On Sun, 1 Dec 2019, Eric Wheeler wrote:
> On Tue, 15 Oct 2019, Mikulas Patocka wrote:
>
> > If we are in a place where it is known that interrupts are enabled,
> > functions spin_lock_irq/spin_unlock_irq should be used instead of
> > spin_lock_irqsave/spin_unlock_irqrestore.
> >
> > spin_lock_irq and spin_unlock_irq are faster because the don't need to
> > push and pop the flags register.
>
> Hi Mikulas,
>
> This cherry-picks clean into 4.19.y. Is there any reason this would be
> unsafe in that kernel? This provides a minor performance gain and we
> might pick it up internally unless you forsee a problem.
>
> Thanks!
>
> --
> Eric Wheeler
I think there is nothing that could break if you backport it.
Mikulas
> > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> >
> > ---
> > drivers/md/dm-thin.c | 113 ++++++++++++++++++++-------------------------------
> > 1 file changed, 46 insertions(+), 67 deletions(-)
> >
> > Index: linux-2.6/drivers/md/dm-thin.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/md/dm-thin.c 2019-10-11 18:57:08.000000000 +0200
> > +++ linux-2.6/drivers/md/dm-thin.c 2019-10-11 21:33:40.000000000 +0200
> > @@ -609,13 +609,12 @@ static void error_thin_bio_list(struct t
> > blk_status_t error)
> > {
> > struct bio_list bios;
> > - unsigned long flags;
> >
> > bio_list_init(&bios);
> >
> > - spin_lock_irqsave(&tc->lock, flags);
> > + spin_lock_irq(&tc->lock);
> > __merge_bio_list(&bios, master);
> > - spin_unlock_irqrestore(&tc->lock, flags);
> > + spin_unlock_irq(&tc->lock);
> >
> > error_bio_list(&bios, error);
> > }
> > @@ -623,15 +622,14 @@ static void error_thin_bio_list(struct t
> > static void requeue_deferred_cells(struct thin_c *tc)
> > {
> > struct pool *pool = tc->pool;
> > - unsigned long flags;
> > struct list_head cells;
> > struct dm_bio_prison_cell *cell, *tmp;
> >
> > INIT_LIST_HEAD(&cells);
> >
> > - spin_lock_irqsave(&tc->lock, flags);
> > + spin_lock_irq(&tc->lock);
> > list_splice_init(&tc->deferred_cells, &cells);
> > - spin_unlock_irqrestore(&tc->lock, flags);
> > + spin_unlock_irq(&tc->lock);
> >
> > list_for_each_entry_safe(cell, tmp, &cells, user_list)
> > cell_requeue(pool, cell);
> > @@ -640,14 +638,13 @@ static void requeue_deferred_cells(struc
> > static void requeue_io(struct thin_c *tc)
> > {
> > struct bio_list bios;
> > - unsigned long flags;
> >
> > bio_list_init(&bios);
> >
> > - spin_lock_irqsave(&tc->lock, flags);
> > + spin_lock_irq(&tc->lock);
> > __merge_bio_list(&bios, &tc->deferred_bio_list);
> > __merge_bio_list(&bios, &tc->retry_on_resume_list);
> > - spin_unlock_irqrestore(&tc->lock, flags);
> > + spin_unlock_irq(&tc->lock);
> >
> > error_bio_list(&bios, BLK_STS_DM_REQUEUE);
> > requeue_deferred_cells(tc);
> > @@ -756,7 +753,6 @@ static void inc_all_io_entry(struct pool
> > static void issue(struct thin_c *tc, struct bio *bio)
> > {
> > struct pool *pool = tc->pool;
> > - unsigned long flags;
> >
> > if (!bio_triggers_commit(tc, bio)) {
> > generic_make_request(bio);
> > @@ -777,9 +773,9 @@ static void issue(struct thin_c *tc, str
> > * Batch together any bios that trigger commits and then issue a
> > * single commit for them in process_deferred_bios().
> > */
> > - spin_lock_irqsave(&pool->lock, flags);
> > + spin_lock_irq(&pool->lock);
> > bio_list_add(&pool->deferred_flush_bios, bio);
> > - spin_unlock_irqrestore(&pool->lock, flags);
> > + spin_unlock_irq(&pool->lock);
> > }
> >
> > static void remap_to_origin_and_issue(struct thin_c *tc, struct bio *bio)
> > @@ -960,7 +956,6 @@ static void process_prepared_mapping_fai
> > static void complete_overwrite_bio(struct thin_c *tc, struct bio *bio)
> > {
> > struct pool *pool = tc->pool;
> > - unsigned long flags;
> >
> > /*
> > * If the bio has the REQ_FUA flag set we must commit the metadata
> > @@ -985,9 +980,9 @@ static void complete_overwrite_bio(struc
> > * Batch together any bios that trigger commits and then issue a
> > * single commit for them in process_deferred_bios().
> > */
> > - spin_lock_irqsave(&pool->lock, flags);
> > + spin_lock_irq(&pool->lock);
> > bio_list_add(&pool->deferred_flush_completions, bio);
> > - spin_unlock_irqrestore(&pool->lock, flags);
> > + spin_unlock_irq(&pool->lock);
> > }
> >
> > static void process_prepared_mapping(struct dm_thin_new_mapping *m)
> > @@ -1226,14 +1221,13 @@ static void process_prepared_discard_pas
> > static void process_prepared(struct pool *pool, struct list_head *head,
> > process_mapping_fn *fn)
> > {
> > - unsigned long flags;
> > struct list_head maps;
> > struct dm_thin_new_mapping *m, *tmp;
> >
> > INIT_LIST_HEAD(&maps);
> > - spin_lock_irqsave(&pool->lock, flags);
> > + spin_lock_irq(&pool->lock);
> > list_splice_init(head, &maps);
> > - spin_unlock_irqrestore(&pool->lock, flags);
> > + spin_unlock_irq(&pool->lock);
> >
> > list_for_each_entry_safe(m, tmp, &maps, list)
> > (*fn)(m);
> > @@ -1510,14 +1504,12 @@ static int commit(struct pool *pool)
> >
> > static void check_low_water_mark(struct pool *pool, dm_block_t free_blocks)
> > {
> > - unsigned long flags;
> > -
> > if (free_blocks <= pool->low_water_blocks && !pool->low_water_triggered) {
> > DMWARN("%s: reached low water mark for data device: sending event.",
> > dm_device_name(pool->pool_md));
> > - spin_lock_irqsave(&pool->lock, flags);
> > + spin_lock_irq(&pool->lock);
> > pool->low_water_triggered = true;
> > - spin_unlock_irqrestore(&pool->lock, flags);
> > + spin_unlock_irq(&pool->lock);
> > dm_table_event(pool->ti->table);
> > }
> > }
> > @@ -1593,11 +1585,10 @@ static void retry_on_resume(struct bio *
> > {
> > struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
> > struct thin_c *tc = h->tc;
> > - unsigned long flags;
> >
> > - spin_lock_irqsave(&tc->lock, flags);
> > + spin_lock_irq(&tc->lock);
> > bio_list_add(&tc->retry_on_resume_list, bio);
> > - spin_unlock_irqrestore(&tc->lock, flags);
> > + spin_unlock_irq(&tc->lock);
> > }
> >
> > static blk_status_t should_error_unserviceable_bio(struct pool *pool)
> > @@ -2170,7 +2161,6 @@ static void __sort_thin_deferred_bios(st
> > static void process_thin_deferred_bios(struct thin_c *tc)
> > {
> > struct pool *pool = tc->pool;
> > - unsigned long flags;
> > struct bio *bio;
> > struct bio_list bios;
> > struct blk_plug plug;
> > @@ -2184,10 +2174,10 @@ static void process_thin_deferred_bios(s
> >
> > bio_list_init(&bios);
> >
> > - spin_lock_irqsave(&tc->lock, flags);
> > + spin_lock_irq(&tc->lock);
> >
> > if (bio_list_empty(&tc->deferred_bio_list)) {
> > - spin_unlock_irqrestore(&tc->lock, flags);
> > + spin_unlock_irq(&tc->lock);
> > return;
> > }
> >
> > @@ -2196,7 +2186,7 @@ static void process_thin_deferred_bios(s
> > bio_list_merge(&bios, &tc->deferred_bio_list);
> > bio_list_init(&tc->deferred_bio_list);
> >
> > - spin_unlock_irqrestore(&tc->lock, flags);
> > + spin_unlock_irq(&tc->lock);
> >
> > blk_start_plug(&plug);
> > while ((bio = bio_list_pop(&bios))) {
> > @@ -2206,10 +2196,10 @@ static void process_thin_deferred_bios(s
> > * prepared mappings to process.
> > */
> > if (ensure_next_mapping(pool)) {
> > - spin_lock_irqsave(&tc->lock, flags);
> > + spin_lock_irq(&tc->lock);
> > bio_list_add(&tc->deferred_bio_list, bio);
> > bio_list_merge(&tc->deferred_bio_list, &bios);
> > - spin_unlock_irqrestore(&tc->lock, flags);
> > + spin_unlock_irq(&tc->lock);
> > break;
> > }
> >
> > @@ -2264,16 +2254,15 @@ static unsigned sort_cells(struct pool *
> > static void process_thin_deferred_cells(struct thin_c *tc)
> > {
> > struct pool *pool = tc->pool;
> > - unsigned long flags;
> > struct list_head cells;
> > struct dm_bio_prison_cell *cell;
> > unsigned i, j, count;
> >
> > INIT_LIST_HEAD(&cells);
> >
> > - spin_lock_irqsave(&tc->lock, flags);
> > + spin_lock_irq(&tc->lock);
> > list_splice_init(&tc->deferred_cells, &cells);
> > - spin_unlock_irqrestore(&tc->lock, flags);
> > + spin_unlock_irq(&tc->lock);
> >
> > if (list_empty(&cells))
> > return;
> > @@ -2294,9 +2283,9 @@ static void process_thin_deferred_cells(
> > for (j = i; j < count; j++)
> > list_add(&pool->cell_sort_array[j]->user_list, &cells);
> >
> > - spin_lock_irqsave(&tc->lock, flags);
> > + spin_lock_irq(&tc->lock);
> > list_splice(&cells, &tc->deferred_cells);
> > - spin_unlock_irqrestore(&tc->lock, flags);
> > + spin_unlock_irq(&tc->lock);
> > return;
> > }
> >
> > @@ -2349,7 +2338,6 @@ static struct thin_c *get_next_thin(stru
> >
> > static void process_deferred_bios(struct pool *pool)
> > {
> > - unsigned long flags;
> > struct bio *bio;
> > struct bio_list bios, bio_completions;
> > struct thin_c *tc;
> > @@ -2368,13 +2356,13 @@ static void process_deferred_bios(struct
> > bio_list_init(&bios);
> > bio_list_init(&bio_completions);
> >
> > - spin_lock_irqsave(&pool->lock, flags);
> > + spin_lock_irq(&pool->lock);
> > bio_list_merge(&bios, &pool->deferred_flush_bios);
> > bio_list_init(&pool->deferred_flush_bios);
> >
> > bio_list_merge(&bio_completions, &pool->deferred_flush_completions);
> > bio_list_init(&pool->deferred_flush_completions);
> > - spin_unlock_irqrestore(&pool->lock, flags);
> > + spin_unlock_irq(&pool->lock);
> >
> > if (bio_list_empty(&bios) && bio_list_empty(&bio_completions) &&
> > !(dm_pool_changed_this_transaction(pool->pmd) && need_commit_due_to_time(pool)))
> > @@ -2657,12 +2645,11 @@ static void metadata_operation_failed(st
> > */
> > static void thin_defer_bio(struct thin_c *tc, struct bio *bio)
> > {
> > - unsigned long flags;
> > struct pool *pool = tc->pool;
> >
> > - spin_lock_irqsave(&tc->lock, flags);
> > + spin_lock_irq(&tc->lock);
> > bio_list_add(&tc->deferred_bio_list, bio);
> > - spin_unlock_irqrestore(&tc->lock, flags);
> > + spin_unlock_irq(&tc->lock);
> >
> > wake_worker(pool);
> > }
> > @@ -2678,13 +2665,12 @@ static void thin_defer_bio_with_throttle
> >
> > static void thin_defer_cell(struct thin_c *tc, struct dm_bio_prison_cell *cell)
> > {
> > - unsigned long flags;
> > struct pool *pool = tc->pool;
> >
> > throttle_lock(&pool->throttle);
> > - spin_lock_irqsave(&tc->lock, flags);
> > + spin_lock_irq(&tc->lock);
> > list_add_tail(&cell->user_list, &tc->deferred_cells);
> > - spin_unlock_irqrestore(&tc->lock, flags);
> > + spin_unlock_irq(&tc->lock);
> > throttle_unlock(&pool->throttle);
> >
> > wake_worker(pool);
> > @@ -2810,15 +2796,14 @@ static int pool_is_congested(struct dm_t
> >
> > static void requeue_bios(struct pool *pool)
> > {
> > - unsigned long flags;
> > struct thin_c *tc;
> >
> > rcu_read_lock();
> > list_for_each_entry_rcu(tc, &pool->active_thins, list) {
> > - spin_lock_irqsave(&tc->lock, flags);
> > + spin_lock_irq(&tc->lock);
> > bio_list_merge(&tc->deferred_bio_list, &tc->retry_on_resume_list);
> > bio_list_init(&tc->retry_on_resume_list);
> > - spin_unlock_irqrestore(&tc->lock, flags);
> > + spin_unlock_irq(&tc->lock);
> > }
> > rcu_read_unlock();
> > }
> > @@ -3412,15 +3397,14 @@ static int pool_map(struct dm_target *ti
> > int r;
> > struct pool_c *pt = ti->private;
> > struct pool *pool = pt->pool;
> > - unsigned long flags;
> >
> > /*
> > * As this is a singleton target, ti->begin is always zero.
> > */
> > - spin_lock_irqsave(&pool->lock, flags);
> > + spin_lock_irq(&pool->lock);
> > bio_set_dev(bio, pt->data_dev->bdev);
> > r = DM_MAPIO_REMAPPED;
> > - spin_unlock_irqrestore(&pool->lock, flags);
> > + spin_unlock_irq(&pool->lock);
> >
> > return r;
> > }
> > @@ -3591,7 +3575,6 @@ static void pool_resume(struct dm_target
> > {
> > struct pool_c *pt = ti->private;
> > struct pool *pool = pt->pool;
> > - unsigned long flags;
> >
> > /*
> > * Must requeue active_thins' bios and then resume
> > @@ -3600,10 +3583,10 @@ static void pool_resume(struct dm_target
> > requeue_bios(pool);
> > pool_resume_active_thins(pool);
> >
> > - spin_lock_irqsave(&pool->lock, flags);
> > + spin_lock_irq(&pool->lock);
> > pool->low_water_triggered = false;
> > pool->suspended = false;
> > - spin_unlock_irqrestore(&pool->lock, flags);
> > + spin_unlock_irq(&pool->lock);
> >
> > do_waker(&pool->waker.work);
> > }
> > @@ -3612,11 +3595,10 @@ static void pool_presuspend(struct dm_ta
> > {
> > struct pool_c *pt = ti->private;
> > struct pool *pool = pt->pool;
> > - unsigned long flags;
> >
> > - spin_lock_irqsave(&pool->lock, flags);
> > + spin_lock_irq(&pool->lock);
> > pool->suspended = true;
> > - spin_unlock_irqrestore(&pool->lock, flags);
> > + spin_unlock_irq(&pool->lock);
> >
> > pool_suspend_active_thins(pool);
> > }
> > @@ -3625,13 +3607,12 @@ static void pool_presuspend_undo(struct
> > {
> > struct pool_c *pt = ti->private;
> > struct pool *pool = pt->pool;
> > - unsigned long flags;
> >
> > pool_resume_active_thins(pool);
> >
> > - spin_lock_irqsave(&pool->lock, flags);
> > + spin_lock_irq(&pool->lock);
> > pool->suspended = false;
> > - spin_unlock_irqrestore(&pool->lock, flags);
> > + spin_unlock_irq(&pool->lock);
> > }
> >
> > static void pool_postsuspend(struct dm_target *ti)
> > @@ -4110,11 +4091,10 @@ static void thin_put(struct thin_c *tc)
> > static void thin_dtr(struct dm_target *ti)
> > {
> > struct thin_c *tc = ti->private;
> > - unsigned long flags;
> >
> > - spin_lock_irqsave(&tc->pool->lock, flags);
> > + spin_lock_irq(&tc->pool->lock);
> > list_del_rcu(&tc->list);
> > - spin_unlock_irqrestore(&tc->pool->lock, flags);
> > + spin_unlock_irq(&tc->pool->lock);
> > synchronize_rcu();
> >
> > thin_put(tc);
> > @@ -4150,7 +4130,6 @@ static int thin_ctr(struct dm_target *ti
> > struct thin_c *tc;
> > struct dm_dev *pool_dev, *origin_dev;
> > struct mapped_device *pool_md;
> > - unsigned long flags;
> >
> > mutex_lock(&dm_thin_pool_table.mutex);
> >
> > @@ -4244,9 +4223,9 @@ static int thin_ctr(struct dm_target *ti
> >
> > mutex_unlock(&dm_thin_pool_table.mutex);
> >
> > - spin_lock_irqsave(&tc->pool->lock, flags);
> > + spin_lock_irq(&tc->pool->lock);
> > if (tc->pool->suspended) {
> > - spin_unlock_irqrestore(&tc->pool->lock, flags);
> > + spin_unlock_irq(&tc->pool->lock);
> > mutex_lock(&dm_thin_pool_table.mutex); /* reacquire for __pool_dec */
> > ti->error = "Unable to activate thin device while pool is suspended";
> > r = -EINVAL;
> > @@ -4255,7 +4234,7 @@ static int thin_ctr(struct dm_target *ti
> > refcount_set(&tc->refcount, 1);
> > init_completion(&tc->can_destroy);
> > list_add_tail_rcu(&tc->list, &tc->pool->active_thins);
> > - spin_unlock_irqrestore(&tc->pool->lock, flags);
> > + spin_unlock_irq(&tc->pool->lock);
> > /*
> > * This synchronize_rcu() call is needed here otherwise we risk a
> > * wake_worker() call finding no bios to process (because the newly
> >
> > --
> > dm-devel mailing list
> > dm-devel@xxxxxxxxxx
> > https://www.redhat.com/mailman/listinfo/dm-devel
> >
>
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