// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * dlmfs.c
 *
 * Code which implements the kernel side of a minimal userspace
 * interface to our DLM. This file handles the virtual file system
 * used for communication with userspace. Credit should go to ramfs,
 * which was a template for the fs side of this module.
 *
 * Copyright (C) 2003, 2004 Oracle.  All rights reserved.
 */

/* Simple VFS hooks based on: */
/*
 * Resizable simple ram filesystem for Linux.
 *
 * Copyright (C) 2000 Linus Torvalds.
 *               2000 Transmeta Corp.
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/fs_context.h>
#include <linux/pagemap.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/backing-dev.h>
#include <linux/poll.h>

#include <linux/uaccess.h>

#include "../stackglue.h"
#include "userdlm.h"

#define MLOG_MASK_PREFIX ML_DLMFS
#include "../cluster/masklog.h"


static const struct super_operations dlmfs_ops;
static const struct file_operations dlmfs_file_operations;
static const struct inode_operations dlmfs_dir_inode_operations;
static const struct inode_operations dlmfs_root_inode_operations;
static const struct inode_operations dlmfs_file_inode_operations;
static struct kmem_cache *dlmfs_inode_cache;

struct workqueue_struct *user_dlm_worker;



/*
 * These are the ABI capabilities of dlmfs.
 *
 * Over time, dlmfs has added some features that were not part of the
 * initial ABI.  Unfortunately, some of these features are not detectable
 * via standard usage.  For example, Linux's default poll always returns
 * EPOLLIN, so there is no way for a caller of poll(2) to know when dlmfs
 * added poll support.  Instead, we provide this list of new capabilities.
 *
 * Capabilities is a read-only attribute.  We do it as a module parameter
 * so we can discover it whether dlmfs is built in, loaded, or even not
 * loaded.
 *
 * The ABI features are local to this machine's dlmfs mount.  This is
 * distinct from the locking protocol, which is concerned with inter-node
 * interaction.
 *
 * Capabilities:
 * - bast       : EPOLLIN against the file descriptor of a held lock
 *                signifies a bast fired on the lock.
 */
#define DLMFS_CAPABILITIES "bast stackglue"
static int param_set_dlmfs_capabilities(const char *val,
                                        const struct kernel_param *kp)
{
        printk(KERN_ERR "%s: readonly parameter\n", kp->name);
        return -EINVAL;
}
static int param_get_dlmfs_capabilities(char *buffer,
                                        const struct kernel_param *kp)
{
        return sysfs_emit(buffer, DLMFS_CAPABILITIES);
}
module_param_call(capabilities, param_set_dlmfs_capabilities,
                  param_get_dlmfs_capabilities, NULL, 0444);
MODULE_PARM_DESC(capabilities, DLMFS_CAPABILITIES);


/*
 * decodes a set of open flags into a valid lock level and a set of flags.
 * returns < 0 if we have invalid flags
 * flags which mean something to us:
 * O_RDONLY -> PRMODE level
 * O_WRONLY -> EXMODE level
 *
 * O_NONBLOCK -> NOQUEUE
 */
static int dlmfs_decode_open_flags(int open_flags,
                                   int *level,
                                   int *flags)
{
        if (open_flags & (O_WRONLY|O_RDWR))
                *level = DLM_LOCK_EX;
        else
                *level = DLM_LOCK_PR;

        *flags = 0;
        if (open_flags & O_NONBLOCK)
                *flags |= DLM_LKF_NOQUEUE;

        return 0;
}

static int dlmfs_file_open(struct inode *inode,
                           struct file *file)
{
        int status, level, flags;
        struct dlmfs_filp_private *fp = NULL;
        struct dlmfs_inode_private *ip;

        if (S_ISDIR(inode->i_mode))
                BUG();

        mlog(0, "open called on inode %lu, flags 0x%x\n", inode->i_ino,
                file->f_flags);

        status = dlmfs_decode_open_flags(file->f_flags, &level, &flags);
        if (status < 0)
                goto bail;

        /* We don't want to honor O_APPEND at read/write time as it
         * doesn't make sense for LVB writes. */
        file->f_flags &= ~O_APPEND;

        fp = kmalloc_obj(*fp, GFP_NOFS);
        if (!fp) {
                status = -ENOMEM;
                goto bail;
        }
        fp->fp_lock_level = level;

        ip = DLMFS_I(inode);

        status = user_dlm_cluster_lock(&ip->ip_lockres, level, flags);
        if (status < 0) {
                /* this is a strange error to return here but I want
                 * to be able userspace to be able to distinguish a
                 * valid lock request from one that simply couldn't be
                 * granted. */
                if (flags & DLM_LKF_NOQUEUE && status == -EAGAIN)
                        status = -ETXTBSY;
                kfree(fp);
                goto bail;
        }

        file->private_data = fp;
bail:
        return status;
}

static int dlmfs_file_release(struct inode *inode,
                              struct file *file)
{
        int level;
        struct dlmfs_inode_private *ip = DLMFS_I(inode);
        struct dlmfs_filp_private *fp = file->private_data;

        if (S_ISDIR(inode->i_mode))
                BUG();

        mlog(0, "close called on inode %lu\n", inode->i_ino);

        if (fp) {
                level = fp->fp_lock_level;
                if (level != DLM_LOCK_IV)
                        user_dlm_cluster_unlock(&ip->ip_lockres, level);

                kfree(fp);
                file->private_data = NULL;
        }

        return 0;
}

/*
 * We do ->setattr() just to override size changes.  Our size is the size
 * of the LVB and nothing else.
 */
static int dlmfs_file_setattr(struct mnt_idmap *idmap,
                              struct dentry *dentry, struct iattr *attr)
{
        int error;
        struct inode *inode = d_inode(dentry);

        attr->ia_valid &= ~ATTR_SIZE;
        error = setattr_prepare(&nop_mnt_idmap, dentry, attr);
        if (error)
                return error;

        setattr_copy(&nop_mnt_idmap, inode, attr);
        mark_inode_dirty(inode);
        return 0;
}

static __poll_t dlmfs_file_poll(struct file *file, poll_table *wait)
{
        __poll_t event = 0;
        struct inode *inode = file_inode(file);
        struct dlmfs_inode_private *ip = DLMFS_I(inode);

        poll_wait(file, &ip->ip_lockres.l_event, wait);

        spin_lock(&ip->ip_lockres.l_lock);
        if (ip->ip_lockres.l_flags & USER_LOCK_BLOCKED)
                event = EPOLLIN | EPOLLRDNORM;
        spin_unlock(&ip->ip_lockres.l_lock);

        return event;
}

static ssize_t dlmfs_file_read(struct file *file,
                               char __user *buf,
                               size_t count,
                               loff_t *ppos)
{
        char lvb[DLM_LVB_LEN];

        if (!user_dlm_read_lvb(file_inode(file), lvb))
                return 0;

        return simple_read_from_buffer(buf, count, ppos, lvb, sizeof(lvb));
}

static ssize_t dlmfs_file_write(struct file *filp,
                                const char __user *buf,
                                size_t count,
                                loff_t *ppos)
{
        char lvb_buf[DLM_LVB_LEN];
        int bytes_left;
        struct inode *inode = file_inode(filp);

        mlog(0, "inode %lu, count = %zu, *ppos = %llu\n",
                inode->i_ino, count, *ppos);

        if (*ppos >= DLM_LVB_LEN)
                return -ENOSPC;

        /* don't write past the lvb */
        if (count > DLM_LVB_LEN - *ppos)
                count = DLM_LVB_LEN - *ppos;

        if (!count)
                return 0;

        bytes_left = copy_from_user(lvb_buf, buf, count);
        count -= bytes_left;
        if (count)
                user_dlm_write_lvb(inode, lvb_buf, count);

        *ppos = *ppos + count;
        mlog(0, "wrote %zu bytes\n", count);
        return count;
}

static void dlmfs_init_once(void *foo)
{
        struct dlmfs_inode_private *ip =
                (struct dlmfs_inode_private *) foo;

        ip->ip_conn = NULL;
        ip->ip_parent = NULL;

        inode_init_once(&ip->ip_vfs_inode);
}

static struct inode *dlmfs_alloc_inode(struct super_block *sb)
{
        struct dlmfs_inode_private *ip;

        ip = alloc_inode_sb(sb, dlmfs_inode_cache, GFP_NOFS);
        if (!ip)
                return NULL;

        return &ip->ip_vfs_inode;
}

static void dlmfs_free_inode(struct inode *inode)
{
        kmem_cache_free(dlmfs_inode_cache, DLMFS_I(inode));
}

static void dlmfs_evict_inode(struct inode *inode)
{
        int status;
        struct dlmfs_inode_private *ip;
        struct user_lock_res *lockres;
        int teardown;

        clear_inode(inode);

        mlog(0, "inode %lu\n", inode->i_ino);

        ip = DLMFS_I(inode);
        lockres = &ip->ip_lockres;

        if (S_ISREG(inode->i_mode)) {
                spin_lock(&lockres->l_lock);
                teardown = !!(lockres->l_flags & USER_LOCK_IN_TEARDOWN);
                spin_unlock(&lockres->l_lock);
                if (!teardown) {
                        status = user_dlm_destroy_lock(lockres);
                        if (status < 0)
                                mlog_errno(status);
                }
                iput(ip->ip_parent);
                goto clear_fields;
        }

        mlog(0, "we're a directory, ip->ip_conn = 0x%p\n", ip->ip_conn);
        /* we must be a directory. If required, lets unregister the
         * dlm context now. */
        if (ip->ip_conn)
                user_dlm_unregister(ip->ip_conn);
clear_fields:
        ip->ip_parent = NULL;
        ip->ip_conn = NULL;
}

static struct inode *dlmfs_get_root_inode(struct super_block *sb)
{
        struct inode *inode = new_inode(sb);
        umode_t mode = S_IFDIR | 0755;

        if (inode) {
                inode->i_ino = get_next_ino();
                inode_init_owner(&nop_mnt_idmap, inode, NULL, mode);
                simple_inode_init_ts(inode);
                inc_nlink(inode);

                inode->i_fop = &simple_dir_operations;
                inode->i_op = &dlmfs_root_inode_operations;
        }

        return inode;
}

static struct inode *dlmfs_get_inode(struct inode *parent,
                                     struct dentry *dentry,
                                     umode_t mode)
{
        struct super_block *sb = parent->i_sb;
        struct inode * inode = new_inode(sb);
        struct dlmfs_inode_private *ip;

        if (!inode)
                return NULL;

        inode->i_ino = get_next_ino();
        inode_init_owner(&nop_mnt_idmap, inode, parent, mode);
        simple_inode_init_ts(inode);

        ip = DLMFS_I(inode);
        ip->ip_conn = DLMFS_I(parent)->ip_conn;

        switch (mode & S_IFMT) {
        default:
                /* for now we don't support anything other than
                 * directories and regular files. */
                BUG();
                break;
        case S_IFREG:
                inode->i_op = &dlmfs_file_inode_operations;
                inode->i_fop = &dlmfs_file_operations;

                i_size_write(inode,  DLM_LVB_LEN);

                user_dlm_lock_res_init(&ip->ip_lockres, dentry);

                /* released at clear_inode time, this insures that we
                 * get to drop the dlm reference on each lock *before*
                 * we call the unregister code for releasing parent
                 * directories. */
                ip->ip_parent = igrab(parent);
                BUG_ON(!ip->ip_parent);
                break;
        case S_IFDIR:
                inode->i_op = &dlmfs_dir_inode_operations;
                inode->i_fop = &simple_dir_operations;

                /* directory inodes start off with i_nlink ==
                 * 2 (for "." entry) */
                inc_nlink(inode);
                break;
        }
        return inode;
}

/*
 * File creation. Allocate an inode, and we're done..
 */
/* SMP-safe */
static struct dentry *dlmfs_mkdir(struct mnt_idmap * idmap,
                                  struct inode * dir,
                                  struct dentry * dentry,
                                  umode_t mode)
{
        int status;
        struct inode *inode = NULL;
        const struct qstr *domain = &dentry->d_name;
        struct dlmfs_inode_private *ip;
        struct ocfs2_cluster_connection *conn;

        mlog(0, "mkdir %.*s\n", domain->len, domain->name);

        /* verify that we have a proper domain */
        if (domain->len >= GROUP_NAME_MAX) {
                status = -EINVAL;
                mlog(ML_ERROR, "invalid domain name for directory.\n");
                goto bail;
        }

        inode = dlmfs_get_inode(dir, dentry, mode | S_IFDIR);
        if (!inode) {
                status = -ENOMEM;
                mlog_errno(status);
                goto bail;
        }

        ip = DLMFS_I(inode);

        conn = user_dlm_register(domain);
        if (IS_ERR(conn)) {
                status = PTR_ERR(conn);
                mlog(ML_ERROR, "Error %d could not register domain \"%.*s\"\n",
                     status, domain->len, domain->name);
                goto bail;
        }
        ip->ip_conn = conn;

        inc_nlink(dir);
        d_make_persistent(dentry, inode);

        status = 0;
bail:
        if (status < 0)
                iput(inode);
        return ERR_PTR(status);
}

static int dlmfs_create(struct mnt_idmap *idmap,
                        struct inode *dir,
                        struct dentry *dentry,
                        umode_t mode,
                        bool excl)
{
        int status = 0;
        struct inode *inode;
        const struct qstr *name = &dentry->d_name;

        mlog(0, "create %.*s\n", name->len, name->name);

        /* verify name is valid and doesn't contain any dlm reserved
         * characters */
        if (name->len >= USER_DLM_LOCK_ID_MAX_LEN ||
            name->name[0] == '$') {
                status = -EINVAL;
                mlog(ML_ERROR, "invalid lock name, %.*s\n", name->len,
                     name->name);
                goto bail;
        }

        inode = dlmfs_get_inode(dir, dentry, mode | S_IFREG);
        if (!inode) {
                status = -ENOMEM;
                mlog_errno(status);
                goto bail;
        }

        d_make_persistent(dentry, inode);
bail:
        return status;
}

static int dlmfs_unlink(struct inode *dir,
                        struct dentry *dentry)
{
        int status;
        struct inode *inode = d_inode(dentry);

        mlog(0, "unlink inode %lu\n", inode->i_ino);

        /* if there are no current holders, or none that are waiting
         * to acquire a lock, this basically destroys our lockres. */
        status = user_dlm_destroy_lock(&DLMFS_I(inode)->ip_lockres);
        if (status < 0) {
                mlog(ML_ERROR, "unlink %pd, error %d from destroy\n",
                     dentry, status);
                goto bail;
        }
        status = simple_unlink(dir, dentry);
bail:
        return status;
}

static int dlmfs_fill_super(struct super_block *sb, struct fs_context *fc)
{
        sb->s_maxbytes = MAX_LFS_FILESIZE;
        sb->s_blocksize = PAGE_SIZE;
        sb->s_blocksize_bits = PAGE_SHIFT;
        sb->s_magic = DLMFS_MAGIC;
        sb->s_op = &dlmfs_ops;
        sb->s_root = d_make_root(dlmfs_get_root_inode(sb));
        if (!sb->s_root)
                return -ENOMEM;
        return 0;
}

static const struct file_operations dlmfs_file_operations = {
        .open           = dlmfs_file_open,
        .release        = dlmfs_file_release,
        .poll           = dlmfs_file_poll,
        .read           = dlmfs_file_read,
        .write          = dlmfs_file_write,
        .llseek         = default_llseek,
};

static const struct inode_operations dlmfs_dir_inode_operations = {
        .create         = dlmfs_create,
        .lookup         = simple_lookup,
        .unlink         = dlmfs_unlink,
};

/* this way we can restrict mkdir to only the toplevel of the fs. */
static const struct inode_operations dlmfs_root_inode_operations = {
        .lookup         = simple_lookup,
        .mkdir          = dlmfs_mkdir,
        .rmdir          = simple_rmdir,
};

static const struct super_operations dlmfs_ops = {
        .statfs         = simple_statfs,
        .alloc_inode    = dlmfs_alloc_inode,
        .free_inode     = dlmfs_free_inode,
        .evict_inode    = dlmfs_evict_inode,
        .drop_inode     = inode_just_drop,
};

static const struct inode_operations dlmfs_file_inode_operations = {
        .getattr        = simple_getattr,
        .setattr        = dlmfs_file_setattr,
};

static int dlmfs_get_tree(struct fs_context *fc)
{
        return get_tree_nodev(fc, dlmfs_fill_super);
}

static const struct fs_context_operations dlmfs_context_ops = {
        .get_tree       = dlmfs_get_tree,
};

static int dlmfs_init_fs_context(struct fs_context *fc)
{
        fc->ops = &dlmfs_context_ops;

        return 0;
}

static struct file_system_type dlmfs_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "ocfs2_dlmfs",
        .kill_sb        = kill_anon_super,
        .init_fs_context = dlmfs_init_fs_context,
};
MODULE_ALIAS_FS("ocfs2_dlmfs");

static int __init init_dlmfs_fs(void)
{
        int status;
        int cleanup_inode = 0, cleanup_worker = 0;

        dlmfs_inode_cache = kmem_cache_create("dlmfs_inode_cache",
                                sizeof(struct dlmfs_inode_private),
                                0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
                                        SLAB_ACCOUNT),
                                dlmfs_init_once);
        if (!dlmfs_inode_cache) {
                status = -ENOMEM;
                goto bail;
        }
        cleanup_inode = 1;

        user_dlm_worker = alloc_workqueue("user_dlm",
                                          WQ_MEM_RECLAIM | WQ_PERCPU, 0);
        if (!user_dlm_worker) {
                status = -ENOMEM;
                goto bail;
        }
        cleanup_worker = 1;

        user_dlm_set_locking_protocol();
        status = register_filesystem(&dlmfs_fs_type);
bail:
        if (status) {
                if (cleanup_inode)
                        kmem_cache_destroy(dlmfs_inode_cache);
                if (cleanup_worker)
                        destroy_workqueue(user_dlm_worker);
        } else
                printk("OCFS2 User DLM kernel interface loaded\n");
        return status;
}

static void __exit exit_dlmfs_fs(void)
{
        unregister_filesystem(&dlmfs_fs_type);

        destroy_workqueue(user_dlm_worker);

        /*
         * Make sure all delayed rcu free inodes are flushed before we
         * destroy cache.
         */
        rcu_barrier();
        kmem_cache_destroy(dlmfs_inode_cache);

}

MODULE_AUTHOR("Oracle");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("OCFS2 DLM-Filesystem");

module_init(init_dlmfs_fs)
module_exit(exit_dlmfs_fs)