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dm mpath: remove unnecessary NVMe branching in favor of scsi_dh checks 

This eliminates the "queue_mode" configuration's "nvme" mode.  There
wasn't anything NVMe-specific about that mode.  It was named "nvme"
because it was a short name for the mode.  But the entire point of the
mode was to optimize the multipath target for underlying devices that
are _not_ SCSI-based.  Devices that aren't SCSI have no need for the
various SCSI device handler (scsi_dh) specific code in DM multipath.

But rather than narrowly define this scsi_dh vs not branching in terms
of "nvme": invert the logic so that we're just checking whether a
multipath device is layered on SCSI devices with scsi_dh attached.

This allows any future storage technology to avoid scsi_dh specific code
in the multipath target too.

Fixes: 848b8aefd4 ("dm mpath: optimize NVMe bio-based support")
Suggested-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mike Snitzer 2018-03-05 14:10:11 -05:00
parent 99243b922c
commit 8d47e65948
1 changed files with 29 additions and 37 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

66
drivers/md/dm-mpath.c
View File

@ -22,6 +22,7 @@
#include <linux/time.h>
#include <linux/workqueue.h>
#include <linux/delay.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_dh.h>
#include <linux/atomic.h>
#include <linux/blk-mq.h>
@ -211,25 +212,13 @@ static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
else
m->queue_mode = DM_TYPE_REQUEST_BASED;
} else if (m->queue_mode == DM_TYPE_BIO_BASED ||
m->queue_mode == DM_TYPE_NVME_BIO_BASED) {
} else if (m->queue_mode == DM_TYPE_BIO_BASED) {
INIT_WORK(&m->process_queued_bios, process_queued_bios);
if (m->queue_mode == DM_TYPE_BIO_BASED) {
/*
* bio-based doesn't support any direct scsi_dh management;
* it just discovers if a scsi_dh is attached.
*/
set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
}
}
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);
/*
* bio-based doesn't support any direct scsi_dh management;
* it just discovers if a scsi_dh is attached.
*/
set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
}
dm_table_set_type(ti->table, m->queue_mode);
@ -337,14 +326,12 @@ 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);
set_bit(MPATHF_QUEUE_IO, &m->flags);
} else {
/* FIXME: not needed if no scsi_dh is attached */
clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
clear_bit(MPATHF_QUEUE_IO, &m->flags);
}
@ -385,8 +372,7 @@ static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
unsigned bypassed = 1;
if (!atomic_read(&m->nr_valid_paths)) {
if (m->queue_mode != DM_TYPE_NVME_BIO_BASED)
clear_bit(MPATHF_QUEUE_IO, &m->flags);
clear_bit(MPATHF_QUEUE_IO, &m->flags);
goto failed;
}
@ -599,7 +585,7 @@ static struct pgpath *__map_bio(struct multipath *m, struct bio *bio)
return pgpath;
}
static struct pgpath *__map_bio_nvme(struct multipath *m, struct bio *bio)
static struct pgpath *__map_bio_fast(struct multipath *m, struct bio *bio)
{
struct pgpath *pgpath;
unsigned long flags;
@ -634,8 +620,8 @@ static int __multipath_map_bio(struct multipath *m, struct bio *bio,
{
struct pgpath *pgpath;
if (m->queue_mode == DM_TYPE_NVME_BIO_BASED)
pgpath = __map_bio_nvme(m, bio);
if (!m->hw_handler_name)
pgpath = __map_bio_fast(m, bio);
else
pgpath = __map_bio(m, bio);
@ -675,8 +661,7 @@ static void process_queued_io_list(struct multipath *m)
{
if (m->queue_mode == DM_TYPE_MQ_REQUEST_BASED)
dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
else if (m->queue_mode == DM_TYPE_BIO_BASED ||
m->queue_mode == DM_TYPE_NVME_BIO_BASED)
else if (m->queue_mode == DM_TYPE_BIO_BASED)
queue_work(kmultipathd, &m->process_queued_bios);
}
@ -838,6 +823,16 @@ static int setup_scsi_dh(struct block_device *bdev, struct multipath *m, char **
*/
kfree(m->hw_handler_name);
m->hw_handler_name = attached_handler_name;
/*
* Init fields that are only used when a scsi_dh is attached
*/
if (!test_and_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);
}
}
}
@ -873,6 +868,7 @@ static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps
int r;
struct pgpath *p;
struct multipath *m = ti->private;
struct scsi_device *sdev;
/* we need at least a path arg */
if (as->argc < 1) {
@ -891,7 +887,9 @@ static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps
goto bad;
}
if (m->queue_mode != DM_TYPE_NVME_BIO_BASED) {
sdev = scsi_device_from_queue(bdev_get_queue(p->path.dev->bdev));
if (sdev) {
put_device(&sdev->sdev_gendev);
INIT_DELAYED_WORK(&p->activate_path, activate_path_work);
r = setup_scsi_dh(p->path.dev->bdev, m, &ti->error);
if (r) {
@ -1001,8 +999,7 @@ static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
if (!hw_argc)
return 0;
if (m->queue_mode == DM_TYPE_BIO_BASED ||
m->queue_mode == DM_TYPE_NVME_BIO_BASED) {
if (m->queue_mode == DM_TYPE_BIO_BASED) {
dm_consume_args(as, hw_argc);
DMERR("bio-based multipath doesn't allow hardware handler args");
return 0;
@ -1091,8 +1088,6 @@ static int parse_features(struct dm_arg_set *as, struct multipath *m)
if (!strcasecmp(queue_mode_name, "bio"))
m->queue_mode = DM_TYPE_BIO_BASED;
else if (!strcasecmp(queue_mode_name, "nvme"))
m->queue_mode = DM_TYPE_NVME_BIO_BASED;
else if (!strcasecmp(queue_mode_name, "rq"))
m->queue_mode = DM_TYPE_REQUEST_BASED;
else if (!strcasecmp(queue_mode_name, "mq"))
@ -1193,7 +1188,7 @@ static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
ti->num_discard_bios = 1;
ti->num_write_same_bios = 1;
ti->num_write_zeroes_bios = 1;
if (m->queue_mode == DM_TYPE_BIO_BASED || m->queue_mode == DM_TYPE_NVME_BIO_BASED)
if (m->queue_mode == DM_TYPE_BIO_BASED)
ti->per_io_data_size = multipath_per_bio_data_size();
else
ti->per_io_data_size = sizeof(struct dm_mpath_io);
@ -1730,9 +1725,6 @@ static void multipath_status(struct dm_target *ti, status_type_t type,
case DM_TYPE_BIO_BASED:
DMEMIT("queue_mode bio ");
break;
case DM_TYPE_NVME_BIO_BASED:
DMEMIT("queue_mode nvme ");
break;
case DM_TYPE_MQ_REQUEST_BASED:
DMEMIT("queue_mode mq ");
break;