ceph: move to a dedicated slabcache for mds requests

On my machine (x86_64) this struct is 952 bytes, which gets rounded up
to 1024 by kmalloc. Move this to a dedicated slabcache, so we can
allocate them without the extra 72 bytes of overhead per.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/mds_client.c

@@ -736,7 +736,7 @@ void ceph_mdsc_release_request(struct kref *kref)
 	put_request_session(req);
 	ceph_unreserve_caps(req->r_mdsc, &req->r_caps_reservation);
 	WARN_ON_ONCE(!list_empty(&req->r_wait));
-	kfree(req);
+	kmem_cache_free(ceph_mds_request_cachep, req);
 }
 
 DEFINE_RB_FUNCS(request, struct ceph_mds_request, r_tid, r_node)
@@ -2094,8 +2094,9 @@ int ceph_alloc_readdir_reply_buffer(struct ceph_mds_request *req,
 struct ceph_mds_request *
 ceph_mdsc_create_request(struct ceph_mds_client *mdsc, int op, int mode)
 {
-	struct ceph_mds_request *req = kzalloc(sizeof(*req), GFP_NOFS);
+	struct ceph_mds_request *req;
 
+	req = kmem_cache_zalloc(ceph_mds_request_cachep, GFP_NOFS);
 	if (!req)
 		return ERR_PTR(-ENOMEM);
 

fs/ceph/super.c

@@ -729,6 +729,7 @@ struct kmem_cache *ceph_cap_flush_cachep;
 struct kmem_cache *ceph_dentry_cachep;
 struct kmem_cache *ceph_file_cachep;
 struct kmem_cache *ceph_dir_file_cachep;
+struct kmem_cache *ceph_mds_request_cachep;
 
 static void ceph_inode_init_once(void *foo)
 {
@@ -769,6 +770,10 @@ static int __init init_caches(void)
 	if (!ceph_dir_file_cachep)
 		goto bad_dir_file;
 
+	ceph_mds_request_cachep = KMEM_CACHE(ceph_mds_request, SLAB_MEM_SPREAD);
+	if (!ceph_mds_request_cachep)
+		goto bad_mds_req;
+
 	error = ceph_fscache_register();
 	if (error)
 		goto bad_fscache;
@@ -776,6 +781,8 @@ static int __init init_caches(void)
 	return 0;
 
 bad_fscache:
+	kmem_cache_destroy(ceph_mds_request_cachep);
+bad_mds_req:
 	kmem_cache_destroy(ceph_dir_file_cachep);
 bad_dir_file:
 	kmem_cache_destroy(ceph_file_cachep);
@@ -804,6 +811,7 @@ static void destroy_caches(void)
 	kmem_cache_destroy(ceph_dentry_cachep);
 	kmem_cache_destroy(ceph_file_cachep);
 	kmem_cache_destroy(ceph_dir_file_cachep);
+	kmem_cache_destroy(ceph_mds_request_cachep);
 
 	ceph_fscache_unregister();
 }

include/linux/ceph/libceph.h

@@ -272,6 +272,7 @@ extern struct kmem_cache *ceph_cap_flush_cachep;
 extern struct kmem_cache *ceph_dentry_cachep;
 extern struct kmem_cache *ceph_file_cachep;
 extern struct kmem_cache *ceph_dir_file_cachep;
+extern struct kmem_cache *ceph_mds_request_cachep;
 
 /* ceph_common.c */
 extern bool libceph_compatible(void *data);