drbd: add page pool to be used for meta data IO

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

2 files changed, 31 insertions, 1 deletions

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 6586053429b..685ed4cca17 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -1496,11 +1496,32 @@ extern struct kmem_cache *drbd_al_ext_cache;	/* activity log extents */
 extern mempool_t *drbd_request_mempool;
 extern mempool_t *drbd_ee_mempool;
 
-extern struct page *drbd_pp_pool; /* drbd's page pool */
+/* drbd's page pool, used to buffer data received from the peer,
+ * or data requested by the peer.
+ *
+ * This does not have an emergency reserve.
+ *
+ * When allocating from this pool, it first takes pages from the pool.
+ * Only if the pool is depleted will try to allocate from the system.
+ *
+ * The assumption is that pages taken from this pool will be processed,
+ * and given back, "quickly", and then can be recycled, so we can avoid
+ * frequent calls to alloc_page(), and still will be able to make progress even
+ * under memory pressure.
+ */
+extern struct page *drbd_pp_pool;
 extern spinlock_t   drbd_pp_lock;
 extern int          drbd_pp_vacant;
 extern wait_queue_head_t drbd_pp_wait;
 
+/* We also need a standard (emergency-reserve backed) page pool
+ * for meta data IO (activity log, bitmap).
+ * We can keep it global, as long as it is used as "N pages at a time".
+ * 128 should be plenty, currently we probably can get away with as few as 1.
+ */
+#define DRBD_MIN_POOL_PAGES     128
+extern mempool_t *drbd_md_io_page_pool;
+
 extern rwlock_t global_state_lock;
 
 extern struct drbd_conf *drbd_new_device(unsigned int minor);
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index d830116781f..ed264c92c3a 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -139,6 +139,7 @@ struct kmem_cache *drbd_bm_ext_cache;	/* bitmap extents */
 struct kmem_cache *drbd_al_ext_cache;   /* activity log extents */
 mempool_t *drbd_request_mempool;
 mempool_t *drbd_ee_mempool;
+mempool_t *drbd_md_io_page_pool;
 
 /* I do not use a standard mempool, because:
    1) I want to hand out the pre-allocated objects first.
@@ -3264,6 +3265,8 @@ static void drbd_destroy_mempools(void)
 
         /* D_ASSERT(atomic_read(&drbd_pp_vacant)==0); */
 
+        if (drbd_md_io_page_pool)
+                mempool_destroy(drbd_md_io_page_pool);
         if (drbd_ee_mempool)
                 mempool_destroy(drbd_ee_mempool);
         if (drbd_request_mempool)
@@ -3277,6 +3280,7 @@ static void drbd_destroy_mempools(void)
         if (drbd_al_ext_cache)
                 kmem_cache_destroy(drbd_al_ext_cache);
 
+        drbd_md_io_page_pool = NULL;
         drbd_ee_mempool      = NULL;
         drbd_request_mempool = NULL;
         drbd_ee_cache        = NULL;
@@ -3300,6 +3304,7 @@ static int drbd_create_mempools(void)
         drbd_bm_ext_cache    = NULL;
         drbd_al_ext_cache    = NULL;
         drbd_pp_pool         = NULL;
+        drbd_md_io_page_pool = NULL;
 
         /* caches */
         drbd_request_cache = kmem_cache_create(
@@ -3323,6 +3328,10 @@ static int drbd_create_mempools(void)
                 goto Enomem;
 
         /* mempools */
+        drbd_md_io_page_pool = mempool_create_page_pool(DRBD_MIN_POOL_PAGES, 0);
+        if (drbd_md_io_page_pool == NULL)
+                goto Enomem;
+
         drbd_request_mempool = mempool_create(number,
                 mempool_alloc_slab, mempool_free_slab, drbd_request_cache);
         if (drbd_request_mempool == NULL)