dm-verity: remove useless mempool

v->fec->extra_pool has zero reserved entries, so we can remove it and use
the kernel cache directly.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Eric Biggers <ebiggers@kernel.org>

Author: Mikulas Patocka

drivers/md/dm-verity-fec.c

@@ -333,7 +333,7 @@ static int fec_alloc_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio)
 		if (fio->bufs[n])
 			continue;
 
-		fio->bufs[n] = mempool_alloc(&v->fec->extra_pool, GFP_NOWAIT);
+		fio->bufs[n] = kmem_cache_alloc(v->fec->cache, GFP_NOWAIT);
 		/* we can manage with even one buffer if necessary */
 		if (unlikely(!fio->bufs[n]))
 			break;
@@ -482,7 +482,8 @@ void verity_fec_finish_io(struct dm_verity_io *io)
 		mempool_free(fio->bufs[n], &f->prealloc_pool);
 
 	fec_for_each_extra_buffer(fio, n)
-		mempool_free(fio->bufs[n], &f->extra_pool);
+		if (fio->bufs[n])
+			kmem_cache_free(f->cache, fio->bufs[n]);
 
 	mempool_free(fio->output, &f->output_pool);
 }
@@ -534,7 +535,6 @@ void verity_fec_dtr(struct dm_verity *v)
 
 	mempool_exit(&f->rs_pool);
 	mempool_exit(&f->prealloc_pool);
-	mempool_exit(&f->extra_pool);
 	mempool_exit(&f->output_pool);
 	kmem_cache_destroy(f->cache);
 
@@ -787,12 +787,6 @@ int verity_fec_ctr(struct dm_verity *v)
 		return ret;
 	}
 
-	ret = mempool_init_slab_pool(&f->extra_pool, 0, f->cache);
-	if (ret) {
-		ti->error = "Cannot allocate FEC buffer extra pool";
-		return ret;
-	}
-
 	/* Preallocate an output buffer for each thread */
 	ret = mempool_init_kmalloc_pool(&f->output_pool, num_online_cpus(),
 					1 << v->data_dev_block_bits);

drivers/md/dm-verity-fec.h

@@ -42,7 +42,6 @@ struct dm_verity_fec {
 	unsigned char rsn;	/* N of RS(M, N) */
 	mempool_t rs_pool;	/* mempool for fio->rs */
 	mempool_t prealloc_pool;	/* mempool for preallocated buffers */
-	mempool_t extra_pool;	/* mempool for extra buffers */
 	mempool_t output_pool;	/* mempool for output */
 	struct kmem_cache *cache;	/* cache for buffers */
 	atomic64_t corrected; /* corrected errors */