cifs: Add mempools for cifs_io_request and cifs_io_subrequest structs

Add mempools for the allocation of cifs_io_request and cifs_io_subrequest
structs for netfslib to use so that it can guarantee eventual allocation in
writeback.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Steve French <sfrench@samba.org>
cc: Shyam Prasad N <nspmangalore@gmail.com>
cc: Rohith Surabattula <rohiths.msft@gmail.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cifs@vger.kernel.org
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org

fs/smb/client/cifsfs.c

@@ -371,9 +371,13 @@ static struct kmem_cache *cifs_inode_cachep;
 static struct kmem_cache *cifs_req_cachep;
 static struct kmem_cache *cifs_mid_cachep;
 static struct kmem_cache *cifs_sm_req_cachep;
+static struct kmem_cache *cifs_io_request_cachep;
+static struct kmem_cache *cifs_io_subrequest_cachep;
 mempool_t *cifs_sm_req_poolp;
 mempool_t *cifs_req_poolp;
 mempool_t *cifs_mid_poolp;
+mempool_t cifs_io_request_pool;
+mempool_t cifs_io_subrequest_pool;
 
 static struct inode *
 cifs_alloc_inode(struct super_block *sb)
@@ -1750,6 +1754,48 @@ static void destroy_mids(void)
 	kmem_cache_destroy(cifs_mid_cachep);
 }
 
+static int cifs_init_netfs(void)
+{
+	cifs_io_request_cachep =
+		kmem_cache_create("cifs_io_request",
+				  sizeof(struct netfs_io_request), 0,
+				  SLAB_HWCACHE_ALIGN, NULL);
+	if (!cifs_io_request_cachep)
+		goto nomem_req;
+
+	if (mempool_init_slab_pool(&cifs_io_request_pool, 100, cifs_io_request_cachep) < 0)
+		goto nomem_reqpool;
+
+	cifs_io_subrequest_cachep =
+		kmem_cache_create("cifs_io_subrequest",
+				  sizeof(struct cifs_io_subrequest), 0,
+				  SLAB_HWCACHE_ALIGN, NULL);
+	if (!cifs_io_subrequest_cachep)
+		goto nomem_subreq;
+
+	if (mempool_init_slab_pool(&cifs_io_subrequest_pool, 100, cifs_io_subrequest_cachep) < 0)
+		goto nomem_subreqpool;
+
+	return 0;
+
+nomem_subreqpool:
+	kmem_cache_destroy(cifs_io_subrequest_cachep);
+nomem_subreq:
+	mempool_destroy(&cifs_io_request_pool);
+nomem_reqpool:
+	kmem_cache_destroy(cifs_io_request_cachep);
+nomem_req:
+	return -ENOMEM;
+}
+
+static void cifs_destroy_netfs(void)
+{
+	mempool_destroy(&cifs_io_subrequest_pool);
+	kmem_cache_destroy(cifs_io_subrequest_cachep);
+	mempool_destroy(&cifs_io_request_pool);
+	kmem_cache_destroy(cifs_io_request_cachep);
+}
+
 static int __init
 init_cifs(void)
 {
@@ -1854,10 +1900,14 @@ init_cifs(void)
 	if (rc)
 		goto out_destroy_deferredclose_wq;
 
-	rc = init_mids();
+	rc = cifs_init_netfs();
 	if (rc)
 		goto out_destroy_inodecache;
 
+	rc = init_mids();
+	if (rc)
+		goto out_destroy_netfs;
+
 	rc = cifs_init_request_bufs();
 	if (rc)
 		goto out_destroy_mids;
@@ -1912,6 +1962,8 @@ out_destroy_request_bufs:
 	cifs_destroy_request_bufs();
 out_destroy_mids:
 	destroy_mids();
+out_destroy_netfs:
+	cifs_destroy_netfs();
 out_destroy_inodecache:
 	cifs_destroy_inodecache();
 out_destroy_deferredclose_wq:
@@ -1950,6 +2002,7 @@ exit_cifs(void)
 #endif
 	cifs_destroy_request_bufs();
 	destroy_mids();
+	cifs_destroy_netfs();
 	cifs_destroy_inodecache();
 	destroy_workqueue(deferredclose_wq);
 	destroy_workqueue(cifsoplockd_wq);

fs/smb/client/cifsglob.h

@@ -2094,6 +2094,8 @@ extern __u32 cifs_lock_secret;
 extern mempool_t *cifs_sm_req_poolp;
 extern mempool_t *cifs_req_poolp;
 extern mempool_t *cifs_mid_poolp;
+extern mempool_t cifs_io_request_pool;
+extern mempool_t cifs_io_subrequest_pool;
 
 /* Operations for different SMB versions */
 #define SMB1_VERSION_STRING	"1.0"