lightnvm: pblk: do not use a mempool for line bitmaps

pblk holds two sector bitmaps: one to keep track of the mapped sectors
while the line is active and another one to keep track of the invalid
sectors. The latter is kept during the whole live of the line, until it
is recycled. Since we cannot guarantee forward progress for the mempool
in this case, get rid of the mempool and simply allocate memory through
kmalloc.

Reported-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/lightnvm/pblk-init.c

@@ -21,7 +21,7 @@
 #include "pblk.h"
 
 static struct kmem_cache *pblk_ws_cache, *pblk_rec_cache, *pblk_g_rq_cache,
-				*pblk_w_rq_cache, *pblk_line_meta_cache;
+				*pblk_w_rq_cache;
 static DECLARE_RWSEM(pblk_lock);
 struct bio_set *pblk_bio_set;
 
@@ -181,8 +181,6 @@ static int pblk_set_ppaf(struct pblk *pblk)
 
 static int pblk_init_global_caches(struct pblk *pblk)
 {
-	char cache_name[PBLK_CACHE_NAME_LEN];
-
 	down_write(&pblk_lock);
 	pblk_ws_cache = kmem_cache_create("pblk_blk_ws",
 				sizeof(struct pblk_line_ws), 0, 0, NULL);
@@ -217,19 +215,6 @@ static int pblk_init_global_caches(struct pblk *pblk)
 		up_write(&pblk_lock);
 		return -ENOMEM;
 	}
-
-	snprintf(cache_name, sizeof(cache_name), "pblk_line_m_%s",
-							pblk->disk->disk_name);
-	pblk_line_meta_cache = kmem_cache_create(cache_name,
-				pblk->lm.sec_bitmap_len, 0, 0, NULL);
-	if (!pblk_line_meta_cache) {
-		kmem_cache_destroy(pblk_ws_cache);
-		kmem_cache_destroy(pblk_rec_cache);
-		kmem_cache_destroy(pblk_g_rq_cache);
-		kmem_cache_destroy(pblk_w_rq_cache);
-		up_write(&pblk_lock);
-		return -ENOMEM;
-	}
 	up_write(&pblk_lock);
 
 	return 0;
@@ -276,16 +261,10 @@ static int pblk_core_init(struct pblk *pblk)
 	if (!pblk->w_rq_pool)
 		goto free_e_rq_pool;
 
-	pblk->line_meta_pool =
-			mempool_create_slab_pool(PBLK_META_POOL_SIZE,
-							pblk_line_meta_cache);
-	if (!pblk->line_meta_pool)
-		goto free_w_rq_pool;
-
 	pblk->close_wq = alloc_workqueue("pblk-close-wq",
 			WQ_MEM_RECLAIM | WQ_UNBOUND, PBLK_NR_CLOSE_JOBS);
 	if (!pblk->close_wq)
-		goto free_line_meta_pool;
+		goto free_w_rq_pool;
 
 	pblk->bb_wq = alloc_workqueue("pblk-bb-wq",
 			WQ_MEM_RECLAIM | WQ_UNBOUND, 0);
@@ -305,8 +284,6 @@ free_bb_wq:
 	destroy_workqueue(pblk->bb_wq);
 free_close_wq:
 	destroy_workqueue(pblk->close_wq);
-free_line_meta_pool:
-	mempool_destroy(pblk->line_meta_pool);
 free_w_rq_pool:
 	mempool_destroy(pblk->w_rq_pool);
 free_e_rq_pool:
@@ -336,13 +313,11 @@ static void pblk_core_free(struct pblk *pblk)
 	mempool_destroy(pblk->r_rq_pool);
 	mempool_destroy(pblk->e_rq_pool);
 	mempool_destroy(pblk->w_rq_pool);
-	mempool_destroy(pblk->line_meta_pool);
 
 	kmem_cache_destroy(pblk_ws_cache);
 	kmem_cache_destroy(pblk_rec_cache);
 	kmem_cache_destroy(pblk_g_rq_cache);
 	kmem_cache_destroy(pblk_w_rq_cache);
-	kmem_cache_destroy(pblk_line_meta_cache);
 }
 
 static void pblk_luns_free(struct pblk *pblk)