lightnvm: pblk: allocate line map bitmaps using a mempool

Line map bitmap allocations are fairly large and can fail. Allocation
failures are fatal to pblk, stopping the write pipeline. To avoid this,
allocate the bitmaps using a mempool instead.

Mempool allocations never fail if called from a process context,
and pblk *should* only allocate map bitmaps in process context,
but keep the failure handling for robustness sake.

Signed-off-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/lightnvm/pblk-core.c

@@ -1049,15 +1049,18 @@ static int pblk_line_init_metadata(struct pblk *pblk, struct pblk_line *line,
 static int pblk_line_alloc_bitmaps(struct pblk *pblk, struct pblk_line *line)
 {
 	struct pblk_line_meta *lm = &pblk->lm;
+	struct pblk_line_mgmt *l_mg = &pblk->l_mg;
 
-	line->map_bitmap = kzalloc(lm->sec_bitmap_len, GFP_KERNEL);
+	line->map_bitmap = mempool_alloc(l_mg->bitmap_pool, GFP_KERNEL);
 	if (!line->map_bitmap)
 		return -ENOMEM;
 
+	memset(line->map_bitmap, 0, lm->sec_bitmap_len);
+
 	/* will be initialized using bb info from map_bitmap */
-	line->invalid_bitmap = kmalloc(lm->sec_bitmap_len, GFP_KERNEL);
+	line->invalid_bitmap = mempool_alloc(l_mg->bitmap_pool, GFP_KERNEL);
 	if (!line->invalid_bitmap) {
-		kfree(line->map_bitmap);
+		mempool_free(line->map_bitmap, l_mg->bitmap_pool);
 		line->map_bitmap = NULL;
 		return -ENOMEM;
 	}
@@ -1243,7 +1246,9 @@ int pblk_line_recov_alloc(struct pblk *pblk, struct pblk_line *line)
 
 void pblk_line_recov_close(struct pblk *pblk, struct pblk_line *line)
 {
-	kfree(line->map_bitmap);
+	struct pblk_line_mgmt *l_mg = &pblk->l_mg;
+
+	mempool_free(line->map_bitmap, l_mg->bitmap_pool);
 	line->map_bitmap = NULL;
 	line->smeta = NULL;
 	line->emeta = NULL;
@@ -1261,8 +1266,11 @@ static void pblk_line_reinit(struct pblk_line *line)
 
 void pblk_line_free(struct pblk_line *line)
 {
-	kfree(line->map_bitmap);
-	kfree(line->invalid_bitmap);
+	struct pblk *pblk = line->pblk;
+	struct pblk_line_mgmt *l_mg = &pblk->l_mg;
+
+	mempool_free(line->map_bitmap, l_mg->bitmap_pool);
+	mempool_free(line->invalid_bitmap, l_mg->bitmap_pool);
 
 	pblk_line_reinit(line);
 }
@@ -1741,7 +1749,7 @@ void pblk_line_close(struct pblk *pblk, struct pblk_line *line)
 
 	list_add_tail(&line->list, move_list);
 
-	kfree(line->map_bitmap);
+	mempool_free(line->map_bitmap, l_mg->bitmap_pool);
 	line->map_bitmap = NULL;
 	line->smeta = NULL;
 	line->emeta = NULL;

drivers/lightnvm/pblk-init.c

@@ -498,6 +498,9 @@ static void pblk_line_mg_free(struct pblk *pblk)
 		pblk_mfree(l_mg->eline_meta[i]->buf, l_mg->emeta_alloc_type);
 		kfree(l_mg->eline_meta[i]);
 	}
+
+	mempool_destroy(l_mg->bitmap_pool);
+	kmem_cache_destroy(l_mg->bitmap_cache);
 }
 
 static void pblk_line_meta_free(struct pblk_line_mgmt *l_mg,
@@ -797,6 +800,17 @@ static int pblk_line_mg_init(struct pblk *pblk)
 			goto fail_free_smeta;
 	}
 
+	l_mg->bitmap_cache = kmem_cache_create("pblk_lm_bitmap",
+			lm->sec_bitmap_len, 0, 0, NULL);
+	if (!l_mg->bitmap_cache)
+		goto fail_free_smeta;
+
+	/* the bitmap pool is used for both valid and map bitmaps */
+	l_mg->bitmap_pool = mempool_create_slab_pool(PBLK_DATA_LINES * 2,
+				l_mg->bitmap_cache);
+	if (!l_mg->bitmap_pool)
+		goto fail_destroy_bitmap_cache;
+
 	/* emeta allocates three different buffers for managing metadata with
 	 * in-memory and in-media layouts
 	 */
@@ -849,6 +863,10 @@ fail_free_emeta:
 			kfree(l_mg->eline_meta[i]->buf);
 		kfree(l_mg->eline_meta[i]);
 	}
+
+	mempool_destroy(l_mg->bitmap_pool);
+fail_destroy_bitmap_cache:
+	kmem_cache_destroy(l_mg->bitmap_cache);
 fail_free_smeta:
 	for (i = 0; i < PBLK_DATA_LINES; i++)
 		kfree(l_mg->sline_meta[i]);

drivers/lightnvm/pblk-recovery.c

@@ -939,7 +939,7 @@ next:
 			list_move_tail(&line->list, move_list);
 			spin_unlock(&l_mg->gc_lock);
 
-			kfree(line->map_bitmap);
+			mempool_free(line->map_bitmap, l_mg->bitmap_pool);
 			line->map_bitmap = NULL;
 			line->smeta = NULL;
 			line->emeta = NULL;

drivers/lightnvm/pblk.h

@@ -530,6 +530,10 @@ struct pblk_line_mgmt {
 	struct pblk_emeta *eline_meta[PBLK_DATA_LINES];
 	unsigned long meta_bitmap;
 
+	/* Cache and mempool for map/invalid bitmaps */
+	struct kmem_cache *bitmap_cache;
+	mempool_t *bitmap_pool;
+
 	/* Helpers for fast bitmap calculations */
 	unsigned long *bb_template;
 	unsigned long *bb_aux;