SSL libfs.c Sprache: C

// SPDX-License-Identifier: GPL-2.0-only
/*
* fs/libfs.c
* Library for filesystems writers.
*/

#include <linux/blkdev.h>
#include <linux/export.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/mount.h>
#include <linux/vfs.h>
#include <linux/quotaops.h>
#include <linux/mutex.h>
#include <linux/namei.h>
#include <linux/exportfs.h>
#include <linux/iversion.h>
#include <linux/writeback.h>
#include <linux/buffer_head.h> /* sync_mapping_buffers */
#include <linux/fs_context.h>
#include <linux/pseudo_fs.h>
#include <linux/fsnotify.h>
#include <linux/unicode.h>
#include <linux/fscrypt.h>
#include <linux/pidfs.h>

#include <linux/uaccess.h>

#include "internal.h"

int simple_getattr(struct mnt_idmap *idmap, const struct path *path,
     struct kstat *stat, u32 request_mask,
     unsigned int query_flags)
{
struct inode *inode = d_inode(path->dentry);
generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
stat->blocks = inode->i_mapping->nrpages << (PAGE_SHIFT - 9);
return 0;
}
EXPORT_SYMBOL(simple_getattr);

int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
{
u64 id = huge_encode_dev(dentry->d_sb->s_dev);

buf->f_fsid = u64_to_fsid(id);
buf->f_type = dentry->d_sb->s_magic;
buf->f_bsize = PAGE_SIZE;
buf->f_namelen = NAME_MAX;
return 0;
}
EXPORT_SYMBOL(simple_statfs);

/*
* Retaining negative dentries for an in-memory filesystem just wastes
* memory and lookup time: arrange for them to be deleted immediately.
*/
int always_delete_dentry(const struct dentry *dentry)
{
return 1;
}
EXPORT_SYMBOL(always_delete_dentry);

/*
* Lookup the data. This is trivial - if the dentry didn't already
* exist, we know it is negative.  Set d_op to delete negative dentries.
*/
struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
{
if (dentry->d_name.len > NAME_MAX)
  return ERR_PTR(-ENAMETOOLONG);
if (!dentry->d_op && !(dentry->d_flags & DCACHE_DONTCACHE)) {
  spin_lock(&dentry->d_lock);
  dentry->d_flags |= DCACHE_DONTCACHE;
  spin_unlock(&dentry->d_lock);
}
if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir))
  return NULL;

d_add(dentry, NULL);
return NULL;
}
EXPORT_SYMBOL(simple_lookup);

int dcache_dir_open(struct inode *inode, struct file *file)
{
file->private_data = d_alloc_cursor(file->f_path.dentry);

return file->private_data ? 0 : -ENOMEM;
}
EXPORT_SYMBOL(dcache_dir_open);

int dcache_dir_close(struct inode *inode, struct file *file)
{
dput(file->private_data);
return 0;
}
EXPORT_SYMBOL(dcache_dir_close);

/* parent is locked at least shared */
/*
* Returns an element of siblings' list.
* We are looking for <count>th positive after <p>; if
* found, dentry is grabbed and returned to caller.
* If no such element exists, NULL is returned.
*/
static struct dentry *scan_positives(struct dentry *cursor,
     struct hlist_node **p,
     loff_t count,
     struct dentry *last)
{
struct dentry *dentry = cursor->d_parent, *found = NULL;

spin_lock(&dentry->d_lock);
while (*p) {
  struct dentry *d = hlist_entry(*p, struct dentry, d_sib);
  p = &d->d_sib.next;
  // we must at least skip cursors, to avoid livelocks
  if (d->d_flags & DCACHE_DENTRY_CURSOR)
   continue;
  if (simple_positive(d) && !--count) {
   spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
   if (simple_positive(d))
    found = dget_dlock(d);
   spin_unlock(&d->d_lock);
   if (likely(found))
    break;
   count = 1;
  }
  if (need_resched()) {
   if (!hlist_unhashed(&cursor->d_sib))
    __hlist_del(&cursor->d_sib);
   hlist_add_behind(&cursor->d_sib, &d->d_sib);
   p = &cursor->d_sib.next;
   spin_unlock(&dentry->d_lock);
   cond_resched();
   spin_lock(&dentry->d_lock);
  }
}
spin_unlock(&dentry->d_lock);
dput(last);
return found;
}

loff_t dcache_dir_lseek(struct file *file, loff_t offset, int whence)
{
struct dentry *dentry = file->f_path.dentry;
switch (whence) {
  case 1:
   offset += file->f_pos;
   fallthrough;
  case 0:
   if (offset >= 0)
    break;
   fallthrough;
  default:
   return -EINVAL;
}
if (offset != file->f_pos) {
  struct dentry *cursor = file->private_data;
  struct dentry *to = NULL;

  inode_lock_shared(dentry->d_inode);

  if (offset > 2)
   to = scan_positives(cursor, &dentry->d_children.first,
         offset - 2, NULL);
  spin_lock(&dentry->d_lock);
  hlist_del_init(&cursor->d_sib);
  if (to)
   hlist_add_behind(&cursor->d_sib, &to->d_sib);
  spin_unlock(&dentry->d_lock);
  dput(to);

  file->f_pos = offset;

  inode_unlock_shared(dentry->d_inode);
}
return offset;
}
EXPORT_SYMBOL(dcache_dir_lseek);

/*
* Directory is locked and all positive dentries in it are safe, since
* for ramfs-type trees they can't go away without unlink() or rmdir(),
* both impossible due to the lock on directory.
*/

int dcache_readdir(struct file *file, struct dir_context *ctx)
{
struct dentry *dentry = file->f_path.dentry;
struct dentry *cursor = file->private_data;
struct dentry *next = NULL;
struct hlist_node **p;

if (!dir_emit_dots(file, ctx))
  return 0;

if (ctx->pos == 2)
  p = &dentry->d_children.first;
else
  p = &cursor->d_sib.next;

while ((next = scan_positives(cursor, p, 1, next)) != NULL) {
  if (!dir_emit(ctx, next->d_name.name, next->d_name.len,
         d_inode(next)->i_ino,
         fs_umode_to_dtype(d_inode(next)->i_mode)))
   break;
  ctx->pos++;
  p = &next->d_sib.next;
}
spin_lock(&dentry->d_lock);
hlist_del_init(&cursor->d_sib);
if (next)
  hlist_add_before(&cursor->d_sib, &next->d_sib);
spin_unlock(&dentry->d_lock);
dput(next);

return 0;
}
EXPORT_SYMBOL(dcache_readdir);

ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
{
return -EISDIR;
}
EXPORT_SYMBOL(generic_read_dir);

const struct file_operations simple_dir_operations = {
.open  = dcache_dir_open,
.release = dcache_dir_close,
.llseek  = dcache_dir_lseek,
.read  = generic_read_dir,
.iterate_shared = dcache_readdir,
.fsync  = noop_fsync,
};
EXPORT_SYMBOL(simple_dir_operations);

const struct inode_operations simple_dir_inode_operations = {
.lookup  = simple_lookup,
};
EXPORT_SYMBOL(simple_dir_inode_operations);

/* simple_offset_add() never assigns these to a dentry */
enum {
DIR_OFFSET_FIRST = 2,  /* Find first real entry */
DIR_OFFSET_EOD  = S32_MAX,
};

/* simple_offset_add() allocation range */
enum {
DIR_OFFSET_MIN  = DIR_OFFSET_FIRST + 1,
DIR_OFFSET_MAX  = DIR_OFFSET_EOD - 1,
};

static void offset_set(struct dentry *dentry, long offset)
{
dentry->d_fsdata = (void *)offset;
}

static long dentry2offset(struct dentry *dentry)
{
return (long)dentry->d_fsdata;
}

static struct lock_class_key simple_offset_lock_class;

/**
* simple_offset_init - initialize an offset_ctx
* @octx: directory offset map to be initialized
*
*/
void simple_offset_init(struct offset_ctx *octx)
{
mt_init_flags(&octx->mt, MT_FLAGS_ALLOC_RANGE);
lockdep_set_class(&octx->mt.ma_lock, &simple_offset_lock_class);
octx->next_offset = DIR_OFFSET_MIN;
}

/**
* simple_offset_add - Add an entry to a directory's offset map
* @octx: directory offset ctx to be updated
* @dentry: new dentry being added
*
* Returns zero on success. @octx and the dentry's offset are updated.
* Otherwise, a negative errno value is returned.
*/
int simple_offset_add(struct offset_ctx *octx, struct dentry *dentry)
{
unsigned long offset;
int ret;

if (dentry2offset(dentry) != 0)
  return -EBUSY;

ret = mtree_alloc_cyclic(&octx->mt, &offset, dentry, DIR_OFFSET_MIN,
     DIR_OFFSET_MAX, &octx->next_offset,
     GFP_KERNEL);
if (unlikely(ret < 0))
  return ret == -EBUSY ? -ENOSPC : ret;

offset_set(dentry, offset);
return 0;
}

static int simple_offset_replace(struct offset_ctx *octx, struct dentry *dentry,
     long offset)
{
int ret;

ret = mtree_store(&octx->mt, offset, dentry, GFP_KERNEL);
if (ret)
  return ret;
offset_set(dentry, offset);
return 0;
}

/**
* simple_offset_remove - Remove an entry to a directory's offset map
* @octx: directory offset ctx to be updated
* @dentry: dentry being removed
*
*/
void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry)
{
long offset;

offset = dentry2offset(dentry);
if (offset == 0)
  return;

mtree_erase(&octx->mt, offset);
offset_set(dentry, 0);
}

/**
* simple_offset_rename - handle directory offsets for rename
* @old_dir: parent directory of source entry
* @old_dentry: dentry of source entry
* @new_dir: parent_directory of destination entry
* @new_dentry: dentry of destination
*
* Caller provides appropriate serialization.
*
* User space expects the directory offset value of the replaced
* (new) directory entry to be unchanged after a rename.
*
* Returns zero on success, a negative errno value on failure.
*/
int simple_offset_rename(struct inode *old_dir, struct dentry *old_dentry,
    struct inode *new_dir, struct dentry *new_dentry)
{
struct offset_ctx *old_ctx = old_dir->i_op->get_offset_ctx(old_dir);
struct offset_ctx *new_ctx = new_dir->i_op->get_offset_ctx(new_dir);
long new_offset = dentry2offset(new_dentry);

simple_offset_remove(old_ctx, old_dentry);

if (new_offset) {
  offset_set(new_dentry, 0);
  return simple_offset_replace(new_ctx, old_dentry, new_offset);
}
return simple_offset_add(new_ctx, old_dentry);
}

/**
* simple_offset_rename_exchange - exchange rename with directory offsets
* @old_dir: parent of dentry being moved
* @old_dentry: dentry being moved
* @new_dir: destination parent
* @new_dentry: destination dentry
*
* This API preserves the directory offset values. Caller provides
* appropriate serialization.
*
* Returns zero on success. Otherwise a negative errno is returned and the
* rename is rolled back.
*/
int simple_offset_rename_exchange(struct inode *old_dir,
      struct dentry *old_dentry,
      struct inode *new_dir,
      struct dentry *new_dentry)
{
struct offset_ctx *old_ctx = old_dir->i_op->get_offset_ctx(old_dir);
struct offset_ctx *new_ctx = new_dir->i_op->get_offset_ctx(new_dir);
long old_index = dentry2offset(old_dentry);
long new_index = dentry2offset(new_dentry);
int ret;

simple_offset_remove(old_ctx, old_dentry);
simple_offset_remove(new_ctx, new_dentry);

ret = simple_offset_replace(new_ctx, old_dentry, new_index);
if (ret)
  goto out_restore;

ret = simple_offset_replace(old_ctx, new_dentry, old_index);
if (ret) {
  simple_offset_remove(new_ctx, old_dentry);
  goto out_restore;
}

ret = simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
if (ret) {
  simple_offset_remove(new_ctx, old_dentry);
  simple_offset_remove(old_ctx, new_dentry);
  goto out_restore;
}
return 0;

out_restore:
(void)simple_offset_replace(old_ctx, old_dentry, old_index);
(void)simple_offset_replace(new_ctx, new_dentry, new_index);
return ret;
}

/**
* simple_offset_destroy - Release offset map
* @octx: directory offset ctx that is about to be destroyed
*
* During fs teardown (eg. umount), a directory's offset map might still
* contain entries. xa_destroy() cleans out anything that remains.
*/
void simple_offset_destroy(struct offset_ctx *octx)
{
mtree_destroy(&octx->mt);
}

/**
* offset_dir_llseek - Advance the read position of a directory descriptor
* @file: an open directory whose position is to be updated
* @offset: a byte offset
* @whence: enumerator describing the starting position for this update
*
* SEEK_END, SEEK_DATA, and SEEK_HOLE are not supported for directories.
*
* Returns the updated read position if successful; otherwise a
* negative errno is returned and the read position remains unchanged.
*/
static loff_t offset_dir_llseek(struct file *file, loff_t offset, int whence)
{
switch (whence) {
case SEEK_CUR:
  offset += file->f_pos;
  fallthrough;
case SEEK_SET:
  if (offset >= 0)
   break;
  fallthrough;
default:
  return -EINVAL;
}

return vfs_setpos(file, offset, LONG_MAX);
}

static struct dentry *find_positive_dentry(struct dentry *parent,
        struct dentry *dentry,
        bool next)
{
struct dentry *found = NULL;

spin_lock(&parent->d_lock);
if (next)
  dentry = d_next_sibling(dentry);
else if (!dentry)
  dentry = d_first_child(parent);
hlist_for_each_entry_from(dentry, d_sib) {
  if (!simple_positive(dentry))
   continue;
  spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
  if (simple_positive(dentry))
   found = dget_dlock(dentry);
  spin_unlock(&dentry->d_lock);
  if (likely(found))
   break;
}
spin_unlock(&parent->d_lock);
return found;
}

static noinline_for_stack struct dentry *
offset_dir_lookup(struct dentry *parent, loff_t offset)
{
struct inode *inode = d_inode(parent);
struct offset_ctx *octx = inode->i_op->get_offset_ctx(inode);
struct dentry *child, *found = NULL;

MA_STATE(mas, &octx->mt, offset, offset);

if (offset == DIR_OFFSET_FIRST)
  found = find_positive_dentry(parent, NULL, false);
else {
  rcu_read_lock();
  child = mas_find_rev(&mas, DIR_OFFSET_MIN);
  found = find_positive_dentry(parent, child, false);
  rcu_read_unlock();
}
return found;
}

static bool offset_dir_emit(struct dir_context *ctx, struct dentry *dentry)
{
struct inode *inode = d_inode(dentry);

return dir_emit(ctx, dentry->d_name.name, dentry->d_name.len,
   inode->i_ino, fs_umode_to_dtype(inode->i_mode));
}

static void offset_iterate_dir(struct file *file, struct dir_context *ctx)
{
struct dentry *dir = file->f_path.dentry;
struct dentry *dentry;

dentry = offset_dir_lookup(dir, ctx->pos);
if (!dentry)
  goto out_eod;
while (true) {
  struct dentry *next;

  ctx->pos = dentry2offset(dentry);
  if (!offset_dir_emit(ctx, dentry))
   break;

  next = find_positive_dentry(dir, dentry, true);
  dput(dentry);

  if (!next)
   goto out_eod;
  dentry = next;
}
dput(dentry);
return;

out_eod:
ctx->pos = DIR_OFFSET_EOD;
}

/**
* offset_readdir - Emit entries starting at offset @ctx->pos
* @file: an open directory to iterate over
* @ctx: directory iteration context
*
* Caller must hold @file's i_rwsem to prevent insertion or removal of
* entries during this call.
*
* On entry, @ctx->pos contains an offset that represents the first entry
* to be read from the directory.
*
* The operation continues until there are no more entries to read, or
* until the ctx->actor indicates there is no more space in the caller's
* output buffer.
*
* On return, @ctx->pos contains an offset that will read the next entry
* in this directory when offset_readdir() is called again with @ctx.
* Caller places this value in the d_off field of the last entry in the
* user's buffer.
*
* Return values:
*   %0 - Complete
*/
static int offset_readdir(struct file *file, struct dir_context *ctx)
{
struct dentry *dir = file->f_path.dentry;

lockdep_assert_held(&d_inode(dir)->i_rwsem);

if (!dir_emit_dots(file, ctx))
  return 0;
if (ctx->pos != DIR_OFFSET_EOD)
  offset_iterate_dir(file, ctx);
return 0;
}

const struct file_operations simple_offset_dir_operations = {
.llseek  = offset_dir_llseek,
.iterate_shared = offset_readdir,
.read  = generic_read_dir,
.fsync  = noop_fsync,
};

struct dentry *find_next_child(struct dentry *parent, struct dentry *prev)
{
struct dentry *child = NULL, *d;

spin_lock(&parent->d_lock);
d = prev ? d_next_sibling(prev) : d_first_child(parent);
hlist_for_each_entry_from(d, d_sib) {
  if (simple_positive(d)) {
   spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
   if (simple_positive(d))
    child = dget_dlock(d);
   spin_unlock(&d->d_lock);
   if (likely(child))
    break;
  }
}
spin_unlock(&parent->d_lock);
dput(prev);
return child;
}
EXPORT_SYMBOL(find_next_child);

static void __simple_recursive_removal(struct dentry *dentry,
                              void (*callback)(struct dentry *),
         bool locked)
{
struct dentry *this = dget(dentry);
while (true) {
  struct dentry *victim = NULL, *child;
  struct inode *inode = this->d_inode;

  inode_lock_nested(inode, I_MUTEX_CHILD);
  if (d_is_dir(this))
   inode->i_flags |= S_DEAD;
  while ((child = find_next_child(this, victim)) == NULL) {
   // kill and ascend
   // update metadata while it's still locked
   inode_set_ctime_current(inode);
   clear_nlink(inode);
   inode_unlock(inode);
   victim = this;
   this = this->d_parent;
   inode = this->d_inode;
   if (!locked || victim != dentry)
    inode_lock_nested(inode, I_MUTEX_CHILD);
   if (simple_positive(victim)) {
    d_invalidate(victim); // avoid lost mounts
    if (callback)
     callback(victim);
    fsnotify_delete(inode, d_inode(victim), victim);
    dput(victim);  // unpin it
   }
   if (victim == dentry) {
    inode_set_mtime_to_ts(inode,
            inode_set_ctime_current(inode));
    if (d_is_dir(dentry))
     drop_nlink(inode);
    if (!locked)
     inode_unlock(inode);
    dput(dentry);
    return;
   }
  }
  inode_unlock(inode);
  this = child;
}
}

void simple_recursive_removal(struct dentry *dentry,
                              void (*callback)(struct dentry *))
{
return __simple_recursive_removal(dentry, callback, false);
}
EXPORT_SYMBOL(simple_recursive_removal);

/* caller holds parent directory with I_MUTEX_PARENT */
void locked_recursive_removal(struct dentry *dentry,
                              void (*callback)(struct dentry *))
{
return __simple_recursive_removal(dentry, callback, true);
}
EXPORT_SYMBOL(locked_recursive_removal);

static const struct super_operations simple_super_operations = {
.statfs  = simple_statfs,
};

static int pseudo_fs_fill_super(struct super_block *s, struct fs_context *fc)
{
struct pseudo_fs_context *ctx = fc->fs_private;
struct inode *root;

s->s_maxbytes = MAX_LFS_FILESIZE;
s->s_blocksize = PAGE_SIZE;
s->s_blocksize_bits = PAGE_SHIFT;
s->s_magic = ctx->magic;
s->s_op = ctx->ops ?: &simple_super_operations;
s->s_export_op = ctx->eops;
s->s_xattr = ctx->xattr;
s->s_time_gran = 1;
root = new_inode(s);
if (!root)
  return -ENOMEM;

/*
* since this is the first inode, make it number 1. New inodes created
* after this must take care not to collide with it (by passing
* max_reserved of 1 to iunique).
*/
root->i_ino = 1;
root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
simple_inode_init_ts(root);
s->s_root = d_make_root(root);
if (!s->s_root)
  return -ENOMEM;
set_default_d_op(s, ctx->dops);
return 0;
}

static int pseudo_fs_get_tree(struct fs_context *fc)
{
return get_tree_nodev(fc, pseudo_fs_fill_super);
}

static void pseudo_fs_free(struct fs_context *fc)
{
kfree(fc->fs_private);
}

static const struct fs_context_operations pseudo_fs_context_ops = {
.free  = pseudo_fs_free,
.get_tree = pseudo_fs_get_tree,
};

/*
* Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
* will never be mountable)
*/
struct pseudo_fs_context *init_pseudo(struct fs_context *fc,
     unsigned long magic)
{
struct pseudo_fs_context *ctx;

ctx = kzalloc(sizeof(struct pseudo_fs_context), GFP_KERNEL);
if (likely(ctx)) {
  ctx->magic = magic;
  fc->fs_private = ctx;
  fc->ops = &pseudo_fs_context_ops;
  fc->sb_flags |= SB_NOUSER;
  fc->global = true;
}
return ctx;
}
EXPORT_SYMBOL(init_pseudo);

int simple_open(struct inode *inode, struct file *file)
{
if (inode->i_private)
  file->private_data = inode->i_private;
return 0;
}
EXPORT_SYMBOL(simple_open);

int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
{
struct inode *inode = d_inode(old_dentry);

inode_set_mtime_to_ts(dir,
         inode_set_ctime_to_ts(dir, inode_set_ctime_current(inode)));
inc_nlink(inode);
ihold(inode);
dget(dentry);
d_instantiate(dentry, inode);
return 0;
}
EXPORT_SYMBOL(simple_link);

int simple_empty(struct dentry *dentry)
{
struct dentry *child;
int ret = 0;

spin_lock(&dentry->d_lock);
hlist_for_each_entry(child, &dentry->d_children, d_sib) {
  spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
  if (simple_positive(child)) {
   spin_unlock(&child->d_lock);
   goto out;
  }
  spin_unlock(&child->d_lock);
}
ret = 1;
out:
spin_unlock(&dentry->d_lock);
return ret;
}
EXPORT_SYMBOL(simple_empty);

int simple_unlink(struct inode *dir, struct dentry *dentry)
{
struct inode *inode = d_inode(dentry);

inode_set_mtime_to_ts(dir,
         inode_set_ctime_to_ts(dir, inode_set_ctime_current(inode)));
drop_nlink(inode);
dput(dentry);
return 0;
}
EXPORT_SYMBOL(simple_unlink);

int simple_rmdir(struct inode *dir, struct dentry *dentry)
{
if (!simple_empty(dentry))
  return -ENOTEMPTY;

drop_nlink(d_inode(dentry));
simple_unlink(dir, dentry);
drop_nlink(dir);
return 0;
}
EXPORT_SYMBOL(simple_rmdir);

/**
* simple_rename_timestamp - update the various inode timestamps for rename
* @old_dir: old parent directory
* @old_dentry: dentry that is being renamed
* @new_dir: new parent directory
* @new_dentry: target for rename
*
* POSIX mandates that the old and new parent directories have their ctime and
* mtime updated, and that inodes of @old_dentry and @new_dentry (if any), have
* their ctime updated.
*/
void simple_rename_timestamp(struct inode *old_dir, struct dentry *old_dentry,
        struct inode *new_dir, struct dentry *new_dentry)
{
struct inode *newino = d_inode(new_dentry);

inode_set_mtime_to_ts(old_dir, inode_set_ctime_current(old_dir));
if (new_dir != old_dir)
  inode_set_mtime_to_ts(new_dir,
          inode_set_ctime_current(new_dir));
inode_set_ctime_current(d_inode(old_dentry));
if (newino)
  inode_set_ctime_current(newino);
}
EXPORT_SYMBOL_GPL(simple_rename_timestamp);

int simple_rename_exchange(struct inode *old_dir, struct dentry *old_dentry,
      struct inode *new_dir, struct dentry *new_dentry)
{
bool old_is_dir = d_is_dir(old_dentry);
bool new_is_dir = d_is_dir(new_dentry);

if (old_dir != new_dir && old_is_dir != new_is_dir) {
  if (old_is_dir) {
   drop_nlink(old_dir);
   inc_nlink(new_dir);
  } else {
   drop_nlink(new_dir);
   inc_nlink(old_dir);
  }
}
simple_rename_timestamp(old_dir, old_dentry, new_dir, new_dentry);
return 0;
}
EXPORT_SYMBOL_GPL(simple_rename_exchange);

int simple_rename(struct mnt_idmap *idmap, struct inode *old_dir,
    struct dentry *old_dentry, struct inode *new_dir,
    struct dentry *new_dentry, unsigned int flags)
{
int they_are_dirs = d_is_dir(old_dentry);

if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
  return -EINVAL;

if (flags & RENAME_EXCHANGE)
  return simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);

if (!simple_empty(new_dentry))
  return -ENOTEMPTY;

if (d_really_is_positive(new_dentry)) {
  simple_unlink(new_dir, new_dentry);
  if (they_are_dirs) {
   drop_nlink(d_inode(new_dentry));
   drop_nlink(old_dir);
  }
} else if (they_are_dirs) {
  drop_nlink(old_dir);
  inc_nlink(new_dir);
}

simple_rename_timestamp(old_dir, old_dentry, new_dir, new_dentry);
return 0;
}
EXPORT_SYMBOL(simple_rename);

/**
* simple_setattr - setattr for simple filesystem
* @idmap: idmap of the target mount
* @dentry: dentry
* @iattr: iattr structure
*
* Returns 0 on success, -error on failure.
*
* simple_setattr is a simple ->setattr implementation without a proper
* implementation of size changes.
*
* It can either be used for in-memory filesystems or special files
* on simple regular filesystems.  Anything that needs to change on-disk
* or wire state on size changes needs its own setattr method.
*/
int simple_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
     struct iattr *iattr)
{
struct inode *inode = d_inode(dentry);
int error;

error = setattr_prepare(idmap, dentry, iattr);
if (error)
  return error;

if (iattr->ia_valid & ATTR_SIZE)
  truncate_setsize(inode, iattr->ia_size);
setattr_copy(idmap, inode, iattr);
mark_inode_dirty(inode);
return 0;
}
EXPORT_SYMBOL(simple_setattr);

static int simple_read_folio(struct file *file, struct folio *folio)
{
folio_zero_range(folio, 0, folio_size(folio));
flush_dcache_folio(folio);
folio_mark_uptodate(folio);
folio_unlock(folio);
return 0;
}

int simple_write_begin(const struct kiocb *iocb, struct address_space *mapping,
   loff_t pos, unsigned len,
   struct folio **foliop, void **fsdata)
{
struct folio *folio;

folio = __filemap_get_folio(mapping, pos / PAGE_SIZE, FGP_WRITEBEGIN,
   mapping_gfp_mask(mapping));
if (IS_ERR(folio))
  return PTR_ERR(folio);

*foliop = folio;

if (!folio_test_uptodate(folio) && (len != folio_size(folio))) {
  size_t from = offset_in_folio(folio, pos);

  folio_zero_segments(folio, 0, from,
    from + len, folio_size(folio));
}
return 0;
}
EXPORT_SYMBOL(simple_write_begin);

/**
* simple_write_end - .write_end helper for non-block-device FSes
* @iocb: kernel I/O control block
* @mapping: "
* @pos: "
* @len: "
* @copied: "
* @folio: "
* @fsdata: "
*
* simple_write_end does the minimum needed for updating a folio after
* writing is done. It has the same API signature as the .write_end of
* address_space_operations vector. So it can just be set onto .write_end for
* FSes that don't need any other processing. i_rwsem is assumed to be held
* exclusively.
* Block based filesystems should use generic_write_end().
* NOTE: Even though i_size might get updated by this function, mark_inode_dirty
* is not called, so a filesystem that actually does store data in .write_inode
* should extend on what's done here with a call to mark_inode_dirty() in the
* case that i_size has changed.
*
* Use *ONLY* with simple_read_folio()
*/
static int simple_write_end(const struct kiocb *iocb,
       struct address_space *mapping,
       loff_t pos, unsigned len, unsigned copied,
       struct folio *folio, void *fsdata)
{
struct inode *inode = folio->mapping->host;
loff_t last_pos = pos + copied;

/* zero the stale part of the folio if we did a short copy */
if (!folio_test_uptodate(folio)) {
  if (copied < len) {
   size_t from = offset_in_folio(folio, pos);

   folio_zero_range(folio, from + copied, len - copied);
  }
  folio_mark_uptodate(folio);
}
/*
* No need to use i_size_read() here, the i_size
* cannot change under us because we hold the i_rwsem.
*/
if (last_pos > inode->i_size)
  i_size_write(inode, last_pos);

folio_mark_dirty(folio);
folio_unlock(folio);
folio_put(folio);

return copied;
}

/*
* Provides ramfs-style behavior: data in the pagecache, but no writeback.
*/
const struct address_space_operations ram_aops = {
.read_folio = simple_read_folio,
.write_begin = simple_write_begin,
.write_end = simple_write_end,
.dirty_folio = noop_dirty_folio,
};
EXPORT_SYMBOL(ram_aops);

/*
* the inodes created here are not hashed. If you use iunique to generate
* unique inode values later for this filesystem, then you must take care
* to pass it an appropriate max_reserved value to avoid collisions.
*/
int simple_fill_super(struct super_block *s, unsigned long magic,
        const struct tree_descr *files)
{
struct inode *inode;
struct dentry *dentry;
int i;

s->s_blocksize = PAGE_SIZE;
s->s_blocksize_bits = PAGE_SHIFT;
s->s_magic = magic;
s->s_op = &simple_super_operations;
s->s_time_gran = 1;

inode = new_inode(s);
if (!inode)
  return -ENOMEM;
/*
* because the root inode is 1, the files array must not contain an
* entry at index 1
*/
inode->i_ino = 1;
inode->i_mode = S_IFDIR | 0755;
simple_inode_init_ts(inode);
inode->i_op = &simple_dir_inode_operations;
inode->i_fop = &simple_dir_operations;
set_nlink(inode, 2);
s->s_root = d_make_root(inode);
if (!s->s_root)
  return -ENOMEM;
for (i = 0; !files->name || files->name[0]; i++, files++) {
  if (!files->name)
   continue;

  /* warn if it tries to conflict with the root inode */
  if (unlikely(i == 1))
   printk(KERN_WARNING "%s: %s passed in a files array"
    "with an index of 1!\n", __func__,
    s->s_type->name);

  dentry = d_alloc_name(s->s_root, files->name);
  if (!dentry)
   return -ENOMEM;
  inode = new_inode(s);
  if (!inode) {
   dput(dentry);
   return -ENOMEM;
  }
  inode->i_mode = S_IFREG | files->mode;
  simple_inode_init_ts(inode);
  inode->i_fop = files->ops;
  inode->i_ino = i;
  d_add(dentry, inode);
}
return 0;
}
EXPORT_SYMBOL(simple_fill_super);

static DEFINE_SPINLOCK(pin_fs_lock);

int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
{
struct vfsmount *mnt = NULL;
spin_lock(&pin_fs_lock);
if (unlikely(!*mount)) {
  spin_unlock(&pin_fs_lock);
  mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
  if (IS_ERR(mnt))
   return PTR_ERR(mnt);
  spin_lock(&pin_fs_lock);
  if (!*mount)
   *mount = mnt;
}
mntget(*mount);
++*count;
spin_unlock(&pin_fs_lock);
mntput(mnt);
return 0;
}
EXPORT_SYMBOL(simple_pin_fs);

void simple_release_fs(struct vfsmount **mount, int *count)
{
struct vfsmount *mnt;
spin_lock(&pin_fs_lock);
mnt = *mount;
if (!--*count)
  *mount = NULL;
spin_unlock(&pin_fs_lock);
mntput(mnt);
}
EXPORT_SYMBOL(simple_release_fs);

/**
* simple_read_from_buffer - copy data from the buffer to user space
* @to: the user space buffer to read to
* @count: the maximum number of bytes to read
* @ppos: the current position in the buffer
* @from: the buffer to read from
* @available: the size of the buffer
*
* The simple_read_from_buffer() function reads up to @count bytes from the
* buffer @from at offset @ppos into the user space address starting at @to.
*
* On success, the number of bytes read is returned and the offset @ppos is
* advanced by this number, or negative value is returned on error.
**/
ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
    const void *from, size_t available)
{
loff_t pos = *ppos;
size_t ret;

if (pos < 0)
  return -EINVAL;
if (pos >= available || !count)
  return 0;
if (count > available - pos)
  count = available - pos;
ret = copy_to_user(to, from + pos, count);
if (ret == count)
  return -EFAULT;
count -= ret;
*ppos = pos + count;
return count;
}
EXPORT_SYMBOL(simple_read_from_buffer);

/**
* simple_write_to_buffer - copy data from user space to the buffer
* @to: the buffer to write to
* @available: the size of the buffer
* @ppos: the current position in the buffer
* @from: the user space buffer to read from
* @count: the maximum number of bytes to read
*
* The simple_write_to_buffer() function reads up to @count bytes from the user
* space address starting at @from into the buffer @to at offset @ppos.
*
* On success, the number of bytes written is returned and the offset @ppos is
* advanced by this number, or negative value is returned on error.
**/
ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
  const void __user *from, size_t count)
{
loff_t pos = *ppos;
size_t res;

if (pos < 0)
  return -EINVAL;
if (pos >= available || !count)
  return 0;
if (count > available - pos)
  count = available - pos;
res = copy_from_user(to + pos, from, count);
if (res == count)
  return -EFAULT;
count -= res;
*ppos = pos + count;
return count;
}
EXPORT_SYMBOL(simple_write_to_buffer);

/**
* memory_read_from_buffer - copy data from the buffer
* @to: the kernel space buffer to read to
* @count: the maximum number of bytes to read
* @ppos: the current position in the buffer
* @from: the buffer to read from
* @available: the size of the buffer
*
* The memory_read_from_buffer() function reads up to @count bytes from the
* buffer @from at offset @ppos into the kernel space address starting at @to.
*
* On success, the number of bytes read is returned and the offset @ppos is
* advanced by this number, or negative value is returned on error.
**/
ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
    const void *from, size_t available)
{
loff_t pos = *ppos;

if (pos < 0)
  return -EINVAL;
if (pos >= available)
  return 0;
if (count > available - pos)
  count = available - pos;
memcpy(to, from + pos, count);
*ppos = pos + count;

return count;
}
EXPORT_SYMBOL(memory_read_from_buffer);

/*
* Transaction based IO.
* The file expects a single write which triggers the transaction, and then
* possibly a read which collects the result - which is stored in a
* file-local buffer.
*/

void simple_transaction_set(struct file *file, size_t n)
{
struct simple_transaction_argresp *ar = file->private_data;

BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);

/*
* The barrier ensures that ar->size will really remain zero until
* ar->data is ready for reading.
*/
smp_mb();
ar->size = n;
}
EXPORT_SYMBOL(simple_transaction_set);

char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
{
struct simple_transaction_argresp *ar;
static DEFINE_SPINLOCK(simple_transaction_lock);

if (size > SIMPLE_TRANSACTION_LIMIT - 1)
  return ERR_PTR(-EFBIG);

ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
if (!ar)
  return ERR_PTR(-ENOMEM);

spin_lock(&simple_transaction_lock);

/* only one write allowed per open */
if (file->private_data) {
  spin_unlock(&simple_transaction_lock);
  free_page((unsigned long)ar);
  return ERR_PTR(-EBUSY);
}

file->private_data = ar;

spin_unlock(&simple_transaction_lock);

if (copy_from_user(ar->data, buf, size))
  return ERR_PTR(-EFAULT);

return ar->data;
}
EXPORT_SYMBOL(simple_transaction_get);

ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
{
struct simple_transaction_argresp *ar = file->private_data;

if (!ar)
  return 0;
return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
}
EXPORT_SYMBOL(simple_transaction_read);

int simple_transaction_release(struct inode *inode, struct file *file)
{
free_page((unsigned long)file->private_data);
return 0;
}
EXPORT_SYMBOL(simple_transaction_release);

/* Simple attribute files */

struct simple_attr {
int (*get)(void *, u64 *);
int (*set)(void *, u64);
char get_buf[24]; /* enough to store a u64 and "\n\0" */
char set_buf[24];
void *data;
const char *fmt; /* format for read operation */
struct mutex mutex; /* protects access to these buffers */
};

/* simple_attr_open is called by an actual attribute open file operation
* to set the attribute specific access operations. */
int simple_attr_open(struct inode *inode, struct file *file,
       int (*get)(void *, u64 *), int (*set)(void *, u64),
       const char *fmt)
{
struct simple_attr *attr;

attr = kzalloc(sizeof(*attr), GFP_KERNEL);
if (!attr)
  return -ENOMEM;

attr->get = get;
attr->set = set;
attr->data = inode->i_private;
attr->fmt = fmt;
mutex_init(&attr->mutex);

file->private_data = attr;

return nonseekable_open(inode, file);
}
EXPORT_SYMBOL_GPL(simple_attr_open);

int simple_attr_release(struct inode *inode, struct file *file)
{
kfree(file->private_data);
return 0;
}
EXPORT_SYMBOL_GPL(simple_attr_release); /* GPL-only?  This?  Really? */

/* read from the buffer that is filled with the get function */
ssize_t simple_attr_read(struct file *file, char __user *buf,
    size_t len, loff_t *ppos)
{
struct simple_attr *attr;
size_t size;
ssize_t ret;

attr = file->private_data;

if (!attr->get)
  return -EACCES;

ret = mutex_lock_interruptible(&attr->mutex);
if (ret)
  return ret;

if (*ppos && attr->get_buf[0]) {
  /* continued read */
  size = strlen(attr->get_buf);
} else {
  /* first read */
  u64 val;
  ret = attr->get(attr->data, &val);
  if (ret)
   goto out;

  size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
     attr->fmt, (unsigned long long)val);
}

ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
out:
mutex_unlock(&attr->mutex);
return ret;
}
EXPORT_SYMBOL_GPL(simple_attr_read);

/* interpret the buffer as a number to call the set function with */
static ssize_t simple_attr_write_xsigned(struct file *file, const char __user *buf,
     size_t len, loff_t *ppos, bool is_signed)
{
struct simple_attr *attr;
unsigned long long val;
size_t size;
ssize_t ret;

attr = file->private_data;
if (!attr->set)
  return -EACCES;

ret = mutex_lock_interruptible(&attr->mutex);
if (ret)
  return ret;

ret = -EFAULT;
size = min(sizeof(attr->set_buf) - 1, len);
if (copy_from_user(attr->set_buf, buf, size))
  goto out;

attr->set_buf[size] = '\0';
if (is_signed)
  ret = kstrtoll(attr->set_buf, 0, &val);
else
  ret = kstrtoull(attr->set_buf, 0, &val);
if (ret)
  goto out;
ret = attr->set(attr->data, val);
if (ret == 0)
  ret = len; /* on success, claim we got the whole input */
out:
mutex_unlock(&attr->mutex);
return ret;
}

ssize_t simple_attr_write(struct file *file, const char __user *buf,
     size_t len, loff_t *ppos)
{
return simple_attr_write_xsigned(file, buf, len, ppos, false);
}
EXPORT_SYMBOL_GPL(simple_attr_write);

ssize_t simple_attr_write_signed(struct file *file, const char __user *buf,
     size_t len, loff_t *ppos)
{
return simple_attr_write_xsigned(file, buf, len, ppos, true);
}
EXPORT_SYMBOL_GPL(simple_attr_write_signed);

/**
* generic_encode_ino32_fh - generic export_operations->encode_fh function
* @inode:   the object to encode
* @fh:      where to store the file handle fragment
* @max_len: maximum length to store there (in 4 byte units)
* @parent:  parent directory inode, if wanted
*
* This generic encode_fh function assumes that the 32 inode number
* is suitable for locating an inode, and that the generation number
* can be used to check that it is still valid.  It places them in the
* filehandle fragment where export_decode_fh expects to find them.
*/
int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
       struct inode *parent)
{
struct fid *fid = (void *)fh;
int len = *max_len;
int type = FILEID_INO32_GEN;

if (parent && (len < 4)) {
  *max_len = 4;
  return FILEID_INVALID;
} else if (len < 2) {
  *max_len = 2;
  return FILEID_INVALID;
}

len = 2;
fid->i32.ino = inode->i_ino;
fid->i32.gen = inode->i_generation;
if (parent) {
  fid->i32.parent_ino = parent->i_ino;
  fid->i32.parent_gen = parent->i_generation;
  len = 4;
  type = FILEID_INO32_GEN_PARENT;
}
*max_len = len;
return type;
}
EXPORT_SYMBOL_GPL(generic_encode_ino32_fh);

/**
* generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
* @sb: filesystem to do the file handle conversion on
* @fid: file handle to convert
* @fh_len: length of the file handle in bytes
* @fh_type: type of file handle
* @get_inode: filesystem callback to retrieve inode
*
* This function decodes @fid as long as it has one of the well-known
* Linux filehandle types and calls @get_inode on it to retrieve the
* inode for the object specified in the file handle.
*/
struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid,
  int fh_len, int fh_type, struct inode *(*get_inode)
   (struct super_block *sb, u64 ino, u32 gen))
{
struct inode *inode = NULL;

if (fh_len < 2)
  return NULL;

switch (fh_type) {
case FILEID_INO32_GEN:
case FILEID_INO32_GEN_PARENT:
  inode = get_inode(sb, fid->i32.ino, fid->i32.gen);
  break;
}

return d_obtain_alias(inode);
}
EXPORT_SYMBOL_GPL(generic_fh_to_dentry);

/**
* generic_fh_to_parent - generic helper for the fh_to_parent export operation
* @sb: filesystem to do the file handle conversion on
* @fid: file handle to convert
* @fh_len: length of the file handle in bytes
* @fh_type: type of file handle
* @get_inode: filesystem callback to retrieve inode
*
* This function decodes @fid as long as it has one of the well-known
* Linux filehandle types and calls @get_inode on it to retrieve the
* inode for the _parent_ object specified in the file handle if it
* is specified in the file handle, or NULL otherwise.
*/
struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
  int fh_len, int fh_type, struct inode *(*get_inode)
   (struct super_block *sb, u64 ino, u32 gen))
{
struct inode *inode = NULL;

if (fh_len <= 2)
  return NULL;

switch (fh_type) {
case FILEID_INO32_GEN_PARENT:
  inode = get_inode(sb, fid->i32.parent_ino,
      (fh_len > 3 ? fid->i32.parent_gen : 0));
  break;
}

return d_obtain_alias(inode);
}
EXPORT_SYMBOL_GPL(generic_fh_to_parent);

/**
* __generic_file_fsync - generic fsync implementation for simple filesystems
*
* @file: file to synchronize
* @start: start offset in bytes
* @end: end offset in bytes (inclusive)
* @datasync: only synchronize essential metadata if true
*
* This is a generic implementation of the fsync method for simple
* filesystems which track all non-inode metadata in the buffers list
* hanging off the address_space structure.
*/
int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
     int datasync)
{
struct inode *inode = file->f_mapping->host;
int err;
int ret;

err = file_write_and_wait_range(file, start, end);
if (err)
  return err;

inode_lock(inode);
ret = sync_mapping_buffers(inode->i_mapping);
if (!(inode->i_state & I_DIRTY_ALL))
  goto out;
if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
  goto out;

err = sync_inode_metadata(inode, 1);
if (ret == 0)
  ret = err;

out:
inode_unlock(inode);
/* check and advance again to catch errors after syncing out buffers */
err = file_check_and_advance_wb_err(file);
if (ret == 0)
  ret = err;
return ret;
}
EXPORT_SYMBOL(__generic_file_fsync);

/**
* generic_file_fsync - generic fsync implementation for simple filesystems
* with flush
* @file: file to synchronize
* @start: start offset in bytes
* @end: end offset in bytes (inclusive)
* @datasync: only synchronize essential metadata if true
*
*/

int generic_file_fsync(struct file *file, loff_t start, loff_t end,
         int datasync)
{
struct inode *inode = file->f_mapping->host;
int err;

err = __generic_file_fsync(file, start, end, datasync);
if (err)
  return err;
return blkdev_issue_flush(inode->i_sb->s_bdev);
}
EXPORT_SYMBOL(generic_file_fsync);

/**
* generic_check_addressable - Check addressability of file system
* @blocksize_bits: log of file system block size
* @num_blocks: number of blocks in file system
*
* Determine whether a file system with @num_blocks blocks (and a
* block size of 2**@blocksize_bits) is addressable by the sector_t
* and page cache of the system.  Return 0 if so and -EFBIG otherwise.
*/
int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
{
u64 last_fs_block = num_blocks - 1;
u64 last_fs_page, max_bytes;

if (check_shl_overflow(num_blocks, blocksize_bits, &max_bytes))
  return -EFBIG;

last_fs_page = (max_bytes >> PAGE_SHIFT) - 1;

if (unlikely(num_blocks == 0))
  return 0;

if (blocksize_bits < 9)
  return -EINVAL;

if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
     (last_fs_page > (pgoff_t)(~0ULL))) {
  return -EFBIG;
}
return 0;
}
EXPORT_SYMBOL(generic_check_addressable);

/*
* No-op implementation of ->fsync for in-memory filesystems.
*/
int noop_fsync(struct file *file, loff_t start, loff_t end, int datasync)
{
return 0;
}
EXPORT_SYMBOL(noop_fsync);

ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
{
/*
* iomap based filesystems support direct I/O without need for
* this callback. However, it still needs to be set in
* inode->a_ops so that open/fcntl know that direct I/O is
* generally supported.
*/
return -EINVAL;
}
EXPORT_SYMBOL_GPL(noop_direct_IO);

/* Because kfree isn't assignment-compatible with void(void*) ;-/ */
void kfree_link(void *p)
{
kfree(p);
}
EXPORT_SYMBOL(kfree_link);

struct inode *alloc_anon_inode(struct super_block *s)
{
static const struct address_space_operations anon_aops = {
  .dirty_folio = noop_dirty_folio,
};
struct inode *inode = new_inode_pseudo(s);

if (!inode)
  return ERR_PTR(-ENOMEM);

inode->i_ino = get_next_ino();
inode->i_mapping->a_ops = &anon_aops;

/*
* Mark the inode dirty from the very beginning,
* that way it will never be moved to the dirty
* list because mark_inode_dirty() will think
* that it already _is_ on the dirty list.
*/
inode->i_state = I_DIRTY;
/*
* Historically anonymous inodes don't have a type at all and
* userspace has come to rely on this.
*/
inode->i_mode = S_IRUSR | S_IWUSR;
inode->i_uid = current_fsuid();
inode->i_gid = current_fsgid();
inode->i_flags |= S_PRIVATE | S_ANON_INODE;
simple_inode_init_ts(inode);
return inode;
}
EXPORT_SYMBOL(alloc_anon_inode);

/**
* simple_nosetlease - generic helper for prohibiting leases
* @filp: file pointer
* @arg: type of lease to obtain
* @flp: new lease supplied for insertion
* @priv: private data for lm_setup operation
*
* Generic helper for filesystems that do not wish to allow leases to be set.
* All arguments are ignored and it just returns -EINVAL.
*/
int
simple_nosetlease(struct file *filp, int arg, struct file_lease **flp,
    void **priv)
{
return -EINVAL;
}
EXPORT_SYMBOL(simple_nosetlease);

/**
* simple_get_link - generic helper to get the target of "fast" symlinks
* @dentry: not used here
* @inode: the symlink inode
* @done: not used here
*
* Generic helper for filesystems to use for symlink inodes where a pointer to
* the symlink target is stored in ->i_link.  NOTE: this isn't normally called,
* since as an optimization the path lookup code uses any non-NULL ->i_link
* directly, without calling ->get_link().  But ->get_link() still must be set,
* to mark the inode_operations as being for a symlink.
*
* Return: the symlink target
*/
const char *simple_get_link(struct dentry *dentry, struct inode *inode,
       struct delayed_call *done)
{
return inode->i_link;
}
EXPORT_SYMBOL(simple_get_link);

const struct inode_operations simple_symlink_inode_operations = {
.get_link = simple_get_link,
};
EXPORT_SYMBOL(simple_symlink_inode_operations);

/*
* Operations for a permanently empty directory.
*/
static struct dentry *empty_dir_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
{
return ERR_PTR(-ENOENT);
}

static int empty_dir_setattr(struct mnt_idmap *idmap,
        struct dentry *dentry, struct iattr *attr)
{
return -EPERM;
}

static ssize_t empty_dir_listxattr(struct dentry *dentry, char *list, size_t size)
{
return -EOPNOTSUPP;
}

static const struct inode_operations empty_dir_inode_operations = {
.lookup  = empty_dir_lookup,
.setattr = empty_dir_setattr,
.listxattr = empty_dir_listxattr,
};

static loff_t empty_dir_llseek(struct file *file, loff_t offset, int whence)
{
/* An empty directory has two entries . and .. at offsets 0 and 1 */
return generic_file_llseek_size(file, offset, whence, 2, 2);
}

static int empty_dir_readdir(struct file *file, struct dir_context *ctx)
{
dir_emit_dots(file, ctx);
return 0;
}

static const struct file_operations empty_dir_operations = {
.llseek  = empty_dir_llseek,
.read  = generic_read_dir,
.iterate_shared = empty_dir_readdir,
.fsync  = noop_fsync,
};

void make_empty_dir_inode(struct inode *inode)
{
set_nlink(inode, 2);
inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
inode->i_uid = GLOBAL_ROOT_UID;
inode->i_gid = GLOBAL_ROOT_GID;
inode->i_rdev = 0;
inode->i_size = 0;
inode->i_blkbits = PAGE_SHIFT;
inode->i_blocks = 0;

inode->i_op = &empty_dir_inode_operations;
inode->i_opflags &= ~IOP_XATTR;
inode->i_fop = &empty_dir_operations;
}

bool is_empty_dir_inode(struct inode *inode)
{
return (inode->i_fop == &empty_dir_operations) &&
  (inode->i_op == &empty_dir_inode_operations);
}

#if IS_ENABLED(CONFIG_UNICODE)
/**
* generic_ci_d_compare - generic d_compare implementation for casefolding filesystems
* @dentry: dentry whose name we are checking against
* @len: len of name of dentry
* @str: str pointer to name of dentry
* @name: Name to compare against
*
* Return: 0 if names match, 1 if mismatch, or -ERRNO
*/
int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
    const char *str, const struct qstr *name)
{
const struct dentry *parent;
const struct inode *dir;
union shortname_store strbuf;
struct qstr qstr;

/*
* Attempt a case-sensitive match first. It is cheaper and
* should cover most lookups, including all the sane
* applications that expect a case-sensitive filesystem.
*
* This comparison is safe under RCU because the caller
* guarantees the consistency between str and len. See
* __d_lookup_rcu_op_compare() for details.
*/
if (len == name->len && !memcmp(str, name->name, len))
  return 0;

parent = READ_ONCE(dentry->d_parent);
dir = READ_ONCE(parent->d_inode);
if (!dir || !IS_CASEFOLDED(dir))
  return 1;

qstr.len = len;
qstr.name = str;
/*
* If the dentry name is stored in-line, then it may be concurrently
* modified by a rename.  If this happens, the VFS will eventually retry
* the lookup, so it doesn't matter what ->d_compare() returns.
* However, it's unsafe to call utf8_strncasecmp() with an unstable
* string.  Therefore, we have to copy the name into a temporary buffer.
* As above, len is guaranteed to match str, so the shortname case
* is exactly when str points to ->d_shortname.
*/
if (qstr.name == dentry->d_shortname.string) {
  strbuf = dentry->d_shortname; // NUL is guaranteed to be in there
  qstr.name = strbuf.string;
  /* prevent compiler from optimizing out the temporary buffer */
  barrier();
}

return utf8_strncasecmp(dentry->d_sb->s_encoding, name, &qstr);
}
EXPORT_SYMBOL(generic_ci_d_compare);

/**
* generic_ci_d_hash - generic d_hash implementation for casefolding filesystems
* @dentry: dentry of the parent directory
* @str: qstr of name whose hash we should fill in
*
* Return: 0 if hash was successful or unchanged, and -EINVAL on error
*/
int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)
{
const struct inode *dir = READ_ONCE(dentry->d_inode);
struct super_block *sb = dentry->d_sb;
const struct unicode_map *um = sb->s_encoding;
int ret;

if (!dir || !IS_CASEFOLDED(dir))
  return 0;

ret = utf8_casefold_hash(um, dentry, str);
if (ret < 0 && sb_has_strict_encoding(sb))
  return -EINVAL;
return 0;
}
EXPORT_SYMBOL(generic_ci_d_hash);

static const struct dentry_operations generic_ci_dentry_ops = {
.d_hash = generic_ci_d_hash,
.d_compare = generic_ci_d_compare,
#ifdef CONFIG_FS_ENCRYPTION
.d_revalidate = fscrypt_d_revalidate,
#endif
};

/**
* generic_ci_match() - Match a name (case-insensitively) with a dirent.
* This is a filesystem helper for comparison with directory entries.
* generic_ci_d_compare should be used in VFS' ->d_compare instead.
*
* @parent: Inode of the parent of the dirent under comparison
* @name: name under lookup.
* @folded_name: Optional pre-folded name under lookup
* @de_name: Dirent name.
* @de_name_len: dirent name length.
*
* Test whether a case-insensitive directory entry matches the filename
* being searched.  If @folded_name is provided, it is used instead of
* recalculating the casefold of @name.
*
* Return: > 0 if the directory entry matches, 0 if it doesn't match, or
* < 0 on error.
*/
int generic_ci_match(const struct inode *parent,
       const struct qstr *name,
       const struct qstr *folded_name,
       const u8 *de_name, u32 de_name_len)
{
const struct super_block *sb = parent->i_sb;
const struct unicode_map *um = sb->s_encoding;
struct fscrypt_str decrypted_name = FSTR_INIT(NULL, de_name_len);
struct qstr dirent = QSTR_INIT(de_name, de_name_len);
int res = 0;

if (IS_ENCRYPTED(parent)) {
  const struct fscrypt_str encrypted_name =
   FSTR_INIT((u8 *) de_name, de_name_len);

  if (WARN_ON_ONCE(!fscrypt_has_encryption_key(parent)))
   return -EINVAL;

  decrypted_name.name = kmalloc(de_name_len, GFP_KERNEL);
  if (!decrypted_name.name)
   return -ENOMEM;
  res = fscrypt_fname_disk_to_usr(parent, 0, 0, &encrypted_name,
      &decrypted_name);
  if (res < 0) {
   kfree(decrypted_name.name);
   return res;
  }
  dirent.name = decrypted_name.name;
  dirent.len = decrypted_name.len;
}

/*
* Attempt a case-sensitive match first. It is cheaper and
* should cover most lookups, including all the sane
* applications that expect a case-sensitive filesystem.
*/

if (dirent.len == name->len &&
     !memcmp(name->name, dirent.name, dirent.len))
  goto out;

if (folded_name->name)
  res = utf8_strncasecmp_folded(um, folded_name, &dirent);
else
  res = utf8_strncasecmp(um, name, &dirent);

out:
kfree(decrypted_name.name);
if (res < 0 && sb_has_strict_encoding(sb)) {
  pr_err_ratelimited("Directory contains filename that is invalid UTF-8");
  return 0;
}
return !res;
}
EXPORT_SYMBOL(generic_ci_match);
#endif

#ifdef CONFIG_FS_ENCRYPTION
static const struct dentry_operations generic_encrypted_dentry_ops = {
.d_revalidate = fscrypt_d_revalidate,
};
#endif

/**
* generic_set_sb_d_ops - helper for choosing the set of
* filesystem-wide dentry operations for the enabled features
* @sb: superblock to be configured
*
* Filesystems supporting casefolding and/or fscrypt can call this
* helper at mount-time to configure default dentry_operations to the
* best set of dentry operations required for the enabled features.
* The helper must be called after these have been configured, but
* before the root dentry is created.
*/
void generic_set_sb_d_ops(struct super_block *sb)
{
#if IS_ENABLED(CONFIG_UNICODE)
if (sb->s_encoding) {
  set_default_d_op(sb, &generic_ci_dentry_ops);
  return;
}
#endif
#ifdef CONFIG_FS_ENCRYPTION
if (sb->s_cop) {
  set_default_d_op(sb, &generic_encrypted_dentry_ops);
  return;
}
#endif
}
EXPORT_SYMBOL(generic_set_sb_d_ops);

/**
* inode_maybe_inc_iversion - increments i_version
* @inode: inode with the i_version that should be updated
* @force: increment the counter even if it's not necessary?
*
* Every time the inode is modified, the i_version field must be seen to have
* changed by any observer.
*
* If "force" is set or the QUERIED flag is set, then ensure that we increment
* the value, and clear the queried flag.
*
* In the common case where neither is set, then we can return "false" without
* updating i_version.
*
* If this function returns false, and no other metadata has changed, then we
* can avoid logging the metadata.
*/
bool inode_maybe_inc_iversion(struct inode *inode, bool force)
{
u64 cur, new;

/*
* The i_version field is not strictly ordered with any other inode
* information, but the legacy inode_inc_iversion code used a spinlock
* to serialize increments.
*
* We add a full memory barrier to ensure that any de facto ordering
* with other state is preserved (either implicitly coming from cmpxchg
* or explicitly from smp_mb if we don't know upfront if we will execute
* the former).
*
* These barriers pair with inode_query_iversion().
*/
cur = inode_peek_iversion_raw(inode);
if (!force && !(cur & I_VERSION_QUERIED)) {
  smp_mb();
  cur = inode_peek_iversion_raw(inode);
}

do {
  /* If flag is clear then we needn't do anything */
  if (!force && !(cur & I_VERSION_QUERIED))
   return false;

  /* Since lowest bit is flag, add 2 to avoid it */
  new = (cur & ~I_VERSION_QUERIED) + I_VERSION_INCREMENT;
} while (!atomic64_try_cmpxchg(&inode->i_version, &cur, new));
return true;
}
EXPORT_SYMBOL(inode_maybe_inc_iversion);

/**
* inode_query_iversion - read i_version for later use
* @inode: inode from which i_version should be read
*
* Read the inode i_version counter. This should be used by callers that wish
* to store the returned i_version for later comparison. This will guarantee
* that a later query of the i_version will result in a different value if
* anything has changed.
*
* In this implementation, we fetch the current value, set the QUERIED flag and
* then try to swap it into place with a cmpxchg, if it wasn't already set. If
* that fails, we try again with the newly fetched value from the cmpxchg.
*/
u64 inode_query_iversion(struct inode *inode)
{
u64 cur, new;
bool fenced = false;

/*
* Memory barriers (implicit in cmpxchg, explicit in smp_mb) pair with
* inode_maybe_inc_iversion(), see that routine for more details.
*/
cur = inode_peek_iversion_raw(inode);
do {
  /* If flag is already set, then no need to swap */
  if (cur & I_VERSION_QUERIED) {
   if (!fenced)
    smp_mb();
   break;
  }

  fenced = true;
  new = cur | I_VERSION_QUERIED;
} while (!atomic64_try_cmpxchg(&inode->i_version, &cur, new));
return cur >> I_VERSION_QUERIED_SHIFT;
}
EXPORT_SYMBOL(inode_query_iversion);

ssize_t direct_write_fallback(struct kiocb *iocb, struct iov_iter *iter,
  ssize_t direct_written, ssize_t buffered_written)
{
struct address_space *mapping = iocb->ki_filp->f_mapping;
loff_t pos = iocb->ki_pos - buffered_written;
loff_t end = iocb->ki_pos - 1;
int err;

/*
* If the buffered write fallback returned an error, we want to return
* the number of bytes which were written by direct I/O, or the error
* code if that was zero.
*
* Note that this differs from normal direct-io semantics, which will
* return -EFOO even if some bytes were written.
*/
if (unlikely(buffered_written < 0)) {
  if (direct_written)
   return direct_written;
  return buffered_written;
}

/*
* We need to ensure that the page cache pages are written to disk and
* invalidated to preserve the expected O_DIRECT semantics.
*/
err = filemap_write_and_wait_range(mapping, pos, end);
if (err < 0) {
  /*
* We don't know how much we wrote, so just return the number of
* bytes which were direct-written
*/
  iocb->ki_pos -= buffered_written;
  if (direct_written)
   return direct_written;
  return err;
}
invalidate_mapping_pages(mapping, pos >> PAGE_SHIFT, end >> PAGE_SHIFT);
return direct_written + buffered_written;
}
EXPORT_SYMBOL_GPL(direct_write_fallback);

/**
* simple_inode_init_ts - initialize the timestamps for a new inode
* @inode: inode to be initialized
*
* When a new inode is created, most filesystems set the timestamps to the
* current time. Add a helper to do this.
*/
struct timespec64 simple_inode_init_ts(struct inode *inode)
{
struct timespec64 ts = inode_set_ctime_current(inode);

inode_set_atime_to_ts(inode, ts);
inode_set_mtime_to_ts(inode, ts);
return ts;
}
EXPORT_SYMBOL(simple_inode_init_ts);

struct dentry *stashed_dentry_get(struct dentry **stashed)
{
struct dentry *dentry;

guard(rcu)();
dentry = rcu_dereference(*stashed);
if (!dentry)
  return NULL;
if (IS_ERR(dentry))
  return dentry;
if (!lockref_get_not_dead(&dentry->d_lockref))
  return NULL;
return dentry;
}

static struct dentry *prepare_anon_dentry(struct dentry **stashed,
       struct super_block *sb,
       void *data)
{
struct dentry *dentry;
struct inode *inode;
const struct stashed_operations *sops = sb->s_fs_info;
int ret;

inode = new_inode_pseudo(sb);
if (!inode) {
  sops->put_data(data);
  return ERR_PTR(-ENOMEM);
}

inode->i_flags |= S_IMMUTABLE;
inode->i_mode = S_IFREG;
simple_inode_init_ts(inode);

ret = sops->init_inode(inode, data);
if (ret < 0) {
  iput(inode);
  return ERR_PTR(ret);
}

/* Notice when this is changed. */
WARN_ON_ONCE(!S_ISREG(inode->i_mode));

dentry = d_alloc_anon(sb);
if (!dentry) {
  iput(inode);
  return ERR_PTR(-ENOMEM);
}

/* Store address of location where dentry's supposed to be stashed. */
dentry->d_fsdata = stashed;

/* @data is now owned by the fs */
d_instantiate(dentry, inode);
return dentry;
}

struct dentry *stash_dentry(struct dentry **stashed, struct dentry *dentry)
{
guard(rcu)();
for (;;) {
  struct dentry *old;

  /* Assume any old dentry was cleared out. */
  old = cmpxchg(stashed, NULL, dentry);
  if (likely(!old))
   return dentry;

  /* Check if somebody else installed a reusable dentry. */
  if (lockref_get_not_dead(&old->d_lockref))
   return old;

  /* There's an old dead dentry there, try to take it over. */
  if (likely(try_cmpxchg(stashed, &old, dentry)))
   return dentry;
}
}

/**
* path_from_stashed - create path from stashed or new dentry
* @stashed:    where to retrieve or stash dentry
* @mnt:        mnt of the filesystems to use
* @data:       data to store in inode->i_private
* @path:       path to create
*
* The function tries to retrieve a stashed dentry from @stashed. If the dentry
* is still valid then it will be reused. If the dentry isn't able the function
* will allocate a new dentry and inode. It will then check again whether it
* can reuse an existing dentry in case one has been added in the meantime or
* update @stashed with the newly added dentry.
*
* Special-purpose helper for nsfs and pidfs.
*
* Return: On success zero and on failure a negative error is returned.
*/
int path_from_stashed(struct dentry **stashed, struct vfsmount *mnt, void *data,
        struct path *path)
{
struct dentry *dentry, *res;
const struct stashed_operations *sops = mnt->mnt_sb->s_fs_info;

/* See if dentry can be reused. */
res = stashed_dentry_get(stashed);
if (IS_ERR(res))
  return PTR_ERR(res);
if (res) {
  sops->put_data(data);
  goto make_path;
}

/* Allocate a new dentry. */
dentry = prepare_anon_dentry(stashed, mnt->mnt_sb, data);
if (IS_ERR(dentry))
  return PTR_ERR(dentry);

/* Added a new dentry. @data is now owned by the filesystem. */
if (sops->stash_dentry)
  res = sops->stash_dentry(stashed, dentry);
else
  res = stash_dentry(stashed, dentry);
if (IS_ERR(res)) {
  dput(dentry);
  return PTR_ERR(res);
}
if (res != dentry)
  dput(dentry);

make_path:
path->dentry = res;
path->mnt = mntget(mnt);
VFS_WARN_ON_ONCE(path->dentry->d_fsdata != stashed);
VFS_WARN_ON_ONCE(d_inode(path->dentry)->i_private != data);
return 0;
}

void stashed_dentry_prune(struct dentry *dentry)
{
struct dentry **stashed = dentry->d_fsdata;
struct inode *inode = d_inode(dentry);

if (WARN_ON_ONCE(!stashed))
  return;

if (!inode)
  return;

/*
* Only replace our own @dentry as someone else might've
* already cleared out @dentry and stashed their own
* dentry in there.
*/
cmpxchg(stashed, dentry, NULL);
}

/* parent must be held exclusive */
struct dentry *simple_start_creating(struct dentry *parent, const char *name)
{
struct dentry *dentry;
struct inode *dir = d_inode(parent);

inode_lock(dir);
if (unlikely(IS_DEADDIR(dir))) {
  inode_unlock(dir);
  return ERR_PTR(-ENOENT);
}
dentry = lookup_noperm(&QSTR(name), parent);
if (IS_ERR(dentry)) {
  inode_unlock(dir);
  return dentry;
}
if (dentry->d_inode) {
  dput(dentry);
  inode_unlock(dir);
  return ERR_PTR(-EEXIST);
}
return dentry;
}
EXPORT_SYMBOL(simple_start_creating);

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