nfs4super.c

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/*
 * Copyright (c) 2012 Bryan Schumaker <[email protected]>
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/nfs_idmap.h>
#include <linux/nfs4_mount.h>
#include <linux/nfs_fs.h>
#include "delegation.h"
#include "internal.h"
#include "nfs4_fs.h"
#include "pnfs.h"
#include "nfs.h"

#define NFSDBG_FACILITY     NFSDBG_VFS

static int nfs4_write_inode(struct inode *inode, struct writeback_control *wbc);
static void nfs4_evict_inode(struct inode *inode);
static struct dentry *nfs4_remote_mount(struct file_system_type *fs_type,
    int flags, const char *dev_name, void *raw_data);
static struct dentry *nfs4_referral_mount(struct file_system_type *fs_type,
    int flags, const char *dev_name, void *raw_data);
static struct dentry *nfs4_remote_referral_mount(struct file_system_type *fs_type,
    int flags, const char *dev_name, void *raw_data);

static struct file_system_type nfs4_remote_fs_type = {
    .owner      = THIS_MODULE,
    .name       = "nfs4",
    .mount      = nfs4_remote_mount,
    .kill_sb    = nfs_kill_super,
    .fs_flags   = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
};

static struct file_system_type nfs4_remote_referral_fs_type = {
    .owner      = THIS_MODULE,
    .name       = "nfs4",
    .mount      = nfs4_remote_referral_mount,
    .kill_sb    = nfs_kill_super,
    .fs_flags   = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
};

struct file_system_type nfs4_referral_fs_type = {
    .owner      = THIS_MODULE,
    .name       = "nfs4",
    .mount      = nfs4_referral_mount,
    .kill_sb    = nfs_kill_super,
    .fs_flags   = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
};

static const struct super_operations nfs4_sops = {
    .alloc_inode    = nfs_alloc_inode,
    .destroy_inode  = nfs_destroy_inode,
    .write_inode    = nfs4_write_inode,
    .put_super  = nfs_put_super,
    .statfs     = nfs_statfs,
    .evict_inode    = nfs4_evict_inode,
    .umount_begin   = nfs_umount_begin,
    .show_options   = nfs_show_options,
    .show_devname   = nfs_show_devname,
    .show_path  = nfs_show_path,
    .show_stats = nfs_show_stats,
    .remount_fs = nfs_remount,
};

struct nfs_subversion nfs_v4 = {
    .owner = THIS_MODULE,
    .nfs_fs   = &nfs4_fs_type,
    .rpc_vers = &nfs_version4,
    .rpc_ops  = &nfs_v4_clientops,
    .sops     = &nfs4_sops,
    .xattr    = nfs4_xattr_handlers,
};

static int nfs4_write_inode(struct inode *inode, struct writeback_control *wbc)
{
    int ret = nfs_write_inode(inode, wbc);

    if (ret >= 0 && test_bit(NFS_INO_LAYOUTCOMMIT, &NFS_I(inode)->flags)) {
        int status;
        bool sync = true;

        if (wbc->sync_mode == WB_SYNC_NONE)
            sync = false;

        status = pnfs_layoutcommit_inode(inode, sync);
        if (status < 0)
            return status;
    }
    return ret;
}

/*
 * Clean out any remaining NFSv4 state that might be left over due
 * to open() calls that passed nfs_atomic_lookup, but failed to call
 * nfs_open().
 */
static void nfs4_evict_inode(struct inode *inode)
{
    truncate_inode_pages(&inode->i_data, 0);
    clear_inode(inode);
    pnfs_return_layout(inode);
    pnfs_destroy_layout(NFS_I(inode));
    /* If we are holding a delegation, return it! */
    nfs_inode_return_delegation_noreclaim(inode);
    /* First call standard NFS clear_inode() code */
    nfs_clear_inode(inode);
}

/*
 * Get the superblock for the NFS4 root partition
 */
static struct dentry *
nfs4_remote_mount(struct file_system_type *fs_type, int flags,
          const char *dev_name, void *info)
{
    struct nfs_mount_info *mount_info = info;
    struct nfs_server *server;
    struct dentry *mntroot = ERR_PTR(-ENOMEM);

    mount_info->set_security = nfs_set_sb_security;

    /* Get a volume representation */
    server = nfs4_create_server(mount_info, &nfs_v4);
    if (IS_ERR(server)) {
        mntroot = ERR_CAST(server);
        goto out;
    }

    mntroot = nfs_fs_mount_common(server, flags, dev_name, mount_info, &nfs_v4);

out:
    return mntroot;
}

static struct vfsmount *nfs_do_root_mount(struct file_system_type *fs_type,
        int flags, void *data, const char *hostname)
{
    struct vfsmount *root_mnt;
    char *root_devname;
    size_t len;

    len = strlen(hostname) + 5;
    root_devname = kmalloc(len, GFP_KERNEL);
    if (root_devname == NULL)
        return ERR_PTR(-ENOMEM);
    /* Does hostname needs to be enclosed in brackets? */
    if (strchr(hostname, ':'))
        snprintf(root_devname, len, "[%s]:/", hostname);
    else
        snprintf(root_devname, len, "%s:/", hostname);
    root_mnt = vfs_kern_mount(fs_type, flags, root_devname, data);
    kfree(root_devname);
    return root_mnt;
}

struct nfs_referral_count {
    struct list_head list;
    const struct task_struct *task;
    unsigned int referral_count;
};

static LIST_HEAD(nfs_referral_count_list);
static DEFINE_SPINLOCK(nfs_referral_count_list_lock);

static struct nfs_referral_count *nfs_find_referral_count(void)
{
    struct nfs_referral_count *p;

    list_for_each_entry(p, &nfs_referral_count_list, list) {
        if (p->task == current)
            return p;
    }
    return NULL;
}

#define NFS_MAX_NESTED_REFERRALS 2

static int nfs_referral_loop_protect(void)
{
    struct nfs_referral_count *p, *new;
    int ret = -ENOMEM;

    new = kmalloc(sizeof(*new), GFP_KERNEL);
    if (!new)
        goto out;
    new->task = current;
    new->referral_count = 1;

    ret = 0;
    spin_lock(&nfs_referral_count_list_lock);
    p = nfs_find_referral_count();
    if (p != NULL) {
        if (p->referral_count >= NFS_MAX_NESTED_REFERRALS)
            ret = -ELOOP;
        else
            p->referral_count++;
    } else {
        list_add(&new->list, &nfs_referral_count_list);
        new = NULL;
    }
    spin_unlock(&nfs_referral_count_list_lock);
    kfree(new);
out:
    return ret;
}

static void nfs_referral_loop_unprotect(void)
{
    struct nfs_referral_count *p;

    spin_lock(&nfs_referral_count_list_lock);
    p = nfs_find_referral_count();
    p->referral_count--;
    if (p->referral_count == 0)
        list_del(&p->list);
    else
        p = NULL;
    spin_unlock(&nfs_referral_count_list_lock);
    kfree(p);
}

static struct dentry *nfs_follow_remote_path(struct vfsmount *root_mnt,
        const char *export_path)
{
    struct dentry *dentry;
    int err;

    if (IS_ERR(root_mnt))
        return ERR_CAST(root_mnt);

    err = nfs_referral_loop_protect();
    if (err) {
        mntput(root_mnt);
        return ERR_PTR(err);
    }

    dentry = mount_subtree(root_mnt, export_path);
    nfs_referral_loop_unprotect();

    return dentry;
}

struct dentry *nfs4_try_mount(int flags, const char *dev_name,
                  struct nfs_mount_info *mount_info,
                  struct nfs_subversion *nfs_mod)
{
    char *export_path;
    struct vfsmount *root_mnt;
    struct dentry *res;
    struct nfs_parsed_mount_data *data = mount_info->parsed;

    dfprintk(MOUNT, "--> nfs4_try_mount()\n");

    export_path = data->nfs_server.export_path;
    data->nfs_server.export_path = "/";
    root_mnt = nfs_do_root_mount(&nfs4_remote_fs_type, flags, mount_info,
            data->nfs_server.hostname);
    data->nfs_server.export_path = export_path;

    res = nfs_follow_remote_path(root_mnt, export_path);

    dfprintk(MOUNT, "<-- nfs4_try_mount() = %ld%s\n",
            IS_ERR(res) ? PTR_ERR(res) : 0,
            IS_ERR(res) ? " [error]" : "");
    return res;
}

static struct dentry *
nfs4_remote_referral_mount(struct file_system_type *fs_type, int flags,
               const char *dev_name, void *raw_data)
{
    struct nfs_mount_info mount_info = {
        .fill_super = nfs_fill_super,
        .set_security = nfs_clone_sb_security,
        .cloned = raw_data,
    };
    struct nfs_server *server;
    struct dentry *mntroot = ERR_PTR(-ENOMEM);

    dprintk("--> nfs4_referral_get_sb()\n");

    mount_info.mntfh = nfs_alloc_fhandle();
    if (mount_info.cloned == NULL || mount_info.mntfh == NULL)
        goto out;

    /* create a new volume representation */
    server = nfs4_create_referral_server(mount_info.cloned, mount_info.mntfh);
    if (IS_ERR(server)) {
        mntroot = ERR_CAST(server);
        goto out;
    }

    mntroot = nfs_fs_mount_common(server, flags, dev_name, &mount_info, &nfs_v4);
out:
    nfs_free_fhandle(mount_info.mntfh);
    return mntroot;
}

/*
 * Create an NFS4 server record on referral traversal
 */
static struct dentry *nfs4_referral_mount(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *raw_data)
{
    struct nfs_clone_mount *data = raw_data;
    char *export_path;
    struct vfsmount *root_mnt;
    struct dentry *res;

    dprintk("--> nfs4_referral_mount()\n");

    export_path = data->mnt_path;
    data->mnt_path = "/";

    root_mnt = nfs_do_root_mount(&nfs4_remote_referral_fs_type,
            flags, data, data->hostname);
    data->mnt_path = export_path;

    res = nfs_follow_remote_path(root_mnt, export_path);
    dprintk("<-- nfs4_referral_mount() = %ld%s\n",
            IS_ERR(res) ? PTR_ERR(res) : 0,
            IS_ERR(res) ? " [error]" : "");
    return res;
}


static int __init init_nfs_v4(void)
{
    int err;

    err = nfs_idmap_init();
    if (err)
        goto out;

    err = nfs4_register_sysctl();
    if (err)
        goto out1;

    register_nfs_version(&nfs_v4);
    return 0;
out1:
    nfs_idmap_quit();
out:
    return err;
}

static void __exit exit_nfs_v4(void)
{
    unregister_nfs_version(&nfs_v4);
    nfs4_unregister_sysctl();
    nfs_idmap_quit();
}

MODULE_LICENSE("GPL");

module_init(init_nfs_v4);
module_exit(exit_nfs_v4);