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
>
> 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
>
> --
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>
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