/* * 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/sunrpc/cache.h> #include <linux/sunrpc/rpc_pipe_fs.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 (atomic_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_all(&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; atomic_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(sizeof(*dreq), GFP_KERNEL); if (dreq) { init_completion(&dreq->completion); atomic_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(struct cache_detail *cd) { struct nameidata nd; struct vfsmount *mnt; int ret; mnt = rpc_get_mount(); if (IS_ERR(mnt)) return PTR_ERR(mnt); ret = vfs_path_lookup(mnt->mnt_root, mnt, "/cache", 0, &nd); if (ret) goto err; ret = sunrpc_cache_register_pipefs(nd.path.dentry, cd->name, 0600, cd); path_put(&nd.path); if (!ret) return ret; err: rpc_put_mount(); return ret; } void nfs_cache_unregister(struct cache_detail *cd) { sunrpc_cache_unregister_pipefs(cd); rpc_put_mount(); }