linux/fs/libfs.c
Linus Torvalds 7d6beb71da idmapped-mounts-v5.12
-----BEGIN PGP SIGNATURE-----
 
 iHUEABYKAB0WIQRAhzRXHqcMeLMyaSiRxhvAZXjcogUCYCegywAKCRCRxhvAZXjc
 ouJ6AQDlf+7jCQlQdeKKoN9QDFfMzG1ooemat36EpRRTONaGuAD8D9A4sUsG4+5f
 4IU5Lj9oY4DEmF8HenbWK2ZHsesL2Qg=
 =yPaw
 -----END PGP SIGNATURE-----

Merge tag 'idmapped-mounts-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

Pull idmapped mounts from Christian Brauner:
 "This introduces idmapped mounts which has been in the making for some
  time. Simply put, different mounts can expose the same file or
  directory with different ownership. This initial implementation comes
  with ports for fat, ext4 and with Christoph's port for xfs with more
  filesystems being actively worked on by independent people and
  maintainers.

  Idmapping mounts handle a wide range of long standing use-cases. Here
  are just a few:

   - Idmapped mounts make it possible to easily share files between
     multiple users or multiple machines especially in complex
     scenarios. For example, idmapped mounts will be used in the
     implementation of portable home directories in
     systemd-homed.service(8) where they allow users to move their home
     directory to an external storage device and use it on multiple
     computers where they are assigned different uids and gids. This
     effectively makes it possible to assign random uids and gids at
     login time.

   - It is possible to share files from the host with unprivileged
     containers without having to change ownership permanently through
     chown(2).

   - It is possible to idmap a container's rootfs and without having to
     mangle every file. For example, Chromebooks use it to share the
     user's Download folder with their unprivileged containers in their
     Linux subsystem.

   - It is possible to share files between containers with
     non-overlapping idmappings.

   - Filesystem that lack a proper concept of ownership such as fat can
     use idmapped mounts to implement discretionary access (DAC)
     permission checking.

   - They allow users to efficiently changing ownership on a per-mount
     basis without having to (recursively) chown(2) all files. In
     contrast to chown (2) changing ownership of large sets of files is
     instantenous with idmapped mounts. This is especially useful when
     ownership of a whole root filesystem of a virtual machine or
     container is changed. With idmapped mounts a single syscall
     mount_setattr syscall will be sufficient to change the ownership of
     all files.

   - Idmapped mounts always take the current ownership into account as
     idmappings specify what a given uid or gid is supposed to be mapped
     to. This contrasts with the chown(2) syscall which cannot by itself
     take the current ownership of the files it changes into account. It
     simply changes the ownership to the specified uid and gid. This is
     especially problematic when recursively chown(2)ing a large set of
     files which is commong with the aforementioned portable home
     directory and container and vm scenario.

   - Idmapped mounts allow to change ownership locally, restricting it
     to specific mounts, and temporarily as the ownership changes only
     apply as long as the mount exists.

  Several userspace projects have either already put up patches and
  pull-requests for this feature or will do so should you decide to pull
  this:

   - systemd: In a wide variety of scenarios but especially right away
     in their implementation of portable home directories.

         https://systemd.io/HOME_DIRECTORY/

   - container runtimes: containerd, runC, LXD:To share data between
     host and unprivileged containers, unprivileged and privileged
     containers, etc. The pull request for idmapped mounts support in
     containerd, the default Kubernetes runtime is already up for quite
     a while now: https://github.com/containerd/containerd/pull/4734

   - The virtio-fs developers and several users have expressed interest
     in using this feature with virtual machines once virtio-fs is
     ported.

   - ChromeOS: Sharing host-directories with unprivileged containers.

  I've tightly synced with all those projects and all of those listed
  here have also expressed their need/desire for this feature on the
  mailing list. For more info on how people use this there's a bunch of
  talks about this too. Here's just two recent ones:

      https://www.cncf.io/wp-content/uploads/2020/12/Rootless-Containers-in-Gitpod.pdf
      https://fosdem.org/2021/schedule/event/containers_idmap/

  This comes with an extensive xfstests suite covering both ext4 and
  xfs:

      https://git.kernel.org/brauner/xfstests-dev/h/idmapped_mounts

  It covers truncation, creation, opening, xattrs, vfscaps, setid
  execution, setgid inheritance and more both with idmapped and
  non-idmapped mounts. It already helped to discover an unrelated xfs
  setgid inheritance bug which has since been fixed in mainline. It will
  be sent for inclusion with the xfstests project should you decide to
  merge this.

  In order to support per-mount idmappings vfsmounts are marked with
  user namespaces. The idmapping of the user namespace will be used to
  map the ids of vfs objects when they are accessed through that mount.
  By default all vfsmounts are marked with the initial user namespace.
  The initial user namespace is used to indicate that a mount is not
  idmapped. All operations behave as before and this is verified in the
  testsuite.

  Based on prior discussions we want to attach the whole user namespace
  and not just a dedicated idmapping struct. This allows us to reuse all
  the helpers that already exist for dealing with idmappings instead of
  introducing a whole new range of helpers. In addition, if we decide in
  the future that we are confident enough to enable unprivileged users
  to setup idmapped mounts the permission checking can take into account
  whether the caller is privileged in the user namespace the mount is
  currently marked with.

  The user namespace the mount will be marked with can be specified by
  passing a file descriptor refering to the user namespace as an
  argument to the new mount_setattr() syscall together with the new
  MOUNT_ATTR_IDMAP flag. The system call follows the openat2() pattern
  of extensibility.

  The following conditions must be met in order to create an idmapped
  mount:

   - The caller must currently have the CAP_SYS_ADMIN capability in the
     user namespace the underlying filesystem has been mounted in.

   - The underlying filesystem must support idmapped mounts.

   - The mount must not already be idmapped. This also implies that the
     idmapping of a mount cannot be altered once it has been idmapped.

   - The mount must be a detached/anonymous mount, i.e. it must have
     been created by calling open_tree() with the OPEN_TREE_CLONE flag
     and it must not already have been visible in the filesystem.

  The last two points guarantee easier semantics for userspace and the
  kernel and make the implementation significantly simpler.

  By default vfsmounts are marked with the initial user namespace and no
  behavioral or performance changes are observed.

  The manpage with a detailed description can be found here:

      1d7b902e28

  In order to support idmapped mounts, filesystems need to be changed
  and mark themselves with the FS_ALLOW_IDMAP flag in fs_flags. The
  patches to convert individual filesystem are not very large or
  complicated overall as can be seen from the included fat, ext4, and
  xfs ports. Patches for other filesystems are actively worked on and
  will be sent out separately. The xfstestsuite can be used to verify
  that port has been done correctly.

  The mount_setattr() syscall is motivated independent of the idmapped
  mounts patches and it's been around since July 2019. One of the most
  valuable features of the new mount api is the ability to perform
  mounts based on file descriptors only.

  Together with the lookup restrictions available in the openat2()
  RESOLVE_* flag namespace which we added in v5.6 this is the first time
  we are close to hardened and race-free (e.g. symlinks) mounting and
  path resolution.

  While userspace has started porting to the new mount api to mount
  proper filesystems and create new bind-mounts it is currently not
  possible to change mount options of an already existing bind mount in
  the new mount api since the mount_setattr() syscall is missing.

  With the addition of the mount_setattr() syscall we remove this last
  restriction and userspace can now fully port to the new mount api,
  covering every use-case the old mount api could. We also add the
  crucial ability to recursively change mount options for a whole mount
  tree, both removing and adding mount options at the same time. This
  syscall has been requested multiple times by various people and
  projects.

  There is a simple tool available at

      https://github.com/brauner/mount-idmapped

  that allows to create idmapped mounts so people can play with this
  patch series. I'll add support for the regular mount binary should you
  decide to pull this in the following weeks:

  Here's an example to a simple idmapped mount of another user's home
  directory:

	u1001@f2-vm:/$ sudo ./mount --idmap both:1000:1001:1 /home/ubuntu/ /mnt

	u1001@f2-vm:/$ ls -al /home/ubuntu/
	total 28
	drwxr-xr-x 2 ubuntu ubuntu 4096 Oct 28 22:07 .
	drwxr-xr-x 4 root   root   4096 Oct 28 04:00 ..
	-rw------- 1 ubuntu ubuntu 3154 Oct 28 22:12 .bash_history
	-rw-r--r-- 1 ubuntu ubuntu  220 Feb 25  2020 .bash_logout
	-rw-r--r-- 1 ubuntu ubuntu 3771 Feb 25  2020 .bashrc
	-rw-r--r-- 1 ubuntu ubuntu  807 Feb 25  2020 .profile
	-rw-r--r-- 1 ubuntu ubuntu    0 Oct 16 16:11 .sudo_as_admin_successful
	-rw------- 1 ubuntu ubuntu 1144 Oct 28 00:43 .viminfo

	u1001@f2-vm:/$ ls -al /mnt/
	total 28
	drwxr-xr-x  2 u1001 u1001 4096 Oct 28 22:07 .
	drwxr-xr-x 29 root  root  4096 Oct 28 22:01 ..
	-rw-------  1 u1001 u1001 3154 Oct 28 22:12 .bash_history
	-rw-r--r--  1 u1001 u1001  220 Feb 25  2020 .bash_logout
	-rw-r--r--  1 u1001 u1001 3771 Feb 25  2020 .bashrc
	-rw-r--r--  1 u1001 u1001  807 Feb 25  2020 .profile
	-rw-r--r--  1 u1001 u1001    0 Oct 16 16:11 .sudo_as_admin_successful
	-rw-------  1 u1001 u1001 1144 Oct 28 00:43 .viminfo

	u1001@f2-vm:/$ touch /mnt/my-file

	u1001@f2-vm:/$ setfacl -m u:1001:rwx /mnt/my-file

	u1001@f2-vm:/$ sudo setcap -n 1001 cap_net_raw+ep /mnt/my-file

	u1001@f2-vm:/$ ls -al /mnt/my-file
	-rw-rwxr--+ 1 u1001 u1001 0 Oct 28 22:14 /mnt/my-file

	u1001@f2-vm:/$ ls -al /home/ubuntu/my-file
	-rw-rwxr--+ 1 ubuntu ubuntu 0 Oct 28 22:14 /home/ubuntu/my-file

	u1001@f2-vm:/$ getfacl /mnt/my-file
	getfacl: Removing leading '/' from absolute path names
	# file: mnt/my-file
	# owner: u1001
	# group: u1001
	user::rw-
	user:u1001:rwx
	group::rw-
	mask::rwx
	other::r--

	u1001@f2-vm:/$ getfacl /home/ubuntu/my-file
	getfacl: Removing leading '/' from absolute path names
	# file: home/ubuntu/my-file
	# owner: ubuntu
	# group: ubuntu
	user::rw-
	user:ubuntu:rwx
	group::rw-
	mask::rwx
	other::r--"

* tag 'idmapped-mounts-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: (41 commits)
  xfs: remove the possibly unused mp variable in xfs_file_compat_ioctl
  xfs: support idmapped mounts
  ext4: support idmapped mounts
  fat: handle idmapped mounts
  tests: add mount_setattr() selftests
  fs: introduce MOUNT_ATTR_IDMAP
  fs: add mount_setattr()
  fs: add attr_flags_to_mnt_flags helper
  fs: split out functions to hold writers
  namespace: only take read lock in do_reconfigure_mnt()
  mount: make {lock,unlock}_mount_hash() static
  namespace: take lock_mount_hash() directly when changing flags
  nfs: do not export idmapped mounts
  overlayfs: do not mount on top of idmapped mounts
  ecryptfs: do not mount on top of idmapped mounts
  ima: handle idmapped mounts
  apparmor: handle idmapped mounts
  fs: make helpers idmap mount aware
  exec: handle idmapped mounts
  would_dump: handle idmapped mounts
  ...
2021-02-23 13:39:45 -08:00

1522 lines
40 KiB
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/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/uaccess.h>
#include "internal.h"
int simple_getattr(struct user_namespace *mnt_userns, const struct path *path,
struct kstat *stat, u32 request_mask,
unsigned int query_flags)
{
struct inode *inode = d_inode(path->dentry);
generic_fillattr(&init_user_ns, 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)
{
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);
const struct dentry_operations simple_dentry_operations = {
.d_delete = always_delete_dentry,
};
EXPORT_SYMBOL(simple_dentry_operations);
/*
* 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_sb->s_d_op)
d_set_d_op(dentry, &simple_dentry_operations);
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 list_head *p,
loff_t count,
struct dentry *last)
{
struct dentry *dentry = cursor->d_parent, *found = NULL;
spin_lock(&dentry->d_lock);
while ((p = p->next) != &dentry->d_subdirs) {
struct dentry *d = list_entry(p, struct dentry, d_child);
// 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()) {
list_move(&cursor->d_child, p);
p = &cursor->d_child;
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_subdirs,
offset - 2, NULL);
spin_lock(&dentry->d_lock);
if (to)
list_move(&cursor->d_child, &to->d_child);
else
list_del_init(&cursor->d_child);
spin_unlock(&dentry->d_lock);
dput(to);
file->f_pos = offset;
inode_unlock_shared(dentry->d_inode);
}
return offset;
}
EXPORT_SYMBOL(dcache_dir_lseek);
/* Relationship between i_mode and the DT_xxx types */
static inline unsigned char dt_type(struct inode *inode)
{
return (inode->i_mode >> 12) & 15;
}
/*
* 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 list_head *anchor = &dentry->d_subdirs;
struct dentry *next = NULL;
struct list_head *p;
if (!dir_emit_dots(file, ctx))
return 0;
if (ctx->pos == 2)
p = anchor;
else if (!list_empty(&cursor->d_child))
p = &cursor->d_child;
else
return 0;
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, dt_type(d_inode(next))))
break;
ctx->pos++;
p = &next->d_child;
}
spin_lock(&dentry->d_lock);
if (next)
list_move_tail(&cursor->d_child, &next->d_child);
else
list_del_init(&cursor->d_child);
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);
static struct dentry *find_next_child(struct dentry *parent, struct dentry *prev)
{
struct dentry *child = NULL;
struct list_head *p = prev ? &prev->d_child : &parent->d_subdirs;
spin_lock(&parent->d_lock);
while ((p = p->next) != &parent->d_subdirs) {
struct dentry *d = container_of(p, struct dentry, d_child);
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;
}
void simple_recursive_removal(struct dentry *dentry,
void (*callback)(struct dentry *))
{
struct dentry *this = dget(dentry);
while (true) {
struct dentry *victim = NULL, *child;
struct inode *inode = this->d_inode;
inode_lock(inode);
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->i_ctime = current_time(inode);
clear_nlink(inode);
inode_unlock(inode);
victim = this;
this = this->d_parent;
inode = this->d_inode;
inode_lock(inode);
if (simple_positive(victim)) {
d_invalidate(victim); // avoid lost mounts
if (d_is_dir(victim))
fsnotify_rmdir(inode, victim);
else
fsnotify_unlink(inode, victim);
if (callback)
callback(victim);
dput(victim); // unpin it
}
if (victim == dentry) {
inode->i_ctime = inode->i_mtime =
current_time(inode);
if (d_is_dir(dentry))
drop_nlink(inode);
inode_unlock(inode);
dput(dentry);
return;
}
}
inode_unlock(inode);
this = child;
}
}
EXPORT_SYMBOL(simple_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_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;
root->i_atime = root->i_mtime = root->i_ctime = current_time(root);
s->s_root = d_make_root(root);
if (!s->s_root)
return -ENOMEM;
s->s_d_op = 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->i_ctime = dir->i_ctime = dir->i_mtime = current_time(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);
list_for_each_entry(child, &dentry->d_subdirs, d_child) {
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->i_ctime = dir->i_ctime = dir->i_mtime = current_time(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);
int simple_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
struct dentry *old_dentry, struct inode *new_dir,
struct dentry *new_dentry, unsigned int flags)
{
struct inode *inode = d_inode(old_dentry);
int they_are_dirs = d_is_dir(old_dentry);
if (flags & ~RENAME_NOREPLACE)
return -EINVAL;
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);
}
old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
new_dir->i_mtime = inode->i_ctime = current_time(old_dir);
return 0;
}
EXPORT_SYMBOL(simple_rename);
/**
* simple_setattr - setattr for simple filesystem
* @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 user_namespace *mnt_userns, struct dentry *dentry,
struct iattr *iattr)
{
struct inode *inode = d_inode(dentry);
int error;
error = setattr_prepare(mnt_userns, dentry, iattr);
if (error)
return error;
if (iattr->ia_valid & ATTR_SIZE)
truncate_setsize(inode, iattr->ia_size);
setattr_copy(mnt_userns, inode, iattr);
mark_inode_dirty(inode);
return 0;
}
EXPORT_SYMBOL(simple_setattr);
int simple_readpage(struct file *file, struct page *page)
{
clear_highpage(page);
flush_dcache_page(page);
SetPageUptodate(page);
unlock_page(page);
return 0;
}
EXPORT_SYMBOL(simple_readpage);
int simple_write_begin(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata)
{
struct page *page;
pgoff_t index;
index = pos >> PAGE_SHIFT;
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page)
return -ENOMEM;
*pagep = page;
if (!PageUptodate(page) && (len != PAGE_SIZE)) {
unsigned from = pos & (PAGE_SIZE - 1);
zero_user_segments(page, 0, from, from + len, PAGE_SIZE);
}
return 0;
}
EXPORT_SYMBOL(simple_write_begin);
/**
* simple_write_end - .write_end helper for non-block-device FSes
* @file: See .write_end of address_space_operations
* @mapping: "
* @pos: "
* @len: "
* @copied: "
* @page: "
* @fsdata: "
*
* simple_write_end does the minimum needed for updating a page 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_mutex is assumed to be held.
* 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_readpage()
*/
int simple_write_end(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned copied,
struct page *page, void *fsdata)
{
struct inode *inode = page->mapping->host;
loff_t last_pos = pos + copied;
/* zero the stale part of the page if we did a short copy */
if (!PageUptodate(page)) {
if (copied < len) {
unsigned from = pos & (PAGE_SIZE - 1);
zero_user(page, from + copied, len - copied);
}
SetPageUptodate(page);
}
/*
* No need to use i_size_read() here, the i_size
* cannot change under us because we hold the i_mutex.
*/
if (last_pos > inode->i_size)
i_size_write(inode, last_pos);
set_page_dirty(page);
unlock_page(page);
put_page(page);
return copied;
}
EXPORT_SYMBOL(simple_write_end);
/*
* 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 *root;
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;
inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
inode->i_op = &simple_dir_inode_operations;
inode->i_fop = &simple_dir_operations;
set_nlink(inode, 2);
root = d_make_root(inode);
if (!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(root, files->name);
if (!dentry)
goto out;
inode = new_inode(s);
if (!inode) {
dput(dentry);
goto out;
}
inode->i_mode = S_IFREG | files->mode;
inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
inode->i_fop = files->ops;
inode->i_ino = i;
d_add(dentry, inode);
}
s->s_root = root;
return 0;
out:
d_genocide(root);
shrink_dcache_parent(root);
dput(root);
return -ENOMEM;
}
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 */
ssize_t simple_attr_write(struct file *file, const char __user *buf,
size_t len, loff_t *ppos)
{
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';
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;
}
EXPORT_SYMBOL_GPL(simple_attr_write);
/**
* 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 =
last_fs_block >> (PAGE_SHIFT - blocksize_bits);
if (unlikely(num_blocks == 0))
return 0;
if ((blocksize_bits < 9) || (blocksize_bits > PAGE_SHIFT))
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);
int noop_set_page_dirty(struct page *page)
{
/*
* Unlike __set_page_dirty_no_writeback that handles dirty page
* tracking in the page object, dax does all dirty tracking in
* the inode address_space in response to mkwrite faults. In the
* dax case we only need to worry about potentially dirty CPU
* caches, not dirty page cache pages to write back.
*
* This callback is defined to prevent fallback to
* __set_page_dirty_buffers() in set_page_dirty().
*/
return 0;
}
EXPORT_SYMBOL_GPL(noop_set_page_dirty);
void noop_invalidatepage(struct page *page, unsigned int offset,
unsigned int length)
{
/*
* There is no page cache to invalidate in the dax case, however
* we need this callback defined to prevent falling back to
* block_invalidatepage() in do_invalidatepage().
*/
}
EXPORT_SYMBOL_GPL(noop_invalidatepage);
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);
/*
* nop .set_page_dirty method so that people can use .page_mkwrite on
* anon inodes.
*/
static int anon_set_page_dirty(struct page *page)
{
return 0;
};
struct inode *alloc_anon_inode(struct super_block *s)
{
static const struct address_space_operations anon_aops = {
.set_page_dirty = anon_set_page_dirty,
};
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;
inode->i_mode = S_IRUSR | S_IWUSR;
inode->i_uid = current_fsuid();
inode->i_gid = current_fsgid();
inode->i_flags |= S_PRIVATE;
inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(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, long arg, struct file_lock **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_getattr(struct user_namespace *mnt_userns,
const struct path *path, struct kstat *stat,
u32 request_mask, unsigned int query_flags)
{
struct inode *inode = d_inode(path->dentry);
generic_fillattr(&init_user_ns, inode, stat);
return 0;
}
static int empty_dir_setattr(struct user_namespace *mnt_userns,
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,
.permission = generic_permission,
.setattr = empty_dir_setattr,
.getattr = empty_dir_getattr,
.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);
}
#ifdef CONFIG_UNICODE
/*
* Determine if the name of a dentry should be casefolded.
*
* Return: if names will need casefolding
*/
static bool needs_casefold(const struct inode *dir)
{
return IS_CASEFOLDED(dir) && dir->i_sb->s_encoding;
}
/**
* 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
*/
static int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
const char *str, const struct qstr *name)
{
const struct dentry *parent = READ_ONCE(dentry->d_parent);
const struct inode *dir = READ_ONCE(parent->d_inode);
const struct super_block *sb = dentry->d_sb;
const struct unicode_map *um = sb->s_encoding;
struct qstr qstr = QSTR_INIT(str, len);
char strbuf[DNAME_INLINE_LEN];
int ret;
if (!dir || !needs_casefold(dir))
goto fallback;
/*
* 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.
*/
if (len <= DNAME_INLINE_LEN - 1) {
memcpy(strbuf, str, len);
strbuf[len] = 0;
qstr.name = strbuf;
/* prevent compiler from optimizing out the temporary buffer */
barrier();
}
ret = utf8_strncasecmp(um, name, &qstr);
if (ret >= 0)
return ret;
if (sb_has_strict_encoding(sb))
return -EINVAL;
fallback:
if (len != name->len)
return 1;
return !!memcmp(str, name->name, len);
}
/**
* 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
*/
static 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 = 0;
if (!dir || !needs_casefold(dir))
return 0;
ret = utf8_casefold_hash(um, dentry, str);
if (ret < 0 && sb_has_strict_encoding(sb))
return -EINVAL;
return 0;
}
static const struct dentry_operations generic_ci_dentry_ops = {
.d_hash = generic_ci_d_hash,
.d_compare = generic_ci_d_compare,
};
#endif
#ifdef CONFIG_FS_ENCRYPTION
static const struct dentry_operations generic_encrypted_dentry_ops = {
.d_revalidate = fscrypt_d_revalidate,
};
#endif
#if defined(CONFIG_FS_ENCRYPTION) && defined(CONFIG_UNICODE)
static const struct dentry_operations generic_encrypted_ci_dentry_ops = {
.d_hash = generic_ci_d_hash,
.d_compare = generic_ci_d_compare,
.d_revalidate = fscrypt_d_revalidate,
};
#endif
/**
* generic_set_encrypted_ci_d_ops - helper for setting d_ops for given dentry
* @dentry: dentry to set ops on
*
* Casefolded directories need d_hash and d_compare set, so that the dentries
* contained in them are handled case-insensitively. Note that these operations
* are needed on the parent directory rather than on the dentries in it, and
* while the casefolding flag can be toggled on and off on an empty directory,
* dentry_operations can't be changed later. As a result, if the filesystem has
* casefolding support enabled at all, we have to give all dentries the
* casefolding operations even if their inode doesn't have the casefolding flag
* currently (and thus the casefolding ops would be no-ops for now).
*
* Encryption works differently in that the only dentry operation it needs is
* d_revalidate, which it only needs on dentries that have the no-key name flag.
* The no-key flag can't be set "later", so we don't have to worry about that.
*
* Finally, to maximize compatibility with overlayfs (which isn't compatible
* with certain dentry operations) and to avoid taking an unnecessary
* performance hit, we use custom dentry_operations for each possible
* combination rather than always installing all operations.
*/
void generic_set_encrypted_ci_d_ops(struct dentry *dentry)
{
#ifdef CONFIG_FS_ENCRYPTION
bool needs_encrypt_ops = dentry->d_flags & DCACHE_NOKEY_NAME;
#endif
#ifdef CONFIG_UNICODE
bool needs_ci_ops = dentry->d_sb->s_encoding;
#endif
#if defined(CONFIG_FS_ENCRYPTION) && defined(CONFIG_UNICODE)
if (needs_encrypt_ops && needs_ci_ops) {
d_set_d_op(dentry, &generic_encrypted_ci_dentry_ops);
return;
}
#endif
#ifdef CONFIG_FS_ENCRYPTION
if (needs_encrypt_ops) {
d_set_d_op(dentry, &generic_encrypted_dentry_ops);
return;
}
#endif
#ifdef CONFIG_UNICODE
if (needs_ci_ops) {
d_set_d_op(dentry, &generic_ci_dentry_ops);
return;
}
#endif
}
EXPORT_SYMBOL(generic_set_encrypted_ci_d_ops);