// SPDX-License-Identifier: GPL-2.0-or-later
/* mountpoint management
 *
 * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/gfp.h>
#include <linux/fs_context.h>
#include "internal.h"


static struct dentry *afs_mntpt_lookup(struct inode *dir,
                                       struct dentry *dentry,
                                       unsigned int flags);
static int afs_mntpt_open(struct inode *inode, struct file *file);
static void afs_mntpt_expiry_timed_out(struct work_struct *work);

const struct file_operations afs_mntpt_file_operations = {
        .open           = afs_mntpt_open,
        .llseek         = noop_llseek,
};

const struct inode_operations afs_mntpt_inode_operations = {
        .lookup         = afs_mntpt_lookup,
        .readlink       = afs_readlink,
        .getattr        = afs_getattr,
};

const struct inode_operations afs_autocell_inode_operations = {
        .getattr        = afs_getattr,
};

static LIST_HEAD(afs_vfsmounts);
static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);

static unsigned long afs_mntpt_expiry_timeout = 10 * 60;

static const char afs_root_volume[] = "root.cell";

/*
 * no valid lookup procedure on this sort of dir
 */
static struct dentry *afs_mntpt_lookup(struct inode *dir,
                                       struct dentry *dentry,
                                       unsigned int flags)
{
        _enter("%p,%p{%pd2}", dir, dentry, dentry);
        return ERR_PTR(-EREMOTE);
}

/*
 * no valid open procedure on this sort of dir
 */
static int afs_mntpt_open(struct inode *inode, struct file *file)
{
        _enter("%p,%p{%pD2}", inode, file, file);
        return -EREMOTE;
}

/*
 * Set the parameters for the proposed superblock.
 */
static int afs_mntpt_set_params(struct fs_context *fc, struct dentry *mntpt)
{
        struct afs_fs_context *ctx = fc->fs_private;
        struct afs_super_info *src_as = AFS_FS_S(mntpt->d_sb);
        struct afs_vnode *vnode = AFS_FS_I(d_inode(mntpt));
        struct afs_cell *cell;
        const char *p;
        int ret;

        if (fc->net_ns != src_as->net_ns) {
                put_net(fc->net_ns);
                fc->net_ns = get_net(src_as->net_ns);
        }

        if (src_as->volume && src_as->volume->type == AFSVL_RWVOL) {
                ctx->type = AFSVL_RWVOL;
                ctx->force = true;
        }
        if (ctx->cell) {
                afs_unuse_cell(ctx->cell, afs_cell_trace_unuse_mntpt);
                ctx->cell = NULL;
        }
        if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
                /* if the directory is a pseudo directory, use the d_name */
                unsigned size = mntpt->d_name.len;

                if (size < 2)
                        return -ENOENT;

                p = mntpt->d_name.name;
                if (mntpt->d_name.name[0] == '.') {
                        size--;
                        p++;
                        ctx->type = AFSVL_RWVOL;
                        ctx->force = true;
                }
                if (size > AFS_MAXCELLNAME)
                        return -ENAMETOOLONG;

                cell = afs_lookup_cell(ctx->net, p, size, NULL,
                                       AFS_LOOKUP_CELL_MOUNTPOINT,
                                       afs_cell_trace_use_lookup_mntpt);
                if (IS_ERR(cell)) {
                        pr_err("kAFS: unable to lookup cell '%pd'\n", mntpt);
                        return PTR_ERR(cell);
                }
                ctx->cell = cell;

                ctx->volname = afs_root_volume;
                ctx->volnamesz = sizeof(afs_root_volume) - 1;
        } else {
                /* read the contents of the AFS special symlink */
                DEFINE_DELAYED_CALL(cleanup);
                const char *content;
                loff_t size = i_size_read(d_inode(mntpt));

                if (src_as->cell)
                        ctx->cell = afs_use_cell(src_as->cell, afs_cell_trace_use_mntpt);

                if (size < 2 || size > PAGE_SIZE - 1)
                        return -EINVAL;

                content = afs_get_link(mntpt, d_inode(mntpt), &cleanup);
                if (IS_ERR(content)) {
                        do_delayed_call(&cleanup);
                        return PTR_ERR(content);
                }

                ret = -EINVAL;
                if (content[size - 1] == '.')
                        ret = vfs_parse_fs_qstr(fc, "source",
                                                &QSTR_LEN(content, size - 1));
                do_delayed_call(&cleanup);
                if (ret < 0)
                        return ret;

                /* Don't cross a backup volume mountpoint from a backup volume */
                if (src_as->volume && src_as->volume->type == AFSVL_BACKVOL &&
                    ctx->type == AFSVL_BACKVOL)
                        return -ENODEV;
        }

        return 0;
}

/*
 * create a vfsmount to be automounted
 */
static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
{
        struct fs_context *fc;
        struct vfsmount *mnt;
        int ret;

        BUG_ON(!d_inode(mntpt));

        fc = fs_context_for_submount(&afs_fs_type, mntpt);
        if (IS_ERR(fc))
                return ERR_CAST(fc);

        ret = afs_mntpt_set_params(fc, mntpt);
        if (!ret)
                mnt = fc_mount(fc);
        else
                mnt = ERR_PTR(ret);

        put_fs_context(fc);
        return mnt;
}

/*
 * handle an automount point
 */
struct vfsmount *afs_d_automount(struct path *path)
{
        struct vfsmount *newmnt;

        _enter("{%pd}", path->dentry);

        newmnt = afs_mntpt_do_automount(path->dentry);
        if (IS_ERR(newmnt))
                return newmnt;

        mnt_set_expiry(newmnt, &afs_vfsmounts);
        queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
                           afs_mntpt_expiry_timeout * HZ);
        _leave(" = %p", newmnt);
        return newmnt;
}

/*
 * handle mountpoint expiry timer going off
 */
static void afs_mntpt_expiry_timed_out(struct work_struct *work)
{
        _enter("");

        if (!list_empty(&afs_vfsmounts)) {
                mark_mounts_for_expiry(&afs_vfsmounts);
                queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
                                   afs_mntpt_expiry_timeout * HZ);
        }

        _leave("");
}

/*
 * kill the AFS mountpoint timer if it's still running
 */
void afs_mntpt_kill_timer(void)
{
        _enter("");

        ASSERT(list_empty(&afs_vfsmounts));
        cancel_delayed_work_sync(&afs_mntpt_expiry_timer);
}