// 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);
}