From: Hannes Reinecke <hare@xxxxxxx>
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.
We only need to take care to add a small delay when calling
__pg_init_all_paths() to move processing off to a workqueue; otherwise
pg_init_done() might end up calling scsi_dh_activate() directly, which
might use non-atomic memory allocations or issue I/O.
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
Cc: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
drivers/md/dm-mpath.c | 63 ++++++++++++++++++---------------------------------
1 file changed, 22 insertions(+), 41 deletions(-)
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 89c0997..b99cff0 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -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);
@@ -254,10 +250,10 @@ static void clear_mapinfo(struct multipath *m, union map_info *info)
* Path selection
*-----------------------------------------------*/
-static void __pg_init_all_paths(struct multipath *m)
+static void __pg_init_all_paths(struct multipath *m, unsigned long min_delay)
{
struct pgpath *pgpath;
- unsigned long pg_init_delay = 0;
+ unsigned long pg_init_delay = min_delay;
if (m->pg_init_in_progress || m->pg_init_disabled)
return;
@@ -406,7 +402,7 @@ static int map_io(struct multipath *m, struct request *clone,
&pgpath->path,
nr_bytes);
} else {
- __pg_init_all_paths(m);
+ __pg_init_all_paths(m, 0);
r = DM_MAPIO_REQUEUE;
}
} else {
@@ -438,40 +434,13 @@ 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.
@@ -1018,7 +987,7 @@ 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++;
@@ -1216,9 +1185,12 @@ static void pg_init_done(void *data, int errors)
if (!m->pg_init_required)
m->queue_io = 0;
-
- m->pg_init_delay_retry = delay_retry;
- queue_work(kmultipathd, &m->process_queued_ios);
+ else if (m->current_pg) {
+ m->pg_init_delay_retry = delay_retry;
+ /* Use a small delay to force the use of workqueue context */
+ __pg_init_all_paths(m, 50/HZ);
+ goto out;
+ }
/*
* Wake up any thread waiting to suspend.
@@ -1591,8 +1563,17 @@ static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
if (!r && ti->len != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT)
r = scsi_verify_blk_ioctl(NULL, cmd);
- 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->current_pg && m->pg_init_required)
+ __pg_init_all_paths(m, 0);
+ spin_unlock_irqrestore(&m->lock, flags);
+ dm_table_run_md_queue_async(m->ti->table);
+ }
return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
}
--
1.8.1.4
--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel
