dm mpath: optimize NVMe bio-based support

All code that deals with pg_init is not used with bio-based NVMe mode.
This includes skipping initialization of pg_init related variables.

Also, pg_init related members on 'struct multipath' have been grouped
together.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index d3813b1..fa5ee78 100644 (file)
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -64,36 +64,30 @@ struct priority_group {
 
 /* Multipath context */
 struct multipath {
-       struct list_head list;
-       struct dm_target *ti;
-
-       const char *hw_handler_name;
-       char *hw_handler_params;
+       unsigned long flags;            /* Multipath state flags */
 
        spinlock_t lock;
-
-       unsigned nr_priority_groups;
-       struct list_head priority_groups;
-
-       wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
+       enum dm_queue_mode queue_mode;
 
        struct pgpath *current_pgpath;
        struct priority_group *current_pg;
        struct priority_group *next_pg; /* Switch to this PG if set */
 
-       unsigned long flags;            /* Multipath state flags */
+       atomic_t nr_valid_paths;        /* Total number of usable paths */
+       unsigned nr_priority_groups;
+       struct list_head priority_groups;
 
+       const char *hw_handler_name;
+       char *hw_handler_params;
+       wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
        unsigned pg_init_retries;       /* Number of times to retry pg_init */
        unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
-
-       atomic_t nr_valid_paths;        /* Total number of usable paths */
        atomic_t pg_init_in_progress;   /* Only one pg_init allowed at once */
        atomic_t pg_init_count;         /* Number of times pg_init called */
 
-       enum dm_queue_mode queue_mode;
-
        struct mutex work_mutex;
        struct work_struct trigger_event;
+       struct dm_target *ti;
 
        struct work_struct process_queued_bios;
        struct bio_list queued_bios;
@@ -135,10 +129,10 @@ static struct pgpath *alloc_pgpath(void)
 {
        struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 
-       if (pgpath) {
-               pgpath->is_active = true;
-               INIT_DELAYED_WORK(&pgpath->activate_path, activate_path_work);
-       }
+       if (!pgpath)
+               return NULL;
+
+       pgpath->is_active = true;
 
        return pgpath;
 }
@@ -193,13 +187,8 @@ static struct multipath *alloc_multipath(struct dm_target *ti)
        if (m) {
                INIT_LIST_HEAD(&m->priority_groups);
                spin_lock_init(&m->lock);
-               set_bit(MPATHF_QUEUE_IO, &m->flags);
                atomic_set(&m->nr_valid_paths, 0);
-               atomic_set(&m->pg_init_in_progress, 0);
-               atomic_set(&m->pg_init_count, 0);
-               m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
                INIT_WORK(&m->trigger_event, trigger_event);
-               init_waitqueue_head(&m->pg_init_wait);
                mutex_init(&m->work_mutex);
 
                m->queue_mode = DM_TYPE_NONE;
@@ -235,6 +224,14 @@ static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
                }
        }
 
+       if (m->queue_mode != DM_TYPE_NVME_BIO_BASED) {
+               set_bit(MPATHF_QUEUE_IO, &m->flags);
+               atomic_set(&m->pg_init_in_progress, 0);
+               atomic_set(&m->pg_init_count, 0);
+               m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
+               init_waitqueue_head(&m->pg_init_wait);
+       }
+
        dm_table_set_type(ti->table, m->queue_mode);
 
        return 0;
@@ -339,6 +336,9 @@ static void __switch_pg(struct multipath *m, struct priority_group *pg)
 {
        m->current_pg = pg;
 
+       if (m->queue_mode == DM_TYPE_NVME_BIO_BASED)
+               return;
+
        /* Must we initialise the PG first, and queue I/O till it's ready? */
        if (m->hw_handler_name) {
                set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
@@ -384,7 +384,8 @@ static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
        unsigned bypassed = 1;
 
        if (!atomic_read(&m->nr_valid_paths)) {
-               clear_bit(MPATHF_QUEUE_IO, &m->flags);
+               if (m->queue_mode != DM_TYPE_NVME_BIO_BASED)
+                       clear_bit(MPATHF_QUEUE_IO, &m->flags);
                goto failed;
        }
 
@@ -528,8 +529,7 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
        clone = blk_get_request(q, rq->cmd_flags | REQ_NOMERGE, GFP_ATOMIC);
        if (IS_ERR(clone)) {
                /* EBUSY, ENODEV or EWOULDBLOCK: requeue */
-               bool queue_dying = blk_queue_dying(q);
-               if (queue_dying) {
+               if (blk_queue_dying(q)) {
                        atomic_inc(&m->pg_init_in_progress);
                        activate_or_offline_path(pgpath);
                }
@@ -563,21 +563,28 @@ static int __multipath_map_bio(struct multipath *m, struct bio *bio, struct dm_m
 
        /* Do we need to select a new pgpath? */
        pgpath = READ_ONCE(m->current_pgpath);
+       /* MPATHF_QUEUE_IO will never be set for NVMe */
        queue_io = test_bit(MPATHF_QUEUE_IO, &m->flags);
        if (!pgpath || !queue_io)
                pgpath = choose_pgpath(m, mpio->nr_bytes);
 
-       if ((pgpath && queue_io) ||
-           (!pgpath && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))) {
+       if ((!pgpath && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) ||
+           (pgpath && queue_io)) {
                /* Queue for the daemon to resubmit */
                spin_lock_irqsave(&m->lock, flags);
                bio_list_add(&m->queued_bios, bio);
                spin_unlock_irqrestore(&m->lock, flags);
-               /* PG_INIT_REQUIRED cannot be set without QUEUE_IO */
-               if (queue_io || test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
-                       pg_init_all_paths(m);
-               else if (!queue_io)
+
+               if (m->queue_mode == DM_TYPE_NVME_BIO_BASED) {
                        queue_work(kmultipathd, &m->process_queued_bios);
+               } else {
+                       /* PG_INIT_REQUIRED cannot be set without QUEUE_IO */
+                       if (queue_io || test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
+                               pg_init_all_paths(m);
+                       else if (!queue_io)
+                               queue_work(kmultipathd, &m->process_queued_bios);
+               }
+
                return DM_MAPIO_SUBMITTED;
        }
 
@@ -750,34 +757,11 @@ static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
        return 0;
 }
 
-static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
-                              struct dm_target *ti)
+static int setup_scsi_dh(struct block_device *bdev, struct multipath *m, char **error)
 {
-       int r;
-       struct pgpath *p;
-       struct multipath *m = ti->private;
-       struct request_queue *q = NULL;
+       struct request_queue *q = bdev_get_queue(bdev);
        const char *attached_handler_name;
-
-       /* we need at least a path arg */
-       if (as->argc < 1) {
-               ti->error = "no device given";
-               return ERR_PTR(-EINVAL);
-       }
-
-       p = alloc_pgpath();
-       if (!p)
-               return ERR_PTR(-ENOMEM);
-
-       r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
-                         &p->path.dev);
-       if (r) {
-               ti->error = "error getting device";
-               goto bad;
-       }
-
-       if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) || m->hw_handler_name)
-               q = bdev_get_queue(p->path.dev->bdev);
+       int r;
 
        if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags)) {
 retain:
@@ -809,26 +793,59 @@ retain:
                        char b[BDEVNAME_SIZE];
 
                        printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
-                               bdevname(p->path.dev->bdev, b));
+                              bdevname(bdev, b));
                        goto retain;
                }
                if (r < 0) {
-                       ti->error = "error attaching hardware handler";
-                       dm_put_device(ti, p->path.dev);
-                       goto bad;
+                       *error = "error attaching hardware handler";
+                       return r;
                }
 
                if (m->hw_handler_params) {
                        r = scsi_dh_set_params(q, m->hw_handler_params);
                        if (r < 0) {
-                               ti->error = "unable to set hardware "
-                                                       "handler parameters";
-                               dm_put_device(ti, p->path.dev);
-                               goto bad;
+                               *error = "unable to set hardware handler parameters";
+                               return r;
                        }
                }
        }
 
+       return 0;
+}
+
+static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
+                                struct dm_target *ti)
+{
+       int r;
+       struct pgpath *p;
+       struct multipath *m = ti->private;
+
+       /* we need at least a path arg */
+       if (as->argc < 1) {
+               ti->error = "no device given";
+               return ERR_PTR(-EINVAL);
+       }
+
+       p = alloc_pgpath();
+       if (!p)
+               return ERR_PTR(-ENOMEM);
+
+       r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
+                         &p->path.dev);
+       if (r) {
+               ti->error = "error getting device";
+               goto bad;
+       }
+
+       if (m->queue_mode != DM_TYPE_NVME_BIO_BASED) {
+               INIT_DELAYED_WORK(&p->activate_path, activate_path_work);
+               r = setup_scsi_dh(p->path.dev->bdev, m, &ti->error);
+               if (r) {
+                       dm_put_device(ti, p->path.dev);
+                       goto bad;
+               }
+       }
+
        r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
        if (r) {
                dm_put_device(ti, p->path.dev);
@@ -836,7 +853,6 @@ retain:
        }
 
        return p;
-
  bad:
        free_pgpath(p);
        return ERR_PTR(r);
@@ -1152,16 +1168,19 @@ static void multipath_wait_for_pg_init_completion(struct multipath *m)
 
 static void flush_multipath_work(struct multipath *m)
 {
-       set_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
-       smp_mb__after_atomic();
+       if (m->hw_handler_name) {
+               set_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
+               smp_mb__after_atomic();
+
+               flush_workqueue(kmpath_handlerd);
+               multipath_wait_for_pg_init_completion(m);
+
+               clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
+               smp_mb__after_atomic();
+       }
 
-       flush_workqueue(kmpath_handlerd);
-       multipath_wait_for_pg_init_completion(m);
        flush_workqueue(kmultipathd);
        flush_work(&m->trigger_event);
-
-       clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
-       smp_mb__after_atomic();
 }
 
 static void multipath_dtr(struct dm_target *ti)
@@ -1537,7 +1556,7 @@ static int multipath_end_io(struct dm_target *ti, struct request *clone,
 }
 
 static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
-               blk_status_t *error)
+                               blk_status_t *error)
 {
        struct multipath *m = ti->private;
        struct dm_mpath_io *mpio = get_mpio_from_bio(clone);