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Commit d0471458 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Alasdair G Kergon
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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: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent f99b55ee

drivers/md/dm-kcopyd.c

+60 −31
Original line number Diff line number Diff line
@@ -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;



	return 0;

			kc->nr_free_pages--;

		}

		pl->next = *pages;

		*pages = pl;

	} while (--nr);



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++;

	return 0;



	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;