// SPDX-License-Identifier: GPL-2.0/* * linux/fs/nfs/cache_lib.c * * Helper routines for the NFS client caches * * Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@netapp.com> */#include <linux/kmod.h>#include <linux/module.h>#include <linux/moduleparam.h>#include <linux/mount.h>#include <linux/namei.h>#include <linux/slab.h>#include <linux/sunrpc/cache.h>#include <linux/sunrpc/rpc_pipe_fs.h>#include <net/net_namespace.h> #include "cache_lib.h" #define NFS_CACHE_UPCALL_PATHLEN 256#define NFS_CACHE_UPCALL_TIMEOUT 15 static char nfs_cache_getent_prog[NFS_CACHE_UPCALL_PATHLEN] =				"/sbin/nfs_cache_getent";static unsigned long nfs_cache_getent_timeout = NFS_CACHE_UPCALL_TIMEOUT; module_param_string(cache_getent, nfs_cache_getent_prog,		sizeof(nfs_cache_getent_prog), 0600);MODULE_PARM_DESC(cache_getent, "Path to the client cache upcall program");module_param_named(cache_getent_timeout, nfs_cache_getent_timeout, ulong, 0600);MODULE_PARM_DESC(cache_getent_timeout, "Timeout (in seconds) after which "		"the cache upcall is assumed to have failed"); int nfs_cache_upcall(struct cache_detail *cd, char *entry_name){	static char *envp[] = { "HOME=/",		"TERM=linux",		"PATH=/sbin:/usr/sbin:/bin:/usr/bin",		NULL	};	char *argv[] = {		nfs_cache_getent_prog,		cd->name,		entry_name,		NULL	};	int ret = -EACCES; 	if (nfs_cache_getent_prog[0] == '\0')		goto out;	ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);	/*	 * Disable the upcall mechanism if we're getting an ENOENT or	 * EACCES error. The admin can re-enable it on the fly by using	 * sysfs to set the 'cache_getent' parameter once the problem	 * has been fixed.	 */	if (ret == -ENOENT || ret == -EACCES)		nfs_cache_getent_prog[0] = '\0';out:	return ret > 0 ? 0 : ret;} /* * Deferred request handling */void nfs_cache_defer_req_put(struct nfs_cache_defer_req *dreq){	if (refcount_dec_and_test(&dreq->count))		kfree(dreq);} static void nfs_dns_cache_revisit(struct cache_deferred_req *d, int toomany){	struct nfs_cache_defer_req *dreq; 	dreq = container_of(d, struct nfs_cache_defer_req, deferred_req); 	complete(&dreq->completion);	nfs_cache_defer_req_put(dreq);} static struct cache_deferred_req *nfs_dns_cache_defer(struct cache_req *req){	struct nfs_cache_defer_req *dreq; 	dreq = container_of(req, struct nfs_cache_defer_req, req);	dreq->deferred_req.revisit = nfs_dns_cache_revisit;	refcount_inc(&dreq->count); 	return &dreq->deferred_req;} struct nfs_cache_defer_req *nfs_cache_defer_req_alloc(void){	struct nfs_cache_defer_req *dreq; 	dreq = kzalloc_obj(*dreq);	if (dreq) {		init_completion(&dreq->completion);		refcount_set(&dreq->count, 1);		dreq->req.defer = nfs_dns_cache_defer;	}	return dreq;} int nfs_cache_wait_for_upcall(struct nfs_cache_defer_req *dreq){	if (wait_for_completion_timeout(&dreq->completion,			nfs_cache_getent_timeout * HZ) == 0)		return -ETIMEDOUT;	return 0;} int nfs_cache_register_sb(struct super_block *sb, struct cache_detail *cd){	int ret;	struct dentry *dir; 	dir = rpc_d_lookup_sb(sb, "cache");	ret = sunrpc_cache_register_pipefs(dir, cd->name, 0600, cd);	dput(dir);	return ret;} int nfs_cache_register_net(struct net *net, struct cache_detail *cd){	struct super_block *pipefs_sb;	int ret = 0; 	sunrpc_init_cache_detail(cd);	pipefs_sb = rpc_get_sb_net(net);	if (pipefs_sb) {		ret = nfs_cache_register_sb(pipefs_sb, cd);		rpc_put_sb_net(net);		if (ret)			sunrpc_destroy_cache_detail(cd);	}	return ret;} void nfs_cache_unregister_sb(struct super_block *sb, struct cache_detail *cd){	sunrpc_cache_unregister_pipefs(cd);} void nfs_cache_unregister_net(struct net *net, struct cache_detail *cd){	struct super_block *pipefs_sb; 	pipefs_sb = rpc_get_sb_net(net);	if (pipefs_sb) {		nfs_cache_unregister_sb(pipefs_sb, cd);		rpc_put_sb_net(net);	}	sunrpc_destroy_cache_detail(cd);}