/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2008  Miklos Szeredi <miklos@szeredi.hu>

  This program can be distributed under the terms of the GNU GPL.
  See the file COPYING.
*/

#include "fuse_i.h"

#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/seq_file.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/fs_context.h>
#include <linux/fs_parser.h>
#include <linux/statfs.h>
#include <linux/random.h>
#include <linux/sched.h>
#include <linux/exportfs.h>
#include <linux/posix_acl.h>
#include <linux/pid_namespace.h>

MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
MODULE_DESCRIPTION("Filesystem in Userspace");
MODULE_LICENSE("GPL");

static struct kmem_cache *fuse_inode_cachep;
struct list_head fuse_conn_list;
DEFINE_MUTEX(fuse_mutex);

static int set_global_limit(const char *val, const struct kernel_param *kp);

unsigned max_user_bgreq;
module_param_call(max_user_bgreq, set_global_limit, param_get_uint,
                  &max_user_bgreq, 0644);
__MODULE_PARM_TYPE(max_user_bgreq, "uint");
MODULE_PARM_DESC(max_user_bgreq,
 "Global limit for the maximum number of backgrounded requests an "
 "unprivileged user can set");

unsigned max_user_congthresh;
module_param_call(max_user_congthresh, set_global_limit, param_get_uint,
                  &max_user_congthresh, 0644);
__MODULE_PARM_TYPE(max_user_congthresh, "uint");
MODULE_PARM_DESC(max_user_congthresh,
 "Global limit for the maximum congestion threshold an "
 "unprivileged user can set");

#define FUSE_SUPER_MAGIC 0x65735546

#define FUSE_DEFAULT_BLKSIZE 512

/** Maximum number of outstanding background requests */
#define FUSE_DEFAULT_MAX_BACKGROUND 12

/** Congestion starts at 75% of maximum */
#define FUSE_DEFAULT_CONGESTION_THRESHOLD (FUSE_DEFAULT_MAX_BACKGROUND * 3 / 4)

#ifdef CONFIG_BLOCK
static struct file_system_type fuseblk_fs_type;
#endif

struct fuse_forget_link *fuse_alloc_forget(void)
{
        return kzalloc(sizeof(struct fuse_forget_link), GFP_KERNEL_ACCOUNT);
}

static struct inode *fuse_alloc_inode(struct super_block *sb)
{
        struct fuse_inode *fi;

        fi = kmem_cache_alloc(fuse_inode_cachep, GFP_KERNEL);
        if (!fi)
                return NULL;

        fi->i_time = 0;
        fi->inval_mask = 0;
        fi->nodeid = 0;
        fi->nlookup = 0;
        fi->attr_version = 0;
        fi->orig_ino = 0;
        fi->state = 0;
        mutex_init(&fi->mutex);
        spin_lock_init(&fi->lock);
        fi->forget = fuse_alloc_forget();
        if (!fi->forget)
                goto out_free;

        if (IS_ENABLED(CONFIG_FUSE_DAX) && !fuse_dax_inode_alloc(sb, fi))
                goto out_free_forget;

        return &fi->inode;

out_free_forget:
        kfree(fi->forget);
out_free:
        kmem_cache_free(fuse_inode_cachep, fi);
        return NULL;
}

static void fuse_free_inode(struct inode *inode)
{
        struct fuse_inode *fi = get_fuse_inode(inode);

        mutex_destroy(&fi->mutex);
        kfree(fi->forget);
#ifdef CONFIG_FUSE_DAX
        kfree(fi->dax);
#endif
        kmem_cache_free(fuse_inode_cachep, fi);
}

static void fuse_evict_inode(struct inode *inode)
{
        struct fuse_inode *fi = get_fuse_inode(inode);

        truncate_inode_pages_final(&inode->i_data);
        clear_inode(inode);
        if (inode->i_sb->s_flags & SB_ACTIVE) {
                struct fuse_conn *fc = get_fuse_conn(inode);

                if (FUSE_IS_DAX(inode))
                        fuse_dax_inode_cleanup(inode);
                if (fi->nlookup) {
                        fuse_queue_forget(fc, fi->forget, fi->nodeid,
                                          fi->nlookup);
                        fi->forget = NULL;
                }
        }
        if (S_ISREG(inode->i_mode) && !fuse_is_bad(inode)) {
                WARN_ON(!list_empty(&fi->write_files));
                WARN_ON(!list_empty(&fi->queued_writes));
        }
}

static int fuse_reconfigure(struct fs_context *fsc)
{
        struct super_block *sb = fsc->root->d_sb;

        sync_filesystem(sb);
        if (fsc->sb_flags & SB_MANDLOCK)
                return -EINVAL;

        return 0;
}

/*
 * ino_t is 32-bits on 32-bit arch. We have to squash the 64-bit value down
 * so that it will fit.
 */
static ino_t fuse_squash_ino(u64 ino64)
{
        ino_t ino = (ino_t) ino64;
        if (sizeof(ino_t) < sizeof(u64))
                ino ^= ino64 >> (sizeof(u64) - sizeof(ino_t)) * 8;
        return ino;
}

void fuse_change_attributes_common(struct inode *inode, struct fuse_attr *attr,
                                   u64 attr_valid)
{
        struct fuse_conn *fc = get_fuse_conn(inode);
        struct fuse_inode *fi = get_fuse_inode(inode);

        lockdep_assert_held(&fi->lock);

        fi->attr_version = atomic64_inc_return(&fc->attr_version);
        fi->i_time = attr_valid;
        WRITE_ONCE(fi->inval_mask, 0);

        inode->i_ino     = fuse_squash_ino(attr->ino);
        inode->i_mode    = (inode->i_mode & S_IFMT) | (attr->mode & 07777);
        set_nlink(inode, attr->nlink);
        inode->i_uid     = make_kuid(fc->user_ns, attr->uid);
        inode->i_gid     = make_kgid(fc->user_ns, attr->gid);
        inode->i_blocks  = attr->blocks;
        inode->i_atime.tv_sec   = attr->atime;
        inode->i_atime.tv_nsec  = attr->atimensec;
        /* mtime from server may be stale due to local buffered write */
        if (!fc->writeback_cache || !S_ISREG(inode->i_mode)) {
                inode->i_mtime.tv_sec   = attr->mtime;
                inode->i_mtime.tv_nsec  = attr->mtimensec;
                inode->i_ctime.tv_sec   = attr->ctime;
                inode->i_ctime.tv_nsec  = attr->ctimensec;
        }

        if (attr->blksize != 0)
                inode->i_blkbits = ilog2(attr->blksize);
        else
                inode->i_blkbits = inode->i_sb->s_blocksize_bits;

        /*
         * Don't set the sticky bit in i_mode, unless we want the VFS
         * to check permissions.  This prevents failures due to the
         * check in may_delete().
         */
        fi->orig_i_mode = inode->i_mode;
        if (!fc->default_permissions)
                inode->i_mode &= ~S_ISVTX;

        fi->orig_ino = attr->ino;

        /*
         * We are refreshing inode data and it is possible that another
         * client set suid/sgid or security.capability xattr. So clear
         * S_NOSEC. Ideally, we could have cleared it only if suid/sgid
         * was set or if security.capability xattr was set. But we don't
         * know if security.capability has been set or not. So clear it
         * anyway. Its less efficient but should be safe.
         */
        inode->i_flags &= ~S_NOSEC;
}

void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
                            u64 attr_valid, u64 attr_version)
{
        struct fuse_conn *fc = get_fuse_conn(inode);
        struct fuse_inode *fi = get_fuse_inode(inode);
        bool is_wb = fc->writeback_cache;
        loff_t oldsize;
        struct timespec64 old_mtime;

        spin_lock(&fi->lock);
        if ((attr_version != 0 && fi->attr_version > attr_version) ||
            test_bit(FUSE_I_SIZE_UNSTABLE, &fi->state)) {
                spin_unlock(&fi->lock);
                return;
        }

        old_mtime = inode->i_mtime;
        fuse_change_attributes_common(inode, attr, attr_valid);

        oldsize = inode->i_size;
        /*
         * In case of writeback_cache enabled, the cached writes beyond EOF
         * extend local i_size without keeping userspace server in sync. So,
         * attr->size coming from server can be stale. We cannot trust it.
         */
        if (!is_wb || !S_ISREG(inode->i_mode))
                i_size_write(inode, attr->size);
        spin_unlock(&fi->lock);

        if (!is_wb && S_ISREG(inode->i_mode)) {
                bool inval = false;

                if (oldsize != attr->size) {
                        truncate_pagecache(inode, attr->size);
                        if (!fc->explicit_inval_data)
                                inval = true;
                } else if (fc->auto_inval_data) {
                        struct timespec64 new_mtime = {
                                .tv_sec = attr->mtime,
                                .tv_nsec = attr->mtimensec,
                        };

                        /*
                         * Auto inval mode also checks and invalidates if mtime
                         * has changed.
                         */
                        if (!timespec64_equal(&old_mtime, &new_mtime))
                                inval = true;
                }

                if (inval)
                        invalidate_inode_pages2(inode->i_mapping);
        }
}

static void fuse_init_inode(struct inode *inode, struct fuse_attr *attr)
{
        inode->i_mode = attr->mode & S_IFMT;
        inode->i_size = attr->size;
        inode->i_mtime.tv_sec  = attr->mtime;
        inode->i_mtime.tv_nsec = attr->mtimensec;
        inode->i_ctime.tv_sec  = attr->ctime;
        inode->i_ctime.tv_nsec = attr->ctimensec;
        if (S_ISREG(inode->i_mode)) {
                fuse_init_common(inode);
                fuse_init_file_inode(inode);
        } else if (S_ISDIR(inode->i_mode))
                fuse_init_dir(inode);
        else if (S_ISLNK(inode->i_mode))
                fuse_init_symlink(inode);
        else if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode) ||
                 S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
                fuse_init_common(inode);
                init_special_inode(inode, inode->i_mode,
                                   new_decode_dev(attr->rdev));
        } else
                BUG();
}

static int fuse_inode_eq(struct inode *inode, void *_nodeidp)
{
        u64 nodeid = *(u64 *) _nodeidp;
        if (get_node_id(inode) == nodeid)
                return 1;
        else
                return 0;
}

static int fuse_inode_set(struct inode *inode, void *_nodeidp)
{
        u64 nodeid = *(u64 *) _nodeidp;
        get_fuse_inode(inode)->nodeid = nodeid;
        return 0;
}

struct inode *fuse_iget(struct super_block *sb, u64 nodeid,
                        int generation, struct fuse_attr *attr,
                        u64 attr_valid, u64 attr_version)
{
        struct inode *inode;
        struct fuse_inode *fi;
        struct fuse_conn *fc = get_fuse_conn_super(sb);

        /*
         * Auto mount points get their node id from the submount root, which is
         * not a unique identifier within this filesystem.
         *
         * To avoid conflicts, do not place submount points into the inode hash
         * table.
         */
        if (fc->auto_submounts && (attr->flags & FUSE_ATTR_SUBMOUNT) &&
            S_ISDIR(attr->mode)) {
                inode = new_inode(sb);
                if (!inode)
                        return NULL;

                fuse_init_inode(inode, attr);
                get_fuse_inode(inode)->nodeid = nodeid;
                inode->i_flags |= S_AUTOMOUNT;
                goto done;
        }

retry:
        inode = iget5_locked(sb, nodeid, fuse_inode_eq, fuse_inode_set, &nodeid);
        if (!inode)
                return NULL;

        if ((inode->i_state & I_NEW)) {
                inode->i_flags |= S_NOATIME;
                if (!fc->writeback_cache || !S_ISREG(attr->mode))
                        inode->i_flags |= S_NOCMTIME;
                inode->i_generation = generation;
                fuse_init_inode(inode, attr);
                unlock_new_inode(inode);
        } else if (fuse_stale_inode(inode, generation, attr)) {
                /* nodeid was reused, any I/O on the old inode should fail */
                fuse_make_bad(inode);
                iput(inode);
                goto retry;
        }
done:
        fi = get_fuse_inode(inode);
        spin_lock(&fi->lock);
        fi->nlookup++;
        spin_unlock(&fi->lock);
        fuse_change_attributes(inode, attr, attr_valid, attr_version);

        return inode;
}

struct inode *fuse_ilookup(struct fuse_conn *fc, u64 nodeid,
                           struct fuse_mount **fm)
{
        struct fuse_mount *fm_iter;
        struct inode *inode;

        WARN_ON(!rwsem_is_locked(&fc->killsb));
        list_for_each_entry(fm_iter, &fc->mounts, fc_entry) {
                if (!fm_iter->sb)
                        continue;

                inode = ilookup5(fm_iter->sb, nodeid, fuse_inode_eq, &nodeid);
                if (inode) {
                        if (fm)
                                *fm = fm_iter;
                        return inode;
                }
        }

        return NULL;
}

int fuse_reverse_inval_inode(struct fuse_conn *fc, u64 nodeid,
                             loff_t offset, loff_t len)
{
        struct fuse_inode *fi;
        struct inode *inode;
        pgoff_t pg_start;
        pgoff_t pg_end;

        inode = fuse_ilookup(fc, nodeid, NULL);
        if (!inode)
                return -ENOENT;

        fi = get_fuse_inode(inode);
        spin_lock(&fi->lock);
        fi->attr_version = atomic64_inc_return(&fc->attr_version);
        spin_unlock(&fi->lock);

        fuse_invalidate_attr(inode);
        forget_all_cached_acls(inode);
        if (offset >= 0) {
                pg_start = offset >> PAGE_SHIFT;
                if (len <= 0)
                        pg_end = -1;
                else
                        pg_end = (offset + len - 1) >> PAGE_SHIFT;
                invalidate_inode_pages2_range(inode->i_mapping,
                                              pg_start, pg_end);
        }
        iput(inode);
        return 0;
}

bool fuse_lock_inode(struct inode *inode)
{
        bool locked = false;

        if (!get_fuse_conn(inode)->parallel_dirops) {
                mutex_lock(&get_fuse_inode(inode)->mutex);
                locked = true;
        }

        return locked;
}

void fuse_unlock_inode(struct inode *inode, bool locked)
{
        if (locked)
                mutex_unlock(&get_fuse_inode(inode)->mutex);
}

static void fuse_umount_begin(struct super_block *sb)
{
        struct fuse_conn *fc = get_fuse_conn_super(sb);

        if (!fc->no_force_umount)
                fuse_abort_conn(fc);
}

static void fuse_send_destroy(struct fuse_mount *fm)
{
        if (fm->fc->conn_init) {
                FUSE_ARGS(args);

                args.opcode = FUSE_DESTROY;
                args.force = true;
                args.nocreds = true;
                fuse_simple_request(fm, &args);
        }
}

static void convert_fuse_statfs(struct kstatfs *stbuf, struct fuse_kstatfs *attr)
{
        stbuf->f_type    = FUSE_SUPER_MAGIC;
        stbuf->f_bsize   = attr->bsize;
        stbuf->f_frsize  = attr->frsize;
        stbuf->f_blocks  = attr->blocks;
        stbuf->f_bfree   = attr->bfree;
        stbuf->f_bavail  = attr->bavail;
        stbuf->f_files   = attr->files;
        stbuf->f_ffree   = attr->ffree;
        stbuf->f_namelen = attr->namelen;
        /* fsid is left zero */
}

static int fuse_statfs(struct dentry *dentry, struct kstatfs *buf)
{
        struct super_block *sb = dentry->d_sb;
        struct fuse_mount *fm = get_fuse_mount_super(sb);
        FUSE_ARGS(args);
        struct fuse_statfs_out outarg;
        int err;

        if (!fuse_allow_current_process(fm->fc)) {
                buf->f_type = FUSE_SUPER_MAGIC;
                return 0;
        }

        memset(&outarg, 0, sizeof(outarg));
        args.in_numargs = 0;
        args.opcode = FUSE_STATFS;
        args.nodeid = get_node_id(d_inode(dentry));
        args.out_numargs = 1;
        args.out_args[0].size = sizeof(outarg);
        args.out_args[0].value = &outarg;
        err = fuse_simple_request(fm, &args);
        if (!err)
                convert_fuse_statfs(buf, &outarg.st);
        return err;
}

static struct fuse_sync_bucket *fuse_sync_bucket_alloc(void)
{
        struct fuse_sync_bucket *bucket;

        bucket = kzalloc(sizeof(*bucket), GFP_KERNEL | __GFP_NOFAIL);
        if (bucket) {
                init_waitqueue_head(&bucket->waitq);
                /* Initial active count */
                atomic_set(&bucket->count, 1);
        }
        return bucket;
}

static void fuse_sync_fs_writes(struct fuse_conn *fc)
{
        struct fuse_sync_bucket *bucket, *new_bucket;
        int count;

        new_bucket = fuse_sync_bucket_alloc();
        spin_lock(&fc->lock);
        bucket = rcu_dereference_protected(fc->curr_bucket, 1);
        count = atomic_read(&bucket->count);
        WARN_ON(count < 1);
        /* No outstanding writes? */
        if (count == 1) {
                spin_unlock(&fc->lock);
                kfree(new_bucket);
                return;
        }

        /*
         * Completion of new bucket depends on completion of this bucket, so add
         * one more count.
         */
        atomic_inc(&new_bucket->count);
        rcu_assign_pointer(fc->curr_bucket, new_bucket);
        spin_unlock(&fc->lock);
        /*
         * Drop initial active count.  At this point if all writes in this and
         * ancestor buckets complete, the count will go to zero and this task
         * will be woken up.
         */
        atomic_dec(&bucket->count);

        wait_event(bucket->waitq, atomic_read(&bucket->count) == 0);

        /* Drop temp count on descendant bucket */
        fuse_sync_bucket_dec(new_bucket);
        kfree_rcu(bucket, rcu);
}

static int fuse_sync_fs(struct super_block *sb, int wait)
{
        struct fuse_mount *fm = get_fuse_mount_super(sb);
        struct fuse_conn *fc = fm->fc;
        struct fuse_syncfs_in inarg;
        FUSE_ARGS(args);
        int err;

        /*
         * Userspace cannot handle the wait == 0 case.  Avoid a
         * gratuitous roundtrip.
         */
        if (!wait)
                return 0;

        /* The filesystem is being unmounted.  Nothing to do. */
        if (!sb->s_root)
                return 0;

        if (!fc->sync_fs)
                return 0;

        fuse_sync_fs_writes(fc);

        memset(&inarg, 0, sizeof(inarg));
        args.in_numargs = 1;
        args.in_args[0].size = sizeof(inarg);
        args.in_args[0].value = &inarg;
        args.opcode = FUSE_SYNCFS;
        args.nodeid = get_node_id(sb->s_root->d_inode);
        args.out_numargs = 0;

        err = fuse_simple_request(fm, &args);
        if (err == -ENOSYS) {
                fc->sync_fs = 0;
                err = 0;
        }

        return err;
}

enum {
        OPT_SOURCE,
        OPT_SUBTYPE,
        OPT_FD,
        OPT_ROOTMODE,
        OPT_USER_ID,
        OPT_GROUP_ID,
        OPT_DEFAULT_PERMISSIONS,
        OPT_ALLOW_OTHER,
        OPT_MAX_READ,
        OPT_BLKSIZE,
        OPT_ERR
};

static const struct fs_parameter_spec fuse_fs_parameters[] = {
        fsparam_string  ("source",              OPT_SOURCE),
        fsparam_u32     ("fd",                  OPT_FD),
        fsparam_u32oct  ("rootmode",            OPT_ROOTMODE),
        fsparam_u32     ("user_id",             OPT_USER_ID),
        fsparam_u32     ("group_id",            OPT_GROUP_ID),
        fsparam_flag    ("default_permissions", OPT_DEFAULT_PERMISSIONS),
        fsparam_flag    ("allow_other",         OPT_ALLOW_OTHER),
        fsparam_u32     ("max_read",            OPT_MAX_READ),
        fsparam_u32     ("blksize",             OPT_BLKSIZE),
        fsparam_string  ("subtype",             OPT_SUBTYPE),
        {}
};

static int fuse_parse_param(struct fs_context *fsc, struct fs_parameter *param)
{
        struct fs_parse_result result;
        struct fuse_fs_context *ctx = fsc->fs_private;
        int opt;

        if (fsc->purpose == FS_CONTEXT_FOR_RECONFIGURE) {
                /*
                 * Ignore options coming from mount(MS_REMOUNT) for backward
                 * compatibility.
                 */
                if (fsc->oldapi)
                        return 0;

                return invalfc(fsc, "No changes allowed in reconfigure");
        }

        opt = fs_parse(fsc, fuse_fs_parameters, param, &result);
        if (opt < 0)
                return opt;

        switch (opt) {
        case OPT_SOURCE:
                if (fsc->source)
                        return invalfc(fsc, "Multiple sources specified");
                fsc->source = param->string;
                param->string = NULL;
                break;

        case OPT_SUBTYPE:
                if (ctx->subtype)
                        return invalfc(fsc, "Multiple subtypes specified");
                ctx->subtype = param->string;
                param->string = NULL;
                return 0;

        case OPT_FD:
                ctx->fd = result.uint_32;
                ctx->fd_present = true;
                break;

        case OPT_ROOTMODE:
                if (!fuse_valid_type(result.uint_32))
                        return invalfc(fsc, "Invalid rootmode");
                ctx->rootmode = result.uint_32;
                ctx->rootmode_present = true;
                break;

        case OPT_USER_ID:
                ctx->user_id = make_kuid(fsc->user_ns, result.uint_32);
                if (!uid_valid(ctx->user_id))
                        return invalfc(fsc, "Invalid user_id");
                ctx->user_id_present = true;
                break;

        case OPT_GROUP_ID:
                ctx->group_id = make_kgid(fsc->user_ns, result.uint_32);
                if (!gid_valid(ctx->group_id))
                        return invalfc(fsc, "Invalid group_id");
                ctx->group_id_present = true;
                break;

        case OPT_DEFAULT_PERMISSIONS:
                ctx->default_permissions = true;
                break;

        case OPT_ALLOW_OTHER:
                ctx->allow_other = true;
                break;

        case OPT_MAX_READ:
                ctx->max_read = result.uint_32;
                break;

        case OPT_BLKSIZE:
                if (!ctx->is_bdev)
                        return invalfc(fsc, "blksize only supported for fuseblk");
                ctx->blksize = result.uint_32;
                break;

        default:
                return -EINVAL;
        }

        return 0;
}

static void fuse_free_fsc(struct fs_context *fsc)
{
        struct fuse_fs_context *ctx = fsc->fs_private;

        if (ctx) {
                kfree(ctx->subtype);
                kfree(ctx);
        }
}

static int fuse_show_options(struct seq_file *m, struct dentry *root)
{
        struct super_block *sb = root->d_sb;
        struct fuse_conn *fc = get_fuse_conn_super(sb);

        if (fc->legacy_opts_show) {
                seq_printf(m, ",user_id=%u",
                           from_kuid_munged(fc->user_ns, fc->user_id));
                seq_printf(m, ",group_id=%u",
                           from_kgid_munged(fc->user_ns, fc->group_id));
                if (fc->default_permissions)
                        seq_puts(m, ",default_permissions");
                if (fc->allow_other)
                        seq_puts(m, ",allow_other");
                if (fc->max_read != ~0)
                        seq_printf(m, ",max_read=%u", fc->max_read);
                if (sb->s_bdev && sb->s_blocksize != FUSE_DEFAULT_BLKSIZE)
                        seq_printf(m, ",blksize=%lu", sb->s_blocksize);
        }
#ifdef CONFIG_FUSE_DAX
        if (fc->dax)
                seq_puts(m, ",dax");
#endif

        return 0;
}

static void fuse_iqueue_init(struct fuse_iqueue *fiq,
                             const struct fuse_iqueue_ops *ops,
                             void *priv)
{
        memset(fiq, 0, sizeof(struct fuse_iqueue));
        spin_lock_init(&fiq->lock);
        init_waitqueue_head(&fiq->waitq);
        INIT_LIST_HEAD(&fiq->pending);
        INIT_LIST_HEAD(&fiq->interrupts);
        fiq->forget_list_tail = &fiq->forget_list_head;
        fiq->connected = 1;
        fiq->ops = ops;
        fiq->priv = priv;
}

static void fuse_pqueue_init(struct fuse_pqueue *fpq)
{
        unsigned int i;

        spin_lock_init(&fpq->lock);
        for (i = 0; i < FUSE_PQ_HASH_SIZE; i++)
                INIT_LIST_HEAD(&fpq->processing[i]);
        INIT_LIST_HEAD(&fpq->io);
        fpq->connected = 1;
}

void fuse_conn_init(struct fuse_conn *fc, struct fuse_mount *fm,
                    struct user_namespace *user_ns,
                    const struct fuse_iqueue_ops *fiq_ops, void *fiq_priv)
{
        memset(fc, 0, sizeof(*fc));
        spin_lock_init(&fc->lock);
        spin_lock_init(&fc->bg_lock);
        init_rwsem(&fc->killsb);
        refcount_set(&fc->count, 1);
        atomic_set(&fc->dev_count, 1);
        init_waitqueue_head(&fc->blocked_waitq);
        fuse_iqueue_init(&fc->iq, fiq_ops, fiq_priv);
        INIT_LIST_HEAD(&fc->bg_queue);
        INIT_LIST_HEAD(&fc->entry);
        INIT_LIST_HEAD(&fc->devices);
        atomic_set(&fc->num_waiting, 0);
        fc->max_background = FUSE_DEFAULT_MAX_BACKGROUND;
        fc->congestion_threshold = FUSE_DEFAULT_CONGESTION_THRESHOLD;
        atomic64_set(&fc->khctr, 0);
        fc->polled_files = RB_ROOT;
        fc->blocked = 0;
        fc->initialized = 0;
        fc->connected = 1;
        atomic64_set(&fc->attr_version, 1);
        get_random_bytes(&fc->scramble_key, sizeof(fc->scramble_key));
        fc->pid_ns = get_pid_ns(task_active_pid_ns(current));
        fc->user_ns = get_user_ns(user_ns);
        fc->max_pages = FUSE_DEFAULT_MAX_PAGES_PER_REQ;
        fc->max_pages_limit = FUSE_MAX_MAX_PAGES;

        INIT_LIST_HEAD(&fc->mounts);
        list_add(&fm->fc_entry, &fc->mounts);
        fm->fc = fc;
}
EXPORT_SYMBOL_GPL(fuse_conn_init);

void fuse_conn_put(struct fuse_conn *fc)
{
        if (refcount_dec_and_test(&fc->count)) {
                struct fuse_iqueue *fiq = &fc->iq;
                struct fuse_sync_bucket *bucket;

                if (IS_ENABLED(CONFIG_FUSE_DAX))
                        fuse_dax_conn_free(fc);
                if (fiq->ops->release)
                        fiq->ops->release(fiq);
                put_pid_ns(fc->pid_ns);
                put_user_ns(fc->user_ns);
                bucket = rcu_dereference_protected(fc->curr_bucket, 1);
                if (bucket) {
                        WARN_ON(atomic_read(&bucket->count) != 1);
                        kfree(bucket);
                }
                fc->release(fc);
        }
}
EXPORT_SYMBOL_GPL(fuse_conn_put);

struct fuse_conn *fuse_conn_get(struct fuse_conn *fc)
{
        refcount_inc(&fc->count);
        return fc;
}
EXPORT_SYMBOL_GPL(fuse_conn_get);

static struct inode *fuse_get_root_inode(struct super_block *sb, unsigned mode)
{
        struct fuse_attr attr;
        memset(&attr, 0, sizeof(attr));

        attr.mode = mode;
        attr.ino = FUSE_ROOT_ID;
        attr.nlink = 1;
        return fuse_iget(sb, 1, 0, &attr, 0, 0);
}

struct fuse_inode_handle {
        u64 nodeid;
        u32 generation;
};

static struct dentry *fuse_get_dentry(struct super_block *sb,
                                      struct fuse_inode_handle *handle)
{
        struct fuse_conn *fc = get_fuse_conn_super(sb);
        struct inode *inode;
        struct dentry *entry;
        int err = -ESTALE;

        if (handle->nodeid == 0)
                goto out_err;

        inode = ilookup5(sb, handle->nodeid, fuse_inode_eq, &handle->nodeid);
        if (!inode) {
                struct fuse_entry_out outarg;
                const struct qstr name = QSTR_INIT(".", 1);

                if (!fc->export_support)
                        goto out_err;

                err = fuse_lookup_name(sb, handle->nodeid, &name, &outarg,
                                       &inode);
                if (err && err != -ENOENT)
                        goto out_err;
                if (err || !inode) {
                        err = -ESTALE;
                        goto out_err;
                }
                err = -EIO;
                if (get_node_id(inode) != handle->nodeid)
                        goto out_iput;
        }
        err = -ESTALE;
        if (inode->i_generation != handle->generation)
                goto out_iput;

        entry = d_obtain_alias(inode);
        if (!IS_ERR(entry) && get_node_id(inode) != FUSE_ROOT_ID)
                fuse_invalidate_entry_cache(entry);

        return entry;

 out_iput:
        iput(inode);
 out_err:
        return ERR_PTR(err);
}

static int fuse_encode_fh(struct inode *inode, u32 *fh, int *max_len,
                           struct inode *parent)
{
        int len = parent ? 6 : 3;
        u64 nodeid;
        u32 generation;

        if (*max_len < len) {
                *max_len = len;
                return  FILEID_INVALID;
        }

        nodeid = get_fuse_inode(inode)->nodeid;
        generation = inode->i_generation;

        fh[0] = (u32)(nodeid >> 32);
        fh[1] = (u32)(nodeid & 0xffffffff);
        fh[2] = generation;

        if (parent) {
                nodeid = get_fuse_inode(parent)->nodeid;
                generation = parent->i_generation;

                fh[3] = (u32)(nodeid >> 32);
                fh[4] = (u32)(nodeid & 0xffffffff);
                fh[5] = generation;
        }

        *max_len = len;
        return parent ? 0x82 : 0x81;
}

static struct dentry *fuse_fh_to_dentry(struct super_block *sb,
                struct fid *fid, int fh_len, int fh_type)
{
        struct fuse_inode_handle handle;

        if ((fh_type != 0x81 && fh_type != 0x82) || fh_len < 3)
                return NULL;

        handle.nodeid = (u64) fid->raw[0] << 32;
        handle.nodeid |= (u64) fid->raw[1];
        handle.generation = fid->raw[2];
        return fuse_get_dentry(sb, &handle);
}

static struct dentry *fuse_fh_to_parent(struct super_block *sb,
                struct fid *fid, int fh_len, int fh_type)
{
        struct fuse_inode_handle parent;

        if (fh_type != 0x82 || fh_len < 6)
                return NULL;

        parent.nodeid = (u64) fid->raw[3] << 32;
        parent.nodeid |= (u64) fid->raw[4];
        parent.generation = fid->raw[5];
        return fuse_get_dentry(sb, &parent);
}

static struct dentry *fuse_get_parent(struct dentry *child)
{
        struct inode *child_inode = d_inode(child);
        struct fuse_conn *fc = get_fuse_conn(child_inode);
        struct inode *inode;
        struct dentry *parent;
        struct fuse_entry_out outarg;
        int err;

        if (!fc->export_support)
                return ERR_PTR(-ESTALE);

        err = fuse_lookup_name(child_inode->i_sb, get_node_id(child_inode),
                               &dotdot_name, &outarg, &inode);
        if (err) {
                if (err == -ENOENT)
                        return ERR_PTR(-ESTALE);
                return ERR_PTR(err);
        }

        parent = d_obtain_alias(inode);
        if (!IS_ERR(parent) && get_node_id(inode) != FUSE_ROOT_ID)
                fuse_invalidate_entry_cache(parent);

        return parent;
}

static const struct export_operations fuse_export_operations = {
        .fh_to_dentry   = fuse_fh_to_dentry,
        .fh_to_parent   = fuse_fh_to_parent,
        .encode_fh      = fuse_encode_fh,
        .get_parent     = fuse_get_parent,
};

static const struct super_operations fuse_super_operations = {
        .alloc_inode    = fuse_alloc_inode,
        .free_inode     = fuse_free_inode,
        .evict_inode    = fuse_evict_inode,
        .write_inode    = fuse_write_inode,
        .drop_inode     = generic_delete_inode,
        .umount_begin   = fuse_umount_begin,
        .statfs         = fuse_statfs,
        .sync_fs        = fuse_sync_fs,

        .show_options   = fuse_show_options,
};

static void sanitize_global_limit(unsigned *limit)
{
        /*
         * The default maximum number of async requests is calculated to consume
         * 1/2^13 of the total memory, assuming 392 bytes per request.
         */
        if (*limit == 0)
                *limit = ((totalram_pages() << PAGE_SHIFT) >> 13) / 392;

        if (*limit >= 1 << 16)
                *limit = (1 << 16) - 1;
}

static int set_global_limit(const char *val, const struct kernel_param *kp)
{
        int rv;

        rv = param_set_uint(val, kp);
        if (rv)
                return rv;

        sanitize_global_limit((unsigned *)kp->arg);

        return 0;
}

static void process_init_limits(struct fuse_conn *fc, struct fuse_init_out *arg)
{
        int cap_sys_admin = capable(CAP_SYS_ADMIN);

        if (arg->minor < 13)
                return;

        sanitize_global_limit(&max_user_bgreq);
        sanitize_global_limit(&max_user_congthresh);

        spin_lock(&fc->bg_lock);
        if (arg->max_background) {
                fc->max_background = arg->max_background;

                if (!cap_sys_admin && fc->max_background > max_user_bgreq)
                        fc->max_background = max_user_bgreq;
        }
        if (arg->congestion_threshold) {
                fc->congestion_threshold = arg->congestion_threshold;

                if (!cap_sys_admin &&
                    fc->congestion_threshold > max_user_congthresh)
                        fc->congestion_threshold = max_user_congthresh;
        }
        spin_unlock(&fc->bg_lock);
}

struct fuse_init_args {
        struct fuse_args args;
        struct fuse_init_in in;
        struct fuse_init_out out;
};

static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args,
                               int error)
{
        struct fuse_conn *fc = fm->fc;
        struct fuse_init_args *ia = container_of(args, typeof(*ia), args);
        struct fuse_init_out *arg = &ia->out;
        bool ok = true;

        if (error || arg->major != FUSE_KERNEL_VERSION)
                ok = false;
        else {
                unsigned long ra_pages;

                process_init_limits(fc, arg);

                if (arg->minor >= 6) {
                        ra_pages = arg->max_readahead / PAGE_SIZE;
                        if (arg->flags & FUSE_ASYNC_READ)
                                fc->async_read = 1;
                        if (!(arg->flags & FUSE_POSIX_LOCKS))
                                fc->no_lock = 1;
                        if (arg->minor >= 17) {
                                if (!(arg->flags & FUSE_FLOCK_LOCKS))
                                        fc->no_flock = 1;
                        } else {
                                if (!(arg->flags & FUSE_POSIX_LOCKS))
                                        fc->no_flock = 1;
                        }
                        if (arg->flags & FUSE_ATOMIC_O_TRUNC)
                                fc->atomic_o_trunc = 1;
                        if (arg->minor >= 9) {
                                /* LOOKUP has dependency on proto version */
                                if (arg->flags & FUSE_EXPORT_SUPPORT)
                                        fc->export_support = 1;
                        }
                        if (arg->flags & FUSE_BIG_WRITES)
                                fc->big_writes = 1;
                        if (arg->flags & FUSE_DONT_MASK)
                                fc->dont_mask = 1;
                        if (arg->flags & FUSE_AUTO_INVAL_DATA)
                                fc->auto_inval_data = 1;
                        else if (arg->flags & FUSE_EXPLICIT_INVAL_DATA)
                                fc->explicit_inval_data = 1;
                        if (arg->flags & FUSE_DO_READDIRPLUS) {
                                fc->do_readdirplus = 1;
                                if (arg->flags & FUSE_READDIRPLUS_AUTO)
                                        fc->readdirplus_auto = 1;
                        }
                        if (arg->flags & FUSE_ASYNC_DIO)
                                fc->async_dio = 1;
                        if (arg->flags & FUSE_WRITEBACK_CACHE)
                                fc->writeback_cache = 1;
                        if (arg->flags & FUSE_PARALLEL_DIROPS)
                                fc->parallel_dirops = 1;
                        if (arg->flags & FUSE_HANDLE_KILLPRIV)
                                fc->handle_killpriv = 1;
                        if (arg->time_gran && arg->time_gran <= 1000000000)
                                fm->sb->s_time_gran = arg->time_gran;
                        if ((arg->flags & FUSE_POSIX_ACL)) {
                                fc->default_permissions = 1;
                                fc->posix_acl = 1;
                                fm->sb->s_xattr = fuse_acl_xattr_handlers;
                        }
                        if (arg->flags & FUSE_CACHE_SYMLINKS)
                                fc->cache_symlinks = 1;
                        if (arg->flags & FUSE_ABORT_ERROR)
                                fc->abort_err = 1;
                        if (arg->flags & FUSE_MAX_PAGES) {
                                fc->max_pages =
                                        min_t(unsigned int, fc->max_pages_limit,
                                        max_t(unsigned int, arg->max_pages, 1));
                        }
                        if (IS_ENABLED(CONFIG_FUSE_DAX) &&
                            arg->flags & FUSE_MAP_ALIGNMENT &&
                            !fuse_dax_check_alignment(fc, arg->map_alignment)) {
                                ok = false;
                        }
                        if (arg->flags & FUSE_HANDLE_KILLPRIV_V2) {
                                fc->handle_killpriv_v2 = 1;
                                fm->sb->s_flags |= SB_NOSEC;
                        }
                        if (arg->flags & FUSE_SETXATTR_EXT)
                                fc->setxattr_ext = 1;
                } else {
                        ra_pages = fc->max_read / PAGE_SIZE;
                        fc->no_lock = 1;
                        fc->no_flock = 1;
                }

                fm->sb->s_bdi->ra_pages =
                                min(fm->sb->s_bdi->ra_pages, ra_pages);
                fc->minor = arg->minor;
                fc->max_write = arg->minor < 5 ? 4096 : arg->max_write;
                fc->max_write = max_t(unsigned, 4096, fc->max_write);
                fc->conn_init = 1;
        }
        kfree(ia);

        if (!ok) {
                fc->conn_init = 0;
                fc->conn_error = 1;
        }

        fuse_set_initialized(fc);
        wake_up_all(&fc->blocked_waitq);
}

void fuse_send_init(struct fuse_mount *fm)
{
        struct fuse_init_args *ia;

        ia = kzalloc(sizeof(*ia), GFP_KERNEL | __GFP_NOFAIL);

        ia->in.major = FUSE_KERNEL_VERSION;
        ia->in.minor = FUSE_KERNEL_MINOR_VERSION;
        ia->in.max_readahead = fm->sb->s_bdi->ra_pages * PAGE_SIZE;
        ia->in.flags |=
                FUSE_ASYNC_READ | FUSE_POSIX_LOCKS | FUSE_ATOMIC_O_TRUNC |
                FUSE_EXPORT_SUPPORT | FUSE_BIG_WRITES | FUSE_DONT_MASK |
                FUSE_SPLICE_WRITE | FUSE_SPLICE_MOVE | FUSE_SPLICE_READ |
                FUSE_FLOCK_LOCKS | FUSE_HAS_IOCTL_DIR | FUSE_AUTO_INVAL_DATA |
                FUSE_DO_READDIRPLUS | FUSE_READDIRPLUS_AUTO | FUSE_ASYNC_DIO |
                FUSE_WRITEBACK_CACHE | FUSE_NO_OPEN_SUPPORT |
                FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL |
                FUSE_ABORT_ERROR | FUSE_MAX_PAGES | FUSE_CACHE_SYMLINKS |
                FUSE_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA |
                FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_EXT;
#ifdef CONFIG_FUSE_DAX
        if (fm->fc->dax)
                ia->in.flags |= FUSE_MAP_ALIGNMENT;
#endif
        if (fm->fc->auto_submounts)
                ia->in.flags |= FUSE_SUBMOUNTS;

        ia->args.opcode = FUSE_INIT;
        ia->args.in_numargs = 1;
        ia->args.in_args[0].size = sizeof(ia->in);
        ia->args.in_args[0].value = &ia->in;
        ia->args.out_numargs = 1;
        /* Variable length argument used for backward compatibility
           with interface version < 7.5.  Rest of init_out is zeroed
           by do_get_request(), so a short reply is not a problem */
        ia->args.out_argvar = true;
        ia->args.out_args[0].size = sizeof(ia->out);
        ia->args.out_args[0].value = &ia->out;
        ia->args.force = true;
        ia->args.nocreds = true;
        ia->args.end = process_init_reply;

        if (fuse_simple_background(fm, &ia->args, GFP_KERNEL) != 0)
                process_init_reply(fm, &ia->args, -ENOTCONN);
}
EXPORT_SYMBOL_GPL(fuse_send_init);

void fuse_free_conn(struct fuse_conn *fc)
{
        WARN_ON(!list_empty(&fc->devices));
        kfree_rcu(fc, rcu);
}
EXPORT_SYMBOL_GPL(fuse_free_conn);

static int fuse_bdi_init(struct fuse_conn *fc, struct super_block *sb)
{
        int err;
        char *suffix = "";

        if (sb->s_bdev) {
                suffix = "-fuseblk";
                /*
                 * sb->s_bdi points to blkdev's bdi however we want to redirect
                 * it to our private bdi...
                 */
                bdi_put(sb->s_bdi);
                sb->s_bdi = &noop_backing_dev_info;
        }
        err = super_setup_bdi_name(sb, "%u:%u%s", MAJOR(fc->dev),
                                   MINOR(fc->dev), suffix);
        if (err)
                return err;

        /* fuse does it's own writeback accounting */
        sb->s_bdi->capabilities &= ~BDI_CAP_WRITEBACK_ACCT;
        sb->s_bdi->capabilities |= BDI_CAP_STRICTLIMIT;

        /*
         * For a single fuse filesystem use max 1% of dirty +
         * writeback threshold.
         *
         * This gives about 1M of write buffer for memory maps on a
         * machine with 1G and 10% dirty_ratio, which should be more
         * than enough.
         *
         * Privileged users can raise it by writing to
         *
         *    /sys/class/bdi/<bdi>/max_ratio
         */
        bdi_set_max_ratio(sb->s_bdi, 1);

        return 0;
}

struct fuse_dev *fuse_dev_alloc(void)
{
        struct fuse_dev *fud;
        struct list_head *pq;

        fud = kzalloc(sizeof(struct fuse_dev), GFP_KERNEL);
        if (!fud)
                return NULL;

        pq = kcalloc(FUSE_PQ_HASH_SIZE, sizeof(struct list_head), GFP_KERNEL);
        if (!pq) {
                kfree(fud);
                return NULL;
        }

        fud->pq.processing = pq;
        fuse_pqueue_init(&fud->pq);

        return fud;
}
EXPORT_SYMBOL_GPL(fuse_dev_alloc);

void fuse_dev_install(struct fuse_dev *fud, struct fuse_conn *fc)
{
        fud->fc = fuse_conn_get(fc);
        spin_lock(&fc->lock);
        list_add_tail(&fud->entry, &fc->devices);
        spin_unlock(&fc->lock);
}
EXPORT_SYMBOL_GPL(fuse_dev_install);

struct fuse_dev *fuse_dev_alloc_install(struct fuse_conn *fc)
{
        struct fuse_dev *fud;

        fud = fuse_dev_alloc();
        if (!fud)
                return NULL;

        fuse_dev_install(fud, fc);
        return fud;
}
EXPORT_SYMBOL_GPL(fuse_dev_alloc_install);

void fuse_dev_free(struct fuse_dev *fud)
{
        struct fuse_conn *fc = fud->fc;

        if (fc) {
                spin_lock(&fc->lock);
                list_del(&fud->entry);
                spin_unlock(&fc->lock);

                fuse_conn_put(fc);
        }
        kfree(fud->pq.processing);
        kfree(fud);
}
EXPORT_SYMBOL_GPL(fuse_dev_free);

static void fuse_fill_attr_from_inode(struct fuse_attr *attr,
                                      const struct fuse_inode *fi)
{
        *attr = (struct fuse_attr){
                .ino            = fi->inode.i_ino,
                .size           = fi->inode.i_size,
                .blocks         = fi->inode.i_blocks,
                .atime          = fi->inode.i_atime.tv_sec,
                .mtime          = fi->inode.i_mtime.tv_sec,
                .ctime          = fi->inode.i_ctime.tv_sec,
                .atimensec      = fi->inode.i_atime.tv_nsec,
                .mtimensec      = fi->inode.i_mtime.tv_nsec,
                .ctimensec      = fi->inode.i_ctime.tv_nsec,
                .mode           = fi->inode.i_mode,
                .nlink          = fi->inode.i_nlink,
                .uid            = fi->inode.i_uid.val,
                .gid            = fi->inode.i_gid.val,
                .rdev           = fi->inode.i_rdev,
                .blksize        = 1u << fi->inode.i_blkbits,
        };
}

static void fuse_sb_defaults(struct super_block *sb)
{
        sb->s_magic = FUSE_SUPER_MAGIC;
        sb->s_op = &fuse_super_operations;
        sb->s_xattr = fuse_xattr_handlers;
        sb->s_maxbytes = MAX_LFS_FILESIZE;
        sb->s_time_gran = 1;
        sb->s_export_op = &fuse_export_operations;
        sb->s_iflags |= SB_I_IMA_UNVERIFIABLE_SIGNATURE;
        if (sb->s_user_ns != &init_user_ns)
                sb->s_iflags |= SB_I_UNTRUSTED_MOUNTER;
        sb->s_flags &= ~(SB_NOSEC | SB_I_VERSION);

        /*
         * If we are not in the initial user namespace posix
         * acls must be translated.
         */
        if (sb->s_user_ns != &init_user_ns)
                sb->s_xattr = fuse_no_acl_xattr_handlers;
}

static int fuse_fill_super_submount(struct super_block *sb,
                                    struct fuse_inode *parent_fi)
{
        struct fuse_mount *fm = get_fuse_mount_super(sb);
        struct super_block *parent_sb = parent_fi->inode.i_sb;
        struct fuse_attr root_attr;
        struct inode *root;

        fuse_sb_defaults(sb);
        fm->sb = sb;

        WARN_ON(sb->s_bdi != &noop_backing_dev_info);
        sb->s_bdi = bdi_get(parent_sb->s_bdi);

        sb->s_xattr = parent_sb->s_xattr;
        sb->s_time_gran = parent_sb->s_time_gran;
        sb->s_blocksize = parent_sb->s_blocksize;
        sb->s_blocksize_bits = parent_sb->s_blocksize_bits;
        sb->s_subtype = kstrdup(parent_sb->s_subtype, GFP_KERNEL);
        if (parent_sb->s_subtype && !sb->s_subtype)
                return -ENOMEM;

        fuse_fill_attr_from_inode(&root_attr, parent_fi);
        root = fuse_iget(sb, parent_fi->nodeid, 0, &root_attr, 0, 0);
        /*
         * This inode is just a duplicate, so it is not looked up and
         * its nlookup should not be incremented.  fuse_iget() does
         * that, though, so undo it here.
         */
        get_fuse_inode(root)->nlookup--;
        sb->s_d_op = &fuse_dentry_operations;
        sb->s_root = d_make_root(root);
        if (!sb->s_root)
                return -ENOMEM;

        return 0;
}

/* Filesystem context private data holds the FUSE inode of the mount point */
static int fuse_get_tree_submount(struct fs_context *fsc)
{
        struct fuse_mount *fm;
        struct fuse_inode *mp_fi = fsc->fs_private;
        struct fuse_conn *fc = get_fuse_conn(&mp_fi->inode);
        struct super_block *sb;
        int err;

        fm = kzalloc(sizeof(struct fuse_mount), GFP_KERNEL);
        if (!fm)
                return -ENOMEM;

        fm->fc = fuse_conn_get(fc);
        fsc->s_fs_info = fm;
        sb = sget_fc(fsc, NULL, set_anon_super_fc);
        if (fsc->s_fs_info)
                fuse_mount_destroy(fm);
        if (IS_ERR(sb))
                return PTR_ERR(sb);

        /* Initialize superblock, making @mp_fi its root */
        err = fuse_fill_super_submount(sb, mp_fi);
        if (err) {
                deactivate_locked_super(sb);
                return err;
        }

        down_write(&fc->killsb);
        list_add_tail(&fm->fc_entry, &fc->mounts);
        up_write(&fc->killsb);

        sb->s_flags |= SB_ACTIVE;
        fsc->root = dget(sb->s_root);

        return 0;
}

static const struct fs_context_operations fuse_context_submount_ops = {
        .get_tree       = fuse_get_tree_submount,
};

int fuse_init_fs_context_submount(struct fs_context *fsc)
{
        fsc->ops = &fuse_context_submount_ops;
        return 0;
}
EXPORT_SYMBOL_GPL(fuse_init_fs_context_submount);

int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
{
        struct fuse_dev *fud = NULL;
        struct fuse_mount *fm = get_fuse_mount_super(sb);
        struct fuse_conn *fc = fm->fc;
        struct inode *root;
        struct dentry *root_dentry;
        int err;

        err = -EINVAL;
        if (sb->s_flags & SB_MANDLOCK)
                goto err;

        rcu_assign_pointer(fc->curr_bucket, fuse_sync_bucket_alloc());
        fuse_sb_defaults(sb);

        if (ctx->is_bdev) {
#ifdef CONFIG_BLOCK
                err = -EINVAL;
                if (!sb_set_blocksize(sb, ctx->blksize))
                        goto err;
#endif
        } else {
                sb->s_blocksize = PAGE_SIZE;
                sb->s_blocksize_bits = PAGE_SHIFT;
        }

        sb->s_subtype = ctx->subtype;
        ctx->subtype = NULL;
        if (IS_ENABLED(CONFIG_FUSE_DAX)) {
                err = fuse_dax_conn_alloc(fc, ctx->dax_dev);
                if (err)
                        goto err;
        }

        if (ctx->fudptr) {
                err = -ENOMEM;
                fud = fuse_dev_alloc_install(fc);
                if (!fud)
                        goto err_free_dax;
        }

        fc->dev = sb->s_dev;
        fm->sb = sb;
        err = fuse_bdi_init(fc, sb);
        if (err)
                goto err_dev_free;

        /* Handle umasking inside the fuse code */
        if (sb->s_flags & SB_POSIXACL)
                fc->dont_mask = 1;
        sb->s_flags |= SB_POSIXACL;

        fc->default_permissions = ctx->default_permissions;
        fc->allow_other = ctx->allow_other;
        fc->user_id = ctx->user_id;
        fc->group_id = ctx->group_id;
        fc->legacy_opts_show = ctx->legacy_opts_show;
        fc->max_read = max_t(unsigned int, 4096, ctx->max_read);
        fc->destroy = ctx->destroy;
        fc->no_control = ctx->no_control;
        fc->no_force_umount = ctx->no_force_umount;

        err = -ENOMEM;
        root = fuse_get_root_inode(sb, ctx->rootmode);
        sb->s_d_op = &fuse_root_dentry_operations;
        root_dentry = d_make_root(root);
        if (!root_dentry)
                goto err_dev_free;
        /* Root dentry doesn't have .d_revalidate */
        sb->s_d_op = &fuse_dentry_operations;

        mutex_lock(&fuse_mutex);
        err = -EINVAL;
        if (ctx->fudptr && *ctx->fudptr)
                goto err_unlock;

        err = fuse_ctl_add_conn(fc);
        if (err)
                goto err_unlock;

        list_add_tail(&fc->entry, &fuse_conn_list);
        sb->s_root = root_dentry;
        if (ctx->fudptr)
                *ctx->fudptr = fud;
        mutex_unlock(&fuse_mutex);
        return 0;

 err_unlock:
        mutex_unlock(&fuse_mutex);
        dput(root_dentry);
 err_dev_free:
        if (fud)
                fuse_dev_free(fud);
 err_free_dax:
        if (IS_ENABLED(CONFIG_FUSE_DAX))
                fuse_dax_conn_free(fc);
 err:
        return err;
}
EXPORT_SYMBOL_GPL(fuse_fill_super_common);

static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
{
        struct fuse_fs_context *ctx = fsc->fs_private;
        int err;

        if (!ctx->file || !ctx->rootmode_present ||
            !ctx->user_id_present || !ctx->group_id_present)
                return -EINVAL;

        /*
         * Require mount to happen from the same user namespace which
         * opened /dev/fuse to prevent potential attacks.
         */
        if ((ctx->file->f_op != &fuse_dev_operations) ||
            (ctx->file->f_cred->user_ns != sb->s_user_ns))
                return -EINVAL;
        ctx->fudptr = &ctx->file->private_data;

        err = fuse_fill_super_common(sb, ctx);
        if (err)
                return err;
        /* file->private_data shall be visible on all CPUs after this */
        smp_mb();
        fuse_send_init(get_fuse_mount_super(sb));
        return 0;
}

/*
 * This is the path where user supplied an already initialized fuse dev.  In
 * this case never create a new super if the old one is gone.
 */
static int fuse_set_no_super(struct super_block *sb, struct fs_context *fsc)
{
        return -ENOTCONN;
}

static int fuse_test_super(struct super_block *sb, struct fs_context *fsc)
{

        return fsc->sget_key == get_fuse_conn_super(sb);
}

static int fuse_get_tree(struct fs_context *fsc)
{
        struct fuse_fs_context *ctx = fsc->fs_private;
        struct fuse_dev *fud;
        struct fuse_conn *fc;
        struct fuse_mount *fm;
        struct super_block *sb;
        int err;

        fc = kmalloc(sizeof(*fc), GFP_KERNEL);
        if (!fc)
                return -ENOMEM;

        fm = kzalloc(sizeof(*fm), GFP_KERNEL);
        if (!fm) {
                kfree(fc);
                return -ENOMEM;
        }

        fuse_conn_init(fc, fm, fsc->user_ns, &fuse_dev_fiq_ops, NULL);
        fc->release = fuse_free_conn;

        fsc->s_fs_info = fm;

        if (ctx->fd_present)
                ctx->file = fget(ctx->fd);

        if (IS_ENABLED(CONFIG_BLOCK) && ctx->is_bdev) {
                err = get_tree_bdev(fsc, fuse_fill_super);
                goto out;
        }
        /*
         * While block dev mount can be initialized with a dummy device fd
         * (found by device name), normal fuse mounts can't
         */
        err = -EINVAL;
        if (!ctx->file)
                goto out;

        /*
         * Allow creating a fuse mount with an already initialized fuse
         * connection
         */
        fud = READ_ONCE(ctx->file->private_data);
        if (ctx->file->f_op == &fuse_dev_operations && fud) {
                fsc->sget_key = fud->fc;
                sb = sget_fc(fsc, fuse_test_super, fuse_set_no_super);
                err = PTR_ERR_OR_ZERO(sb);
                if (!IS_ERR(sb))
                        fsc->root = dget(sb->s_root);
        } else {
                err = get_tree_nodev(fsc, fuse_fill_super);
        }
out:
        if (fsc->s_fs_info)
                fuse_mount_destroy(fm);
        if (ctx->file)
                fput(ctx->file);
        return err;
}

static const struct fs_context_operations fuse_context_ops = {
        .free           = fuse_free_fsc,
        .parse_param    = fuse_parse_param,
        .reconfigure    = fuse_reconfigure,
        .get_tree       = fuse_get_tree,
};

/*
 * Set up the filesystem mount context.
 */
static int fuse_init_fs_context(struct fs_context *fsc)
{
        struct fuse_fs_context *ctx;

        ctx = kzalloc(sizeof(struct fuse_fs_context), GFP_KERNEL);
        if (!ctx)
                return -ENOMEM;

        ctx->max_read = ~0;
        ctx->blksize = FUSE_DEFAULT_BLKSIZE;
        ctx->legacy_opts_show = true;

#ifdef CONFIG_BLOCK
        if (fsc->fs_type == &fuseblk_fs_type) {
                ctx->is_bdev = true;
                ctx->destroy = true;
        }
#endif

        fsc->fs_private = ctx;
        fsc->ops = &fuse_context_ops;
        return 0;
}

bool fuse_mount_remove(struct fuse_mount *fm)
{
        struct fuse_conn *fc = fm->fc;
        bool last = false;

        down_write(&fc->killsb);
        list_del_init(&fm->fc_entry);
        if (list_empty(&fc->mounts))
                last = true;
        up_write(&fc->killsb);

        return last;
}
EXPORT_SYMBOL_GPL(fuse_mount_remove);

void fuse_conn_destroy(struct fuse_mount *fm)
{
        struct fuse_conn *fc = fm->fc;

        if (fc->destroy)
                fuse_send_destroy(fm);

        fuse_abort_conn(fc);
        fuse_wait_aborted(fc);

        if (!list_empty(&fc->entry)) {
                mutex_lock(&fuse_mutex);
                list_del(&fc->entry);
                fuse_ctl_remove_conn(fc);
                mutex_unlock(&fuse_mutex);
        }
}
EXPORT_SYMBOL_GPL(fuse_conn_destroy);

static void fuse_sb_destroy(struct super_block *sb)
{
        struct fuse_mount *fm = get_fuse_mount_super(sb);
        bool last;

        if (sb->s_root) {
                last = fuse_mount_remove(fm);
                if (last)
                        fuse_conn_destroy(fm);
        }
}

void fuse_mount_destroy(struct fuse_mount *fm)
{
        fuse_conn_put(fm->fc);
        kfree(fm);
}
EXPORT_SYMBOL(fuse_mount_destroy);

static void fuse_kill_sb_anon(struct super_block *sb)
{
        fuse_sb_destroy(sb);
        kill_anon_super(sb);
        fuse_mount_destroy(get_fuse_mount_super(sb));
}

static struct file_system_type fuse_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "fuse",
        .fs_flags       = FS_HAS_SUBTYPE | FS_USERNS_MOUNT,
        .init_fs_context = fuse_init_fs_context,
        .parameters     = fuse_fs_parameters,
        .kill_sb        = fuse_kill_sb_anon,
};
MODULE_ALIAS_FS("fuse");

#ifdef CONFIG_BLOCK
static void fuse_kill_sb_blk(struct super_block *sb)
{
        fuse_sb_destroy(sb);
        kill_block_super(sb);
        fuse_mount_destroy(get_fuse_mount_super(sb));
}

static struct file_system_type fuseblk_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "fuseblk",
        .init_fs_context = fuse_init_fs_context,
        .parameters     = fuse_fs_parameters,
        .kill_sb        = fuse_kill_sb_blk,
        .fs_flags       = FS_REQUIRES_DEV | FS_HAS_SUBTYPE,
};
MODULE_ALIAS_FS("fuseblk");

static inline int register_fuseblk(void)
{
        return register_filesystem(&fuseblk_fs_type);
}

static inline void unregister_fuseblk(void)
{
        unregister_filesystem(&fuseblk_fs_type);
}
#else
static inline int register_fuseblk(void)
{
        return 0;
}

static inline void unregister_fuseblk(void)
{
}
#endif

static void fuse_inode_init_once(void *foo)
{
        struct inode *inode = foo;

        inode_init_once(inode);
}

static int __init fuse_fs_init(void)
{
        int err;

        fuse_inode_cachep = kmem_cache_create("fuse_inode",
                        sizeof(struct fuse_inode), 0,
                        SLAB_HWCACHE_ALIGN|SLAB_ACCOUNT|SLAB_RECLAIM_ACCOUNT,
                        fuse_inode_init_once);
        err = -ENOMEM;
        if (!fuse_inode_cachep)
                goto out;

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

        err = register_filesystem(&fuse_fs_type);
        if (err)
                goto out3;

        return 0;

 out3:
        unregister_fuseblk();
 out2:
        kmem_cache_destroy(fuse_inode_cachep);
 out:
        return err;
}

static void fuse_fs_cleanup(void)
{
        unregister_filesystem(&fuse_fs_type);
        unregister_fuseblk();

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

static struct kobject *fuse_kobj;

static int fuse_sysfs_init(void)
{
        int err;

        fuse_kobj = kobject_create_and_add("fuse", fs_kobj);
        if (!fuse_kobj) {
                err = -ENOMEM;
                goto out_err;
        }

        err = sysfs_create_mount_point(fuse_kobj, "connections");
        if (err)
                goto out_fuse_unregister;

        return 0;

 out_fuse_unregister:
        kobject_put(fuse_kobj);
 out_err:
        return err;
}

static void fuse_sysfs_cleanup(void)
{
        sysfs_remove_mount_point(fuse_kobj, "connections");
        kobject_put(fuse_kobj);
}

static int __init fuse_init(void)
{
        int res;

        pr_info("init (API version %i.%i)\n",
                FUSE_KERNEL_VERSION, FUSE_KERNEL_MINOR_VERSION);

        INIT_LIST_HEAD(&fuse_conn_list);
        res = fuse_fs_init();
        if (res)
                goto err;

        res = fuse_dev_init();
        if (res)
                goto err_fs_cleanup;

        res = fuse_sysfs_init();
        if (res)
                goto err_dev_cleanup;

        res = fuse_ctl_init();
        if (res)
                goto err_sysfs_cleanup;

        sanitize_global_limit(&max_user_bgreq);
        sanitize_global_limit(&max_user_congthresh);

        return 0;

 err_sysfs_cleanup:
        fuse_sysfs_cleanup();
 err_dev_cleanup:
        fuse_dev_cleanup();
 err_fs_cleanup:
        fuse_fs_cleanup();
 err:
        return res;
}

static void __exit fuse_exit(void)
{
        pr_debug("exit\n");

        fuse_ctl_cleanup();
        fuse_sysfs_cleanup();
        fuse_fs_cleanup();
        fuse_dev_cleanup();
}

module_init(fuse_init);
module_exit(fuse_exit);