nvme_uring_cmd));
+ ioucmd->cmd = payload;

- if (ns)
- ret = nvme_ns_uring_cmd(ns, ioucmd, issue_flags);
+ spin_lock_irq(&head->requeue_ioucmd_lock);
+ ioucmd_list_add(&head->requeue_ioucmd_list, ioucmd);
+ spin_unlock_irq(&head->requeue_ioucmd_lock);
+ ret = -EIOCBQUEUED;
+ } else {
+ dev_warn_ratelimited(dev, "no available path - failing I/O\n");
+ }
+out_unlock:
srcu_read_unlock(&head->srcu, srcu_idx);
return ret;
}
+
+int nvme_uring_cmd_io_retry(struct nvme_ns *ns, struct request *oreq,
+ struct io_uring_cmd *ioucmd, struct nvme_uring_cmd_pdu *pdu)
+{
+ struct nvme_ctrl *ctrl = ns->ctrl;
+ struct request_queue *q = ns ? ns->queue : ctrl->admin_q;
+ struct nvme_uring_data d;
+ struct nvme_command c;
+ struct request *req;
+ struct bio *obio = oreq->bio;
+ void *meta = NULL;
+
+ memcpy(&c, nvme_req(oreq)->cmd, sizeof(struct nvme_command));
+ d.metadata = (__u64)pdu->meta_buffer;
+ d.metadata_len = pdu->meta_len;
+ d.timeout_ms = oreq->timeout;
+ d.addr = (__u64)ioucmd->cmd;
+ if (obio) {
+ d.data_len = obio->bi_iter.bi_size;
+ blk_rq_unmap_user(obio);
+ } else {
+ d.data_len = 0;
+ }
+ blk_mq_free_request(oreq);
+ req = nvme_alloc_user_request(q, &c, nvme_to_user_ptr(d.addr),
+ d.data_len, nvme_to_user_ptr(d.metadata),
+ d.metadata_len, 0, &meta, d.timeout_ms ?
+ msecs_to_jiffies(d.timeout_ms) : 0,
+ ioucmd->cmd_op == NVME_URING_CMD_IO_VEC, 0, 0);
+ if (IS_ERR(req))
+ return PTR_ERR(req);
+
+ req->end_io = nvme_uring_cmd_end_io;
+ req->end_io_data = ioucmd;
+ pdu->bio = req->bio;
+ pdu->meta = meta;
+ req->cmd_flags |= REQ_NVME_MPATH;
+ blk_execute_rq_nowait(req, false);
+ return -EIOCBQUEUED;
+}
+
+void nvme_ioucmd_mpath_retry(struct io_uring_cmd *ioucmd)
+{
+ struct cdev *cdev = file_inode(ioucmd->file)->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);
+ unsigned int issue_flags = IO_URING_F_SQE128 | IO_URING_F_CQE32 |
+ IO_URING_F_MPATH;
+ struct device *dev = &head->cdev_device;
+
+ if (likely(ns)) {
+ struct nvme_uring_cmd_pdu *pdu = nvme_uring_cmd_pdu(ioucmd);
+ struct request *oreq = pdu->req;
+ int ret;
+
+ if (oreq == NULL) {
+ /*
+ * this was not submitted (to device) earlier. For this
+ * ioucmd->cmd points to persistent memory. Free that
+ * up post submission
+ */
+ const void *cmd = ioucmd->cmd;
+
+ ret = nvme_ns_uring_cmd(ns, ioucmd, issue_flags);
+ kfree(cmd);
+ } else {
+ /*
+ * this was submitted (to device) earlier. Use old
+ * request, bio (if it exists) and nvme-pdu to recreate
+ * the command for the discovered path
+ */
+ ret = nvme_uring_cmd_io_retry(ns, oreq, ioucmd, pdu);
+ }
+ if (ret != -EIOCBQUEUED)
+ io_uring_cmd_done(ioucmd, ret, 0);
+ } else if (nvme_available_path(head)) {
+ dev_warn_ratelimited(dev, "no usable path - requeuing I/O\n");
+ spin_lock_irq(&head->requeue_ioucmd_lock);
+ ioucmd_list_add(&head->requeue_ioucmd_list, ioucmd);
+ spin_unlock_irq(&head->requeue_ioucmd_lock);
+ } else {
+ dev_warn_ratelimited(dev, "no available path - failing I/O\n");
+ io_uring_cmd_done(ioucmd, -EINVAL, 0);
+ }
+ srcu_read_unlock(&head->srcu, srcu_idx);
+}
#endif /* CONFIG_NVME_MULTIPATH */

int nvme_dev_uring_cmd(struct io_uring_cmd *ioucmd, unsigned int issue_flags)
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index f26640ccb955..fe5655d98c36 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -6,6 +6,7 @@
#include <linux/backing-dev.h>
#include <linux/moduleparam.h>
#include <linux/vmalloc.h>
+#include <linux/io_uring.h>
#include <trace/events/block.h>
#include "nvme.h"

@@ -80,6 +81,17 @@ void nvme_mpath_start_freeze(struct nvme_subsystem *subsys)
blk_freeze_queue_start(h->disk->queue);
}

+static void nvme_ioucmd_failover_req(struct request *req, struct nvme_ns *ns)
+{
+ struct io_uring_cmd *ioucmd = req->end_io_data;
+ struct nvme_uring_cmd_pdu *pdu = nvme_uring_cmd_pdu(ioucmd);
+
+ /* store the request, to reconstruct the command during retry */
+ pdu->req = req;
+ /* retry in original submitter context */
+ io_uring_cmd_execute_in_task(ioucmd, nvme_ioucmd_mpath_retry);
+}
+
void nvme_failover_req(struct request *req)
{
struct nvme_ns *ns = req->q->queuedata;
@@ -99,6 +111,11 @@ void nvme_failover_req(struct request *req)
queue_work(nvme_wq, &ns->ctrl->ana_work);
}

+ if (blk_rq_is_passthrough(req)) {
+ nvme_ioucmd_failover_req(req, ns);
+ return;
+ }
+
spin_lock_irqsave(&ns->head->requeue_lock, flags);
for (bio = req->bio; bio; bio = bio->bi_next) {
bio_set_dev(bio, ns->head->disk->part0);
@@ -314,7 +331,7 @@ inline struct nvme_ns *nvme_find_path(struct nvme_ns_head *head)
return ns;
}

-static bool nvme_available_path(struct nvme_ns_head *head)
+bool nvme_available_path(struct nvme_ns_head *head)
{
struct nvme_ns *ns;

@@ -459,7 +476,9 @@ static void nvme_requeue_work(struct work_struct *work)
struct nvme_ns_head *head =
container_of(work, struct nvme_ns_head, requeue_work);
struct bio *bio, *next;
+ struct io_uring_cmd *ioucmd, *ioucmd_next;

+ /* process requeued bios*/
spin_lock_irq(&head->requeue_lock);
next = bio_list_get(&head->requeue_list);
spin_unlock_irq(&head->requeue_lock);
@@ -470,6 +489,21 @@ static void nvme_requeue_work(struct work_struct *work)

submit_bio_noacct(bio);
}
+
+ /* process requeued passthrough-commands */
+ spin_lock_irq(&head->requeue_ioucmd_lock);
+ ioucmd_next = ioucmd_list_get(&head->requeue_ioucmd_list);
+ spin_unlock_irq(&head->requeue_ioucmd_lock);
+
+ while ((ioucmd = ioucmd_next) != NULL) {
+ ioucmd_next = ioucmd->next;
+ ioucmd->next = NULL;
+ /*
+ * Retry in original submitter context as we would be
+ * processing the passthrough command again
+ */
+ io_uring_cmd_execute_in_task(ioucmd, nvme_ioucmd_mpath_retry);
+ }
}

int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl, struct nvme_ns_head *head)
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 9d3ff6feda06..125b48e74e72 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -16,6 +16,7 @@
#include <linux/rcupdate.h>
#include <linux/wait.h>
#include <linux/t10-pi.h>
+#include <linux/io_uring.h>

#include <trace/events/block.h>

@@ -189,6 +190,12 @@ enum {
NVME_REQ_USERCMD = (1 << 1),
};

+static inline struct nvme_uring_cmd_pdu *nvme_uring_cmd_pdu(
+ struct io_uring_cmd *ioucmd)
+{
+ return (struct nvme_uring_cmd_pdu *)&ioucmd->pdu;
+}
+
static inline struct nvme_request *nvme_req(struct request *req)
{
return blk_mq_rq_to_pdu(req);
@@ -442,6 +449,9 @@ struct nvme_ns_head {
struct work_struct requeue_work;
struct mutex lock;
unsigned long flags;
+ /* for uring-passthru multipath handling */
+ struct ioucmd_list requeue_ioucmd_list;
+ spinlock_t requeue_ioucmd_lock;
#define NVME_NSHEAD_DISK_LIVE 0
struct nvme_ns __rcu *current_path[];
#endif
@@ -830,6 +840,7 @@ int nvme_ns_chr_uring_cmd(struct io_uring_cmd *ioucmd,
unsigned int issue_flags);
int nvme_ns_head_chr_uring_cmd(struct io_uring_cmd *ioucmd,
unsigned int issue_flags);
+void nvme_ioucmd_mpath_retry(struct io_uring_cmd *ioucmd);
int nvme_getgeo(struct block_device *bdev, struct hd_geometry *geo);
int nvme_dev_uring_cmd(struct io_uring_cmd *ioucmd, unsigned int issue_flags);

@@ -844,6 +855,7 @@ static inline bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl)
return ctrl->ana_log_buf != NULL;
}

+bool nvme_available_path(struct nvme_ns_head *head);
void nvme_mpath_unfreeze(struct nvme_subsystem *subsys);
void nvme_mpath_wait_freeze(struct nvme_subsystem *subsys);
void nvme_mpath_start_freeze(struct nvme_subsystem *subsys);
diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
index d734599cbcd7..57f4dfc83316 100644
--- a/include/linux/io_uring.h
+++ b/include/linux/io_uring.h
@@ -15,6 +15,8 @@ enum io_uring_cmd_flags {
IO_URING_F_SQE128 = 4,
IO_URING_F_CQE32 = 8,
IO_URING_F_IOPOLL = 16,
+ /* to indicate that it is a MPATH req*/
+ IO_URING_F_MPATH = 32,
};

struct io_uring_cmd {
--
2.25.1