Remove the spinlock protecting the pages allocation

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.

The spinlock is only taken on initialization or from single-threaded workqueue.
Therefore, the spinlock is useless.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

---
drivers/md/dm-kcopyd.c | 11 +----------
1 file changed, 1 insertion(+), 10 deletions(-)

Index: linux-2.6.39-rc7-fast/drivers/md/dm-kcopyd.c
================================================== =================
--- linux-2.6.39-rc7-fast.orig/drivers/md/dm-kcopyd.c 2011-05-18 18:17:35.000000000 +0200
+++ linux-2.6.39-rc7-fast/drivers/md/dm-kcopyd.c 2011-05-18 18:19:01.000000000 +0200
@@ -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_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_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_k
{
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);
}

/*
@@ -623,7 +615,6 @@ int dm_kcopyd_client_create(unsigned int
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);

--
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Remove the spinlock protecting the pages allocation

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.

The spinlock is only taken on initialization or from single-threaded workqueue.
Therefore, the spinlock is useless.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

---
drivers/md/dm-kcopyd.c | 11 +----------
1 file changed, 1 insertion(+), 10 deletions(-)

Index: linux-2.6.39-rc7-fast/drivers/md/dm-kcopyd.c
================================================== =================
--- linux-2.6.39-rc7-fast.orig/drivers/md/dm-kcopyd.c 2011-05-18 18:17:35.000000000 +0200
+++ linux-2.6.39-rc7-fast/drivers/md/dm-kcopyd.c 2011-05-18 18:19:01.000000000 +0200
@@ -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_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_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_k
{
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);
}

/*
@@ -623,7 +615,6 @@ int dm_kcopyd_client_create(unsigned int
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);

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