From 91e968aa6015d7366281b532dad2e48855b91fe3 Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Thu, 17 Mar 2016 17:10:15 -0400 Subject: [PATCH] dm mpath: use atomic_t for counting members of 'struct multipath' The use of atomic_t for nr_valid_paths, pg_init_in_progress and pg_init_count will allow relaxing the use of the m->lock spinlock. Suggested-by: Hannes Reinecke Reviewed-by: Hannes Reinecke Tested-by: Hannes Reinecke Signed-off-by: Mike Snitzer --- drivers/md/dm-mpath.c | 61 +++++++++++++++++++++++-------------------- 1 file changed, 33 insertions(+), 28 deletions(-) diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c index 598d4a1123e0..780e5d0a066f 100644 --- a/drivers/md/dm-mpath.c +++ b/drivers/md/dm-mpath.c @@ -76,9 +76,6 @@ struct multipath { wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */ - unsigned pg_init_in_progress; /* Only one pg_init allowed at once */ - - unsigned nr_valid_paths; /* Total number of usable paths */ struct pgpath *current_pgpath; struct priority_group *current_pg; struct priority_group *next_pg; /* Switch to this PG if set */ @@ -86,9 +83,12 @@ struct multipath { unsigned long flags; /* Multipath state flags */ unsigned pg_init_retries; /* Number of times to retry pg_init */ - unsigned pg_init_count; /* Number of times pg_init called */ 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 */ + struct work_struct trigger_event; /* @@ -195,6 +195,9 @@ static struct multipath *alloc_multipath(struct dm_target *ti, bool use_blk_mq) 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); @@ -279,10 +282,10 @@ static int __pg_init_all_paths(struct multipath *m) struct pgpath *pgpath; unsigned long pg_init_delay = 0; - if (m->pg_init_in_progress || test_bit(MPATHF_PG_INIT_DISABLED, &m->flags)) + if (atomic_read(&m->pg_init_in_progress) || test_bit(MPATHF_PG_INIT_DISABLED, &m->flags)) return 0; - m->pg_init_count++; + atomic_inc(&m->pg_init_count); clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags); /* Check here to reset pg_init_required */ @@ -298,9 +301,9 @@ static int __pg_init_all_paths(struct multipath *m) continue; if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path, pg_init_delay)) - m->pg_init_in_progress++; + atomic_inc(&m->pg_init_in_progress); } - return m->pg_init_in_progress; + return atomic_read(&m->pg_init_in_progress); } static void __switch_pg(struct multipath *m, struct pgpath *pgpath) @@ -316,7 +319,7 @@ static void __switch_pg(struct multipath *m, struct pgpath *pgpath) clear_bit(MPATHF_QUEUE_IO, &m->flags); } - m->pg_init_count = 0; + atomic_set(&m->pg_init_count, 0); } static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg, @@ -341,7 +344,7 @@ static void __choose_pgpath(struct multipath *m, size_t nr_bytes) struct priority_group *pg; bool bypassed = true; - if (!m->nr_valid_paths) { + if (!atomic_read(&m->nr_valid_paths)) { clear_bit(MPATHF_QUEUE_IO, &m->flags); goto failed; } @@ -902,6 +905,7 @@ static int multipath_ctr(struct dm_target *ti, unsigned int argc, /* parse the priority groups */ while (as.argc) { struct priority_group *pg; + unsigned nr_valid_paths = atomic_read(&m->nr_valid_paths); pg = parse_priority_group(&as, m); if (IS_ERR(pg)) { @@ -909,7 +913,9 @@ static int multipath_ctr(struct dm_target *ti, unsigned int argc, goto bad; } - m->nr_valid_paths += pg->nr_pgpaths; + nr_valid_paths += pg->nr_pgpaths; + atomic_set(&m->nr_valid_paths, nr_valid_paths); + list_add_tail(&pg->list, &m->priority_groups); pg_count++; pg->pg_num = pg_count; @@ -939,19 +945,14 @@ static int multipath_ctr(struct dm_target *ti, unsigned int argc, static void multipath_wait_for_pg_init_completion(struct multipath *m) { DECLARE_WAITQUEUE(wait, current); - unsigned long flags; add_wait_queue(&m->pg_init_wait, &wait); while (1) { set_current_state(TASK_UNINTERRUPTIBLE); - spin_lock_irqsave(&m->lock, flags); - if (!m->pg_init_in_progress) { - spin_unlock_irqrestore(&m->lock, flags); + if (!atomic_read(&m->pg_init_in_progress)) break; - } - spin_unlock_irqrestore(&m->lock, flags); io_schedule(); } @@ -1001,13 +1002,13 @@ static int fail_path(struct pgpath *pgpath) pgpath->is_active = false; pgpath->fail_count++; - m->nr_valid_paths--; + atomic_dec(&m->nr_valid_paths); if (pgpath == m->current_pgpath) m->current_pgpath = NULL; dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti, - pgpath->path.dev->name, m->nr_valid_paths); + pgpath->path.dev->name, atomic_read(&m->nr_valid_paths)); schedule_work(&m->trigger_event); @@ -1025,6 +1026,7 @@ static int reinstate_path(struct pgpath *pgpath) int r = 0, run_queue = 0; unsigned long flags; struct multipath *m = pgpath->pg->m; + unsigned nr_valid_paths; spin_lock_irqsave(&m->lock, flags); @@ -1039,16 +1041,17 @@ static int reinstate_path(struct pgpath *pgpath) pgpath->is_active = true; - if (!m->nr_valid_paths++) { + nr_valid_paths = atomic_inc_return(&m->nr_valid_paths); + if (nr_valid_paths == 1) { m->current_pgpath = NULL; run_queue = 1; } 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++; + atomic_inc(&m->pg_init_in_progress); } dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti, - pgpath->path.dev->name, m->nr_valid_paths); + pgpath->path.dev->name, nr_valid_paths); schedule_work(&m->trigger_event); @@ -1166,7 +1169,8 @@ static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath) spin_lock_irqsave(&m->lock, flags); - if (m->pg_init_count <= m->pg_init_retries && !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags)) + if (atomic_read(&m->pg_init_count) <= m->pg_init_retries && + !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags)) set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags); else limit_reached = true; @@ -1236,7 +1240,7 @@ static void pg_init_done(void *data, int errors) } else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) pg->bypassed = false; - if (--m->pg_init_in_progress) + if (atomic_dec_return(&m->pg_init_in_progress) > 0) /* Activations of other paths are still on going */ goto out; @@ -1317,7 +1321,7 @@ static int do_end_io(struct multipath *m, struct request *clone, fail_path(mpio->pgpath); spin_lock_irqsave(&m->lock, flags); - if (!m->nr_valid_paths) { + if (!atomic_read(&m->nr_valid_paths)) { if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) { if (!__must_push_back(m)) r = -EIO; @@ -1421,7 +1425,8 @@ static void multipath_status(struct dm_target *ti, status_type_t type, /* Features */ if (type == STATUSTYPE_INFO) - DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags), m->pg_init_count); + DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags), + atomic_read(&m->pg_init_count)); else { DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) + (m->pg_init_retries > 0) * 2 + @@ -1675,8 +1680,8 @@ static int multipath_busy(struct dm_target *ti) spin_lock_irqsave(&m->lock, flags); /* pg_init in progress or no paths available */ - if (m->pg_init_in_progress || - (!m->nr_valid_paths && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))) { + if (atomic_read(&m->pg_init_in_progress) || + (!atomic_read(&m->nr_valid_paths) && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))) { busy = true; goto out; }