/*      $NetBSD: tmpfs_vfsops.c,v 1.78 2022/11/10 10:54:14 hannken Exp $        */

/*
 * Copyright (c) 2005, 2006, 2007 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Julio M. Merino Vidal, developed as part of Google's Summer of Code
 * 2005 program.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * Efficient memory file system.
 *
 * tmpfs is a file system that uses NetBSD's virtual memory sub-system
 * (the well-known UVM) to store file data and metadata in an efficient
 * way.  This means that it does not follow the structure of an on-disk
 * file system because it simply does not need to.  Instead, it uses
 * memory-specific data structures and algorithms to automatically
 * allocate and release resources.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: tmpfs_vfsops.c,v 1.78 2022/11/10 10:54:14 hannken Exp $");

#include <sys/param.h>
#include <sys/atomic.h>
#include <sys/types.h>
#include <sys/kmem.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/systm.h>
#include <sys/vnode.h>
#include <sys/kauth.h>
#include <sys/module.h>

#include <miscfs/genfs/genfs.h>
#include <fs/tmpfs/tmpfs.h>
#include <fs/tmpfs/tmpfs_args.h>

MODULE(MODULE_CLASS_VFS, tmpfs, NULL);

struct pool     tmpfs_dirent_pool;
struct pool     tmpfs_node_pool;

void
tmpfs_init(void)
{

        pool_init(&tmpfs_dirent_pool, sizeof(tmpfs_dirent_t), 0, 0, 0,
            "tmpfs_dirent", &pool_allocator_nointr, IPL_NONE);
        pool_init(&tmpfs_node_pool, sizeof(tmpfs_node_t), 0, 0, 0,
            "tmpfs_node", &pool_allocator_nointr, IPL_NONE);
}

void
tmpfs_done(void)
{

        pool_destroy(&tmpfs_dirent_pool);
        pool_destroy(&tmpfs_node_pool);
}

int
tmpfs_mount(struct mount *mp, const char *path, void *data, size_t *data_len)
{
        struct tmpfs_args *args = data;
        tmpfs_mount_t *tmp;
        tmpfs_node_t *root;
        struct vattr va;
        struct vnode *vp;
        uint64_t memlimit;
        ino_t nodes;
        int error, flags;
        bool set_memlimit;
        bool set_nodes;

        if (args == NULL)
                return EINVAL;

        /* Validate the version. */
        if (*data_len < sizeof(*args) ||
            args->ta_version != TMPFS_ARGS_VERSION)
                return EINVAL;

        /* Handle retrieval of mount point arguments. */
        if (mp->mnt_flag & MNT_GETARGS) {
                if (mp->mnt_data == NULL)
                        return EIO;
                tmp = VFS_TO_TMPFS(mp);

                args->ta_version = TMPFS_ARGS_VERSION;
                args->ta_nodes_max = tmp->tm_nodes_max;
                args->ta_size_max = tmp->tm_mem_limit;

                root = tmp->tm_root;
                args->ta_root_uid = root->tn_uid;
                args->ta_root_gid = root->tn_gid;
                args->ta_root_mode = root->tn_mode;

                *data_len = sizeof(*args);
                return 0;
        }


        /* Prohibit mounts if there is not enough memory. */
        if (tmpfs_mem_info(true) < uvmexp.freetarg)
                return EINVAL;

        /* Check for invalid uid and gid arguments */
        if (args->ta_root_uid == VNOVAL || args->ta_root_gid == VNOVAL)
                return EINVAL;

        /* Get the memory usage limit for this file-system. */
        if (args->ta_size_max < PAGE_SIZE) {
                memlimit = UINT64_MAX;
                set_memlimit = false;
        } else {
                memlimit = args->ta_size_max;
                set_memlimit = true;
        }
        KASSERT(memlimit > 0);

        if (args->ta_nodes_max <= 3) {
                nodes = 3 + (memlimit / 1024);
                set_nodes = false;
        } else {
                nodes = args->ta_nodes_max;
                set_nodes = true;
        }
        nodes = MIN(nodes, INT_MAX);
        KASSERT(nodes >= 3);

        if (mp->mnt_flag & MNT_UPDATE) {
                tmp = VFS_TO_TMPFS(mp);
                if (set_nodes && nodes < tmp->tm_nodes_cnt)
                        return EBUSY;
                if ((mp->mnt_iflag & IMNT_WANTRDONLY)) {
                        /* Changing from read/write to read-only. */
                        flags = WRITECLOSE;
                        if ((mp->mnt_flag & MNT_FORCE))
                                flags |= FORCECLOSE;
                        error = vflush(mp, NULL, flags);
                        if (error)
                                return error;
                }
                if (set_memlimit) {
                        if ((error = tmpfs_mntmem_set(tmp, memlimit)) != 0)
                                return error;
                }
                if (set_nodes)
                        tmp->tm_nodes_max = nodes;
                root = tmp->tm_root;
                root->tn_uid = args->ta_root_uid;
                root->tn_gid = args->ta_root_gid;
                root->tn_mode = args->ta_root_mode;
                return 0;
        }

        mp->mnt_flag |= MNT_LOCAL;
        mp->mnt_stat.f_namemax = TMPFS_MAXNAMLEN;
        mp->mnt_fs_bshift = PAGE_SHIFT;
        mp->mnt_dev_bshift = DEV_BSHIFT;
        mp->mnt_iflag |= IMNT_MPSAFE | IMNT_CAN_RWTORO | IMNT_SHRLOOKUP |
            IMNT_NCLOOKUP;
        vfs_getnewfsid(mp);

        /* Allocate the tmpfs mount structure and fill it. */
        tmp = kmem_zalloc(sizeof(tmpfs_mount_t), KM_SLEEP);
        tmp->tm_nodes_max = nodes;
        tmp->tm_nodes_cnt = 0;
        LIST_INIT(&tmp->tm_nodes);

        mutex_init(&tmp->tm_lock, MUTEX_DEFAULT, IPL_NONE);
        tmpfs_mntmem_init(tmp, memlimit);
        mp->mnt_data = tmp;

        error = set_statvfs_info(path, UIO_USERSPACE, "tmpfs", UIO_SYSSPACE,
            mp->mnt_op->vfs_name, mp, curlwp);
        if (error)
                goto errout;

        /* Allocate the root node. */
        vattr_null(&va);
        va.va_type = VDIR;
        va.va_mode = args->ta_root_mode & ALLPERMS;
        va.va_uid = args->ta_root_uid;
        va.va_gid = args->ta_root_gid;
        error = vcache_new(mp, NULL, &va, NOCRED, NULL, &vp);
        if (error)
                goto errout;
        KASSERT(vp != NULL);
        root = VP_TO_TMPFS_NODE(vp);
        KASSERT(root != NULL);

        /*
         * Parent of the root inode is itself.  Also, root inode has no
         * directory entry (i.e. is never attached), thus hold an extra
         * reference (link) for it.
         */
        root->tn_links++;
        root->tn_spec.tn_dir.tn_parent = root;
        tmp->tm_root = root;
        vrele(vp);

        return 0;

errout:
        mp->mnt_data = NULL;
        tmpfs_mntmem_destroy(tmp);
        mutex_destroy(&tmp->tm_lock);
        kmem_free(tmp, sizeof(*tmp));

        return error;
}

int
tmpfs_start(struct mount *mp, int flags)
{

        return 0;
}

int
tmpfs_unmount(struct mount *mp, int mntflags)
{
        tmpfs_mount_t *tmp = VFS_TO_TMPFS(mp);
        tmpfs_node_t *node, *cnode;
        int error, flags = 0;

        /* Handle forced unmounts. */
        if (mntflags & MNT_FORCE)
                flags |= FORCECLOSE;

        /* Finalize all pending I/O. */
        error = vflush(mp, NULL, flags);
        if (error != 0)
                return error;

        /*
         * First round, detach and destroy all directory entries.
         * Also, clear the pointers to the vnodes - they are gone.
         */
        LIST_FOREACH(node, &tmp->tm_nodes, tn_entries) {
                tmpfs_dirent_t *de;

                node->tn_vnode = NULL;
                if (node->tn_type != VDIR) {
                        continue;
                }
                while ((de = TAILQ_FIRST(&node->tn_spec.tn_dir.tn_dir)) != NULL) {
                        cnode = de->td_node;
                        if (cnode && cnode != TMPFS_NODE_WHITEOUT) {
                                cnode->tn_vnode = NULL;
                        }
                        tmpfs_dir_detach(node, de);
                        tmpfs_free_dirent(tmp, de);
                }
                /* Extra virtual entry (itself for the root). */
                node->tn_links--;
        }

        /* Release the reference on root (diagnostic). */
        node = tmp->tm_root;
        node->tn_links--;

        /* Second round, destroy all inodes. */
        while ((node = LIST_FIRST(&tmp->tm_nodes)) != NULL) {
                tmpfs_free_node(tmp, node);
        }

        /* Throw away the tmpfs_mount structure. */
        tmpfs_mntmem_destroy(tmp);
        mutex_destroy(&tmp->tm_lock);
        kmem_free(tmp, sizeof(*tmp));
        mp->mnt_data = NULL;

        return 0;
}

int
tmpfs_root(struct mount *mp, int lktype, vnode_t **vpp)
{
        tmpfs_node_t *node = VFS_TO_TMPFS(mp)->tm_root;
        int error;

        error = vcache_get(mp, &node, sizeof(node), vpp);
        if (error)
                return error;
        error = vn_lock(*vpp, lktype);
        if (error) {
                vrele(*vpp);
                *vpp = NULL;
                return error;
        }

        return 0;
}

int
tmpfs_vget(struct mount *mp, ino_t ino, int lktype, vnode_t **vpp)
{

        return EOPNOTSUPP;
}

int
tmpfs_fhtovp(struct mount *mp, struct fid *fhp, int lktype, vnode_t **vpp)
{
        tmpfs_mount_t *tmp = VFS_TO_TMPFS(mp);
        tmpfs_node_t *node;
        tmpfs_fid_t tfh;
        int error;

        if (fhp->fid_len != sizeof(tmpfs_fid_t)) {
                return EINVAL;
        }
        memcpy(&tfh, fhp, sizeof(tmpfs_fid_t));

        mutex_enter(&tmp->tm_lock);
        /* XXX big oof .. use a better data structure */
        LIST_FOREACH(node, &tmp->tm_nodes, tn_entries) {
                if (node->tn_id == tfh.tf_id) {
                        /* Prevent this node from disappearing. */
                        atomic_inc_32(&node->tn_holdcount);
                        break;
                }
        }
        mutex_exit(&tmp->tm_lock);
        if (node == NULL)
                return ESTALE;

        error = vcache_get(mp, &node, sizeof(node), vpp);
        /* If this node has been reclaimed free it now. */
        if (atomic_dec_32_nv(&node->tn_holdcount) == TMPFS_NODE_RECLAIMED) {
                KASSERT(error != 0);
                tmpfs_free_node(tmp, node);
        }
        if (error)
                return (error == ENOENT ? ESTALE : error);
        error = vn_lock(*vpp, lktype);
        if (error) {
                vrele(*vpp);
                *vpp = NULL;
                return error;
        }
        if (TMPFS_NODE_GEN(node) != tfh.tf_gen) {
                vput(*vpp);
                *vpp = NULL;
                return ESTALE;
        }

        return 0;
}

int
tmpfs_vptofh(vnode_t *vp, struct fid *fhp, size_t *fh_size)
{
        tmpfs_fid_t tfh;
        tmpfs_node_t *node;

        if (*fh_size < sizeof(tmpfs_fid_t)) {
                *fh_size = sizeof(tmpfs_fid_t);
                return E2BIG;
        }
        *fh_size = sizeof(tmpfs_fid_t);
        node = VP_TO_TMPFS_NODE(vp);

        memset(&tfh, 0, sizeof(tfh));
        tfh.tf_len = sizeof(tmpfs_fid_t);
        tfh.tf_gen = TMPFS_NODE_GEN(node);
        tfh.tf_id = node->tn_id;
        memcpy(fhp, &tfh, sizeof(tfh));

        return 0;
}

int
tmpfs_statvfs(struct mount *mp, struct statvfs *sbp)
{
        tmpfs_mount_t *tmp;
        fsfilcnt_t freenodes;
        size_t avail;

        tmp = VFS_TO_TMPFS(mp);

        sbp->f_iosize = sbp->f_frsize = sbp->f_bsize = PAGE_SIZE;

        mutex_enter(&tmp->tm_acc_lock);
        avail =  tmpfs_pages_avail(tmp);
        sbp->f_blocks = (tmpfs_bytes_max(tmp) >> PAGE_SHIFT);
        sbp->f_bavail = sbp->f_bfree = avail;
        sbp->f_bresvd = 0;

        freenodes = MIN(tmp->tm_nodes_max - tmp->tm_nodes_cnt,
            avail * PAGE_SIZE / sizeof(tmpfs_node_t));

        sbp->f_files = tmp->tm_nodes_cnt + freenodes;
        sbp->f_favail = sbp->f_ffree = freenodes;
        sbp->f_fresvd = 0;
        mutex_exit(&tmp->tm_acc_lock);

        copy_statvfs_info(sbp, mp);

        return 0;
}

int
tmpfs_sync(struct mount *mp, int waitfor, kauth_cred_t uc)
{

        return 0;
}

int
tmpfs_snapshot(struct mount *mp, vnode_t *vp, struct timespec *ctime)
{

        return EOPNOTSUPP;
}

/*
 * tmpfs vfs operations.
 */

extern const struct vnodeopv_desc tmpfs_fifoop_opv_desc;
extern const struct vnodeopv_desc tmpfs_specop_opv_desc;
extern const struct vnodeopv_desc tmpfs_vnodeop_opv_desc;

const struct vnodeopv_desc * const tmpfs_vnodeopv_descs[] = {
        &tmpfs_fifoop_opv_desc,
        &tmpfs_specop_opv_desc,
        &tmpfs_vnodeop_opv_desc,
        NULL,
};

struct vfsops tmpfs_vfsops = {
        .vfs_name = MOUNT_TMPFS,
        .vfs_min_mount_data = sizeof (struct tmpfs_args),
        .vfs_mount = tmpfs_mount,
        .vfs_start = tmpfs_start,
        .vfs_unmount = tmpfs_unmount,
        .vfs_root = tmpfs_root,
        .vfs_quotactl = (void *)eopnotsupp,
        .vfs_statvfs = tmpfs_statvfs,
        .vfs_sync = tmpfs_sync,
        .vfs_vget = tmpfs_vget,
        .vfs_loadvnode = tmpfs_loadvnode,
        .vfs_newvnode = tmpfs_newvnode,
        .vfs_fhtovp = tmpfs_fhtovp,
        .vfs_vptofh = tmpfs_vptofh,
        .vfs_init = tmpfs_init,
        .vfs_done = tmpfs_done,
        .vfs_snapshot = tmpfs_snapshot,
        .vfs_extattrctl = vfs_stdextattrctl,
        .vfs_suspendctl = genfs_suspendctl,
        .vfs_renamelock_enter = genfs_renamelock_enter,
        .vfs_renamelock_exit = genfs_renamelock_exit,
        .vfs_fsync = (void *)eopnotsupp,
        .vfs_opv_descs = tmpfs_vnodeopv_descs
};

static int
tmpfs_modcmd(modcmd_t cmd, void *arg)
{

        switch (cmd) {
        case MODULE_CMD_INIT:
                return vfs_attach(&tmpfs_vfsops);
        case MODULE_CMD_FINI:
                return vfs_detach(&tmpfs_vfsops);
        default:
                return ENOTTY;
        }
}