cache_lib.c

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/*
 * linux/fs/nfs/cache_lib.c
 *
 * Helper routines for the NFS client caches
 *
 * Copyright (c) 2009 Trond Myklebust <[email protected]>
 */
#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 (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_sb(struct super_block *sb, struct cache_detail *cd)
{
    int ret;
    struct dentry *dir;

    dir = rpc_d_lookup_sb(sb, "cache");
    BUG_ON(dir == NULL);
    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;

    pipefs_sb = rpc_get_sb_net(net);
    if (pipefs_sb) {
        ret = nfs_cache_register_sb(pipefs_sb, cd);
        rpc_put_sb_net(net);
    }
    return ret;
}

void nfs_cache_unregister_sb(struct super_block *sb, struct cache_detail *cd)
{
    if (cd->u.pipefs.dir)
        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);
    }
}

void nfs_cache_init(struct cache_detail *cd)
{
    sunrpc_init_cache_detail(cd);
}

void nfs_cache_destroy(struct cache_detail *cd)
{
    sunrpc_destroy_cache_detail(cd);
}