diff options
| author | Mikulas Patocka <mpatocka@redhat.com> | 2011-05-29 13:03:02 +0100 |
|---|---|---|
| committer | Alasdair G Kergon <agk@redhat.com> | 2011-05-29 13:03:02 +0100 |
| commit | 4cc1b4cffd187a5c5d6264c8d766c49b3c57fb05 (patch) | |
| tree | 98b550b7e3c00fcdf20cc8b0a9c5b9478cb45ac9 | |
| parent | c6ea41fbbe08f270a8edef99dc369faf809d1bd6 (diff) | |
dm kcopyd: remove superfluous page allocation spinlock
Remove the spinlock protecting the pages allocation. The spinlock is only
taken on initialization or from single-threaded workqueue. Therefore, the
spinlock is useless.
The spinlock is taken in kcopyd_get_pages and kcopyd_put_pages.
kcopyd_get_pages is only called from run_pages_job, which is only
called from process_jobs called from do_work.
kcopyd_put_pages is called from client_alloc_pages (which is initialization
function) or from run_complete_job. run_complete_job is only called from
process_jobs called from do_work.
Another spinlock, kc->job_lock is taken each time someone pushes or pops
some work for the worker thread. Once we take kc->job_lock, we
guarantee that any written memory is visible to the other CPUs.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
| -rw-r--r-- | drivers/md/dm-kcopyd.c | 11 |
1 files changed, 1 insertions, 10 deletions
diff --git a/drivers/md/dm-kcopyd.c b/drivers/md/dm-kcopyd.c index 24fb42ed7b8..ed957791639 100644 --- a/drivers/md/dm-kcopyd.c +++ b/drivers/md/dm-kcopyd.c @@ -36,7 +36,6 @@ * pages for kcopyd io. *---------------------------------------------------------------*/ struct dm_kcopyd_client { - spinlock_t lock; struct page_list *pages; unsigned int nr_pages; unsigned int nr_free_pages; @@ -99,11 +98,8 @@ static int kcopyd_get_pages(struct dm_kcopyd_client *kc, { struct page_list *pl; - spin_lock(&kc->lock); - if (kc->nr_free_pages < nr) { - spin_unlock(&kc->lock); + if (kc->nr_free_pages < nr) return -ENOMEM; - } kc->nr_free_pages -= nr; for (*pages = pl = kc->pages; --nr; pl = pl->next) @@ -112,8 +108,6 @@ static int kcopyd_get_pages(struct dm_kcopyd_client *kc, kc->pages = pl->next; pl->next = NULL; - spin_unlock(&kc->lock); - return 0; } @@ -121,14 +115,12 @@ static void kcopyd_put_pages(struct dm_kcopyd_client *kc, struct page_list *pl) { struct page_list *cursor; - spin_lock(&kc->lock); for (cursor = pl; cursor->next; cursor = cursor->next) kc->nr_free_pages++; kc->nr_free_pages++; cursor->next = kc->pages; kc->pages = pl; - spin_unlock(&kc->lock); } /* @@ -625,7 +617,6 @@ int dm_kcopyd_client_create(unsigned int nr_pages, if (!kc) return -ENOMEM; - spin_lock_init(&kc->lock); spin_lock_init(&kc->job_lock); INIT_LIST_HEAD(&kc->complete_jobs); INIT_LIST_HEAD(&kc->io_jobs); |