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dm mpath: remove process_queued_ios() 

process_queued_ios() has served 3 functions:
  1) select pg and pgpath if none is selected
  2) start pg_init if requested
  3) dispatch queued IOs when pg is ready

Basically, a call to queue_work(process_queued_ios) can be replaced by
dm_table_run_md_queue_async(), which runs request queue and ends up
calling map_io(), which does 1), 2) and 3).

Exception is when !pg_ready() (which means either pg_init is running or
requested), then multipath_busy() prevents map_io() being called from
request_fn.

If pg_init is running, it should be ok as long as pg_init_done() does
the right thing when pg_init is completed, I.e.: restart pg_init if
!pg_ready() or call dm_table_run_md_queue_async() to kick map_io().

If pg_init is requested, we have to make sure the request is detected
and pg_init will be started.  pg_init is requested in 3 places:
  a) __choose_pgpath() in map_io()
  b) __choose_pgpath() in multipath_ioctl()
  c) pg_init retry in pg_init_done()
a) is ok because map_io() calls __pg_init_all_paths(), which does 2).
b) needs a call to __pg_init_all_paths(), which does 2).
c) needs a call to __pg_init_all_paths(), which does 2).

So this patch removes process_queued_ios() and ensures that
__pg_init_all_paths() is called at the appropriate locations.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
This commit is contained in:
Hannes Reinecke 2014-02-28 15:33:45 +01:00 committed by Mike Snitzer
parent e809917735
commit 3e9f1be1b4
1 changed files with 27 additions and 42 deletions
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69
drivers/md/dm-mpath.c
View File

@ -93,8 +93,6 @@ struct multipath {
unsigned pg_init_count; /* Number of times pg_init called */
unsigned pg_init_delay_msecs; /* Number of msecs before pg_init retry */
struct work_struct process_queued_ios;
struct work_struct trigger_event;
/*
@ -119,7 +117,6 @@ typedef int (*action_fn) (struct pgpath *pgpath);
static struct kmem_cache *_mpio_cache;
static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
static void process_queued_ios(struct work_struct *work);
static void trigger_event(struct work_struct *work);
static void activate_path(struct work_struct *work);
static int __pgpath_busy(struct pgpath *pgpath);
@ -197,7 +194,6 @@ static struct multipath *alloc_multipath(struct dm_target *ti)
spin_lock_init(&m->lock);
m->queue_io = 1;
m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
INIT_WORK(&m->process_queued_ios, process_queued_ios);
INIT_WORK(&m->trigger_event, trigger_event);
init_waitqueue_head(&m->pg_init_wait);
mutex_init(&m->work_mutex);
@ -254,16 +250,21 @@ static void clear_mapinfo(struct multipath *m, union map_info *info)
* Path selection
*-----------------------------------------------*/
static void __pg_init_all_paths(struct multipath *m)
static int __pg_init_all_paths(struct multipath *m)
{
struct pgpath *pgpath;
unsigned long pg_init_delay = 0;
if (m->pg_init_in_progress || m->pg_init_disabled)
return;
return 0;
m->pg_init_count++;
m->pg_init_required = 0;
/* Check here to reset pg_init_required */
if (!m->current_pg)
return 0;
if (m->pg_init_delay_retry)
pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
@ -275,6 +276,7 @@ static void __pg_init_all_paths(struct multipath *m)
pg_init_delay))
m->pg_init_in_progress++;
}
return m->pg_init_in_progress;
}
static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
@ -436,40 +438,13 @@ static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
m->saved_queue_if_no_path = queue_if_no_path;
m->queue_if_no_path = queue_if_no_path;
if (!m->queue_if_no_path)
queue_work(kmultipathd, &m->process_queued_ios);
dm_table_run_md_queue_async(m->ti->table);
spin_unlock_irqrestore(&m->lock, flags);
return 0;
}
static void process_queued_ios(struct work_struct *work)
{
struct multipath *m =
container_of(work, struct multipath, process_queued_ios);
struct pgpath *pgpath = NULL;
unsigned must_queue = 1;
unsigned long flags;
spin_lock_irqsave(&m->lock, flags);
if (!m->current_pgpath)
__choose_pgpath(m, 0);
pgpath = m->current_pgpath;
if ((pgpath && !m->queue_io) ||
(!pgpath && !m->queue_if_no_path))
must_queue = 0;
if (pgpath && m->pg_init_required)
__pg_init_all_paths(m);
spin_unlock_irqrestore(&m->lock, flags);
if (!must_queue)
dm_table_run_md_queue_async(m->ti->table);
}
/*
* An event is triggered whenever a path is taken out of use.
* Includes path failure and PG bypass.
@ -1016,7 +991,7 @@ static int reinstate_path(struct pgpath *pgpath)
if (!m->nr_valid_paths++) {
m->current_pgpath = NULL;
queue_work(kmultipathd, &m->process_queued_ios);
dm_table_run_md_queue_async(m->ti->table);
} else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
m->pg_init_in_progress++;
@ -1212,11 +1187,12 @@ static void pg_init_done(void *data, int errors)
/* Activations of other paths are still on going */
goto out;
if (!m->pg_init_required)
m->queue_io = 0;
m->pg_init_delay_retry = delay_retry;
queue_work(kmultipathd, &m->process_queued_ios);
if (m->pg_init_required) {
m->pg_init_delay_retry = delay_retry;
if (__pg_init_all_paths(m))
goto out;
}
m->queue_io = 0;
/*
* Wake up any thread waiting to suspend.
@ -1592,8 +1568,17 @@ static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
r = err;
}
if (r == -ENOTCONN && !fatal_signal_pending(current))
queue_work(kmultipathd, &m->process_queued_ios);
if (r == -ENOTCONN && !fatal_signal_pending(current)) {
spin_lock_irqsave(&m->lock, flags);
if (!m->current_pg) {
/* Path status changed, redo selection */
__choose_pgpath(m, 0);
}
if (m->pg_init_required)
__pg_init_all_paths(m);
spin_unlock_irqrestore(&m->lock, flags);
dm_table_run_md_queue_async(m->ti->table);
}
return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
}