// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2012 Bryan Schumaker <bjschuma@netapp.com>
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/nfs4_mount.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_ssc.h>
#include "delegation.h"
#include "internal.h"
#include "nfs4_fs.h"
#include "nfs4idmap.h"
#include "dns_resolve.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 const struct super_operations nfs4_sops = {
        .alloc_inode    = nfs_alloc_inode,
        .free_inode     = nfs_free_inode,
        .write_inode    = nfs4_write_inode,
        .drop_inode     = nfs_drop_inode,
        .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,
};

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)
                ret = pnfs_layoutcommit_inode(inode,
                                wbc->sync_mode == WB_SYNC_ALL);
        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_final(&inode->i_data);
        clear_inode(inode);
        /* If we are holding a delegation, return and free it */
        nfs_inode_evict_delegation(inode);
        /* Note that above delegreturn would trigger pnfs return-on-close */
        pnfs_return_layout(inode);
        pnfs_destroy_layout_final(NFS_I(inode));
        /* First call standard NFS clear_inode() code */
        nfs_clear_inode(inode);
        nfs4_xattr_cache_zap(inode);
}

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_obj(*new);
        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 int do_nfs4_mount(struct nfs_server *server,
                         struct fs_context *fc,
                         const char *hostname,
                         const char *export_path)
{
        struct nfs_fs_context *root_ctx;
        struct nfs_fs_context *ctx;
        struct fs_context *root_fc;
        struct vfsmount *root_mnt;
        struct dentry *dentry;
        char *source;
        int ret;

        if (IS_ERR(server))
                return PTR_ERR(server);

        root_fc = vfs_dup_fs_context(fc);
        if (IS_ERR(root_fc)) {
                nfs_free_server(server);
                return PTR_ERR(root_fc);
        }
        kfree(root_fc->source);
        root_fc->source = NULL;

        ctx = nfs_fc2context(fc);
        root_ctx = nfs_fc2context(root_fc);
        root_ctx->internal = true;
        root_ctx->server = server;

        if (ctx->fscache_uniq) {
                ret = vfs_parse_fs_string(root_fc, "fsc", ctx->fscache_uniq);
                if (ret < 0) {
                        put_fs_context(root_fc);
                        return ret;
                }
        }
        /* We leave export_path unset as it's not used to find the root. */

        /* Does hostname needs to be enclosed in brackets? */
        if (strchr(hostname, ':'))
                source = kasprintf(GFP_KERNEL, "[%s]:/", hostname);
        else
                source = kasprintf(GFP_KERNEL, "%s:/", hostname);

        if (!source) {
                put_fs_context(root_fc);
                return -ENOMEM;
        }
        ret = vfs_parse_fs_string(root_fc, "source", source);
        kfree(source);
        if (ret < 0) {
                put_fs_context(root_fc);
                return ret;
        }
        root_mnt = fc_mount(root_fc);
        put_fs_context(root_fc);

        if (IS_ERR(root_mnt))
                return PTR_ERR(root_mnt);

        ret = nfs_referral_loop_protect();
        if (ret) {
                mntput(root_mnt);
                return ret;
        }

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

        if (IS_ERR(dentry))
                return PTR_ERR(dentry);

        fc->root = dentry;
        return 0;
}

int nfs4_try_get_tree(struct fs_context *fc)
{
        struct nfs_fs_context *ctx = nfs_fc2context(fc);
        int err;

        dfprintk(MOUNT, "--> nfs4_try_get_tree()\n");

        /* We create a mount for the server's root, walk to the requested
         * location and then create another mount for that.
         */
        err= do_nfs4_mount(nfs4_create_server(fc),
                           fc, ctx->nfs_server.hostname,
                           ctx->nfs_server.export_path);
        if (err) {
                nfs_ferrorf(fc, MOUNT, "NFS4: Couldn't follow remote path");
                dfprintk(MOUNT, "<-- nfs4_try_get_tree() = %d [error]\n", err);
        } else {
                dfprintk(MOUNT, "<-- nfs4_try_get_tree() = 0\n");
        }
        return err;
}

/*
 * Create an NFS4 server record on referral traversal
 */
int nfs4_get_referral_tree(struct fs_context *fc)
{
        struct nfs_fs_context *ctx = nfs_fc2context(fc);
        int err;

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

        /* create a new volume representation */
        err = do_nfs4_mount(nfs4_create_referral_server(fc),
                            fc, ctx->nfs_server.hostname,
                            ctx->nfs_server.export_path);
        if (err) {
                nfs_ferrorf(fc, MOUNT, "NFS4: Couldn't follow remote path");
                dfprintk(MOUNT, "<-- nfs4_get_referral_tree() = %d [error]\n", err);
        } else {
                dfprintk(MOUNT, "<-- nfs4_get_referral_tree() = 0\n");
        }
        return err;
}

static int __init init_nfs_v4(void)
{
        int err;

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

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

#ifdef CONFIG_NFS_V4_2
        err = nfs4_xattr_cache_init();
        if (err)
                goto out2;
#endif

        err = nfs4_register_sysctl();
        if (err)
                goto out2;

#ifdef CONFIG_NFS_V4_2
        nfs42_ssc_register_ops();
#endif
        register_nfs_version(&nfs_v4);
        return 0;
out2:
        nfs_idmap_quit();
out1:
        nfs_dns_resolver_destroy();
out:
        return err;
}

static void __exit exit_nfs_v4(void)
{
        /* Not called in the _init(), conditionally loaded */
        nfs4_pnfs_v3_ds_connect_unload();

        unregister_nfs_version(&nfs_v4);
#ifdef CONFIG_NFS_V4_2
        nfs4_xattr_cache_exit();
        nfs42_ssc_unregister_ops();
#endif
        nfs4_unregister_sysctl();
        nfs_idmap_quit();
        nfs_dns_resolver_destroy();
}

MODULE_DESCRIPTION("NFSv4 client support");
MODULE_LICENSE("GPL");

module_init(init_nfs_v4);
module_exit(exit_nfs_v4);