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dm kcopyd: alloc pages from the main page allocator 

This patch changes dm-kcopyd so that it allocates pages from the main
page allocator with __GFP_NOWARN | __GFP_NORETRY flags (so that it can
fail in case of memory pressure). If the allocation fails, dm-kcopyd
allocates pages from its own reserve.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Mikulas Patocka 2011-05-29 13:03:07 +01:00 committed by Alasdair G Kergon
parent f99b55eec7
commit d04714580f
1 changed files with 60 additions and 31 deletions
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89
drivers/md/dm-kcopyd.c
View File

@ -37,8 +37,8 @@
*---------------------------------------------------------------*/
struct dm_kcopyd_client {
struct page_list *pages;
unsigned int nr_pages;
unsigned int nr_free_pages;
unsigned nr_reserved_pages;
unsigned nr_free_pages;
struct dm_io_client *io_client;
@ -70,6 +70,9 @@ static void wake(struct dm_kcopyd_client *kc)
queue_work(kc->kcopyd_wq, &kc->kcopyd_work);
}
/*
* Obtain one page for the use of kcopyd.
*/
static struct page_list *alloc_pl(gfp_t gfp)
{
struct page_list *pl;
@ -93,34 +96,56 @@ static void free_pl(struct page_list *pl)
kfree(pl);
}
/*
* Add the provided pages to a client's free page list, releasing
* back to the system any beyond the reserved_pages limit.
*/
static void kcopyd_put_pages(struct dm_kcopyd_client *kc, struct page_list *pl)
{
struct page_list *next;
do {
next = pl->next;
if (kc->nr_free_pages >= kc->nr_reserved_pages)
free_pl(pl);
else {
pl->next = kc->pages;
kc->pages = pl;
kc->nr_free_pages++;
}
pl = next;
} while (pl);
}
static int kcopyd_get_pages(struct dm_kcopyd_client *kc,
unsigned int nr, struct page_list **pages)
{
struct page_list *pl;
if (kc->nr_free_pages < nr)
return -ENOMEM;
kc->nr_free_pages -= nr;
for (*pages = pl = kc->pages; --nr; pl = pl->next)
;
*pages = NULL;
do {
pl = alloc_pl(__GFP_NOWARN | __GFP_NORETRY);
if (unlikely(!pl)) {
/* Use reserved pages */
pl = kc->pages;
if (unlikely(!pl))
goto out_of_memory;
kc->pages = pl->next;
pl->next = NULL;
kc->nr_free_pages--;
}
pl->next = *pages;
*pages = pl;
} while (--nr);
return 0;
}
static void kcopyd_put_pages(struct dm_kcopyd_client *kc, struct page_list *pl)
{
struct page_list *cursor;
for (cursor = pl; cursor->next; cursor = cursor->next)
kc->nr_free_pages++;
kc->nr_free_pages++;
cursor->next = kc->pages;
kc->pages = pl;
out_of_memory:
if (*pages)
kcopyd_put_pages(kc, *pages);
return -ENOMEM;
}
/*
@ -137,12 +162,15 @@ static void drop_pages(struct page_list *pl)
}
}
static int client_alloc_pages(struct dm_kcopyd_client *kc, unsigned int nr)
/*
* Allocate and reserve nr_pages for the use of a specific client.
*/
static int client_reserve_pages(struct dm_kcopyd_client *kc, unsigned nr_pages)
{
unsigned int i;
unsigned i;
struct page_list *pl = NULL, *next;
for (i = 0; i < nr; i++) {
for (i = 0; i < nr_pages; i++) {
next = alloc_pl(GFP_KERNEL);
if (!next) {
if (pl)
@ -153,17 +181,18 @@ static int client_alloc_pages(struct dm_kcopyd_client *kc, unsigned int nr)
pl = next;
}
kc->nr_reserved_pages += nr_pages;
kcopyd_put_pages(kc, pl);
kc->nr_pages += nr;
return 0;
}
static void client_free_pages(struct dm_kcopyd_client *kc)
{
BUG_ON(kc->nr_free_pages != kc->nr_pages);
BUG_ON(kc->nr_free_pages != kc->nr_reserved_pages);
drop_pages(kc->pages);
kc->pages = NULL;
kc->nr_free_pages = kc->nr_pages = 0;
kc->nr_free_pages = kc->nr_reserved_pages = 0;
}
/*-----------------------------------------------------------------
@ -607,7 +636,7 @@ int kcopyd_cancel(struct kcopyd_job *job, int block)
/*-----------------------------------------------------------------
* Client setup
*---------------------------------------------------------------*/
int dm_kcopyd_client_create(unsigned int nr_pages,
int dm_kcopyd_client_create(unsigned min_pages,
struct dm_kcopyd_client **result)
{
int r = -ENOMEM;
@ -633,12 +662,12 @@ int dm_kcopyd_client_create(unsigned int nr_pages,
goto bad_workqueue;
kc->pages = NULL;
kc->nr_pages = kc->nr_free_pages = 0;
r = client_alloc_pages(kc, nr_pages);
kc->nr_reserved_pages = kc->nr_free_pages = 0;
r = client_reserve_pages(kc, min_pages);
if (r)
goto bad_client_pages;
kc->io_client = dm_io_client_create(nr_pages);
kc->io_client = dm_io_client_create(min_pages);
if (IS_ERR(kc->io_client)) {
r = PTR_ERR(kc->io_client);
goto bad_io_client;