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>
diff --git a/drivers/md/dm-kcopyd.c b/drivers/md/dm-kcopyd.c
index 0270844..5dfbdcb 100644
--- a/drivers/md/dm-kcopyd.c
+++ b/drivers/md/dm-kcopyd.c
@@ -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 @@
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 @@
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;
+ *pages = NULL;
- kc->nr_free_pages -= nr;
- for (*pages = pl = kc->pages; --nr; pl = pl->next)
- ;
-
- kc->pages = pl->next;
- pl->next = 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;
+ 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 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 @@
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 @@
/*-----------------------------------------------------------------
* 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 @@
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;