WSL2-Linux-Kernel/fs/overlayfs/util.c

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14 KiB
C
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/*
* Copyright (C) 2011 Novell Inc.
* Copyright (C) 2016 Red Hat, Inc.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 as published by
* the Free Software Foundation.
*/
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/xattr.h>
#include <linux/exportfs.h>
#include <linux/uuid.h>
#include <linux/namei.h>
#include <linux/ratelimit.h>
#include "overlayfs.h"
int ovl_want_write(struct dentry *dentry)
{
struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
return mnt_want_write(ofs->upper_mnt);
}
void ovl_drop_write(struct dentry *dentry)
{
struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
mnt_drop_write(ofs->upper_mnt);
}
struct dentry *ovl_workdir(struct dentry *dentry)
{
struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
return ofs->workdir;
}
const struct cred *ovl_override_creds(struct super_block *sb)
{
struct ovl_fs *ofs = sb->s_fs_info;
return override_creds(ofs->creator_cred);
}
struct super_block *ovl_same_sb(struct super_block *sb)
{
struct ovl_fs *ofs = sb->s_fs_info;
return ofs->same_sb;
}
bool ovl_can_decode_fh(struct super_block *sb)
{
return (sb->s_export_op && sb->s_export_op->fh_to_dentry &&
!uuid_is_null(&sb->s_uuid));
}
struct dentry *ovl_indexdir(struct super_block *sb)
{
struct ovl_fs *ofs = sb->s_fs_info;
return ofs->indexdir;
}
struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
{
size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
if (oe)
oe->numlower = numlower;
return oe;
}
bool ovl_dentry_remote(struct dentry *dentry)
{
return dentry->d_flags &
(DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
DCACHE_OP_REAL);
}
bool ovl_dentry_weird(struct dentry *dentry)
{
return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
DCACHE_MANAGE_TRANSIT |
DCACHE_OP_HASH |
DCACHE_OP_COMPARE);
}
enum ovl_path_type ovl_path_type(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
enum ovl_path_type type = 0;
if (ovl_dentry_upper(dentry)) {
type = __OVL_PATH_UPPER;
/*
* Non-dir dentry can hold lower dentry of its copy up origin.
*/
if (oe->numlower) {
type |= __OVL_PATH_ORIGIN;
if (d_is_dir(dentry))
type |= __OVL_PATH_MERGE;
}
} else {
if (oe->numlower > 1)
type |= __OVL_PATH_MERGE;
}
return type;
}
void ovl_path_upper(struct dentry *dentry, struct path *path)
{
struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
path->mnt = ofs->upper_mnt;
path->dentry = ovl_dentry_upper(dentry);
}
void ovl_path_lower(struct dentry *dentry, struct path *path)
{
struct ovl_entry *oe = dentry->d_fsdata;
if (oe->numlower) {
path->mnt = oe->lowerstack[0].layer->mnt;
path->dentry = oe->lowerstack[0].dentry;
} else {
*path = (struct path) { };
}
}
enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
{
enum ovl_path_type type = ovl_path_type(dentry);
if (!OVL_TYPE_UPPER(type))
ovl_path_lower(dentry, path);
else
ovl_path_upper(dentry, path);
return type;
}
struct dentry *ovl_dentry_upper(struct dentry *dentry)
{
return ovl_upperdentry_dereference(OVL_I(d_inode(dentry)));
}
struct dentry *ovl_dentry_lower(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
return oe->numlower ? oe->lowerstack[0].dentry : NULL;
}
struct dentry *ovl_dentry_real(struct dentry *dentry)
{
return ovl_dentry_upper(dentry) ?: ovl_dentry_lower(dentry);
}
struct dentry *ovl_i_dentry_upper(struct inode *inode)
{
return ovl_upperdentry_dereference(OVL_I(inode));
}
struct inode *ovl_inode_upper(struct inode *inode)
{
struct dentry *upperdentry = ovl_i_dentry_upper(inode);
return upperdentry ? d_inode(upperdentry) : NULL;
}
struct inode *ovl_inode_lower(struct inode *inode)
{
return OVL_I(inode)->lower;
}
struct inode *ovl_inode_real(struct inode *inode)
{
return ovl_inode_upper(inode) ?: ovl_inode_lower(inode);
}
struct ovl_dir_cache *ovl_dir_cache(struct inode *inode)
{
return OVL_I(inode)->cache;
}
void ovl_set_dir_cache(struct inode *inode, struct ovl_dir_cache *cache)
{
OVL_I(inode)->cache = cache;
}
bool ovl_dentry_is_opaque(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
return oe->opaque;
}
bool ovl_dentry_is_whiteout(struct dentry *dentry)
{
return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
}
void ovl_dentry_set_opaque(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
oe->opaque = true;
}
/*
* For hard links it's possible for ovl_dentry_upper() to return positive, while
* there's no actual upper alias for the inode. Copy up code needs to know
* about the existence of the upper alias, so it can't use ovl_dentry_upper().
*/
bool ovl_dentry_has_upper_alias(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
return oe->has_upper;
}
void ovl_dentry_set_upper_alias(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
oe->has_upper = true;
}
bool ovl_redirect_dir(struct super_block *sb)
{
struct ovl_fs *ofs = sb->s_fs_info;
return ofs->config.redirect_dir && !ofs->noxattr;
}
const char *ovl_dentry_get_redirect(struct dentry *dentry)
{
return OVL_I(d_inode(dentry))->redirect;
}
void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
{
struct ovl_inode *oi = OVL_I(d_inode(dentry));
kfree(oi->redirect);
oi->redirect = redirect;
}
void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
struct dentry *lowerdentry)
{
if (upperdentry)
OVL_I(inode)->__upperdentry = upperdentry;
if (lowerdentry)
OVL_I(inode)->lower = d_inode(lowerdentry);
ovl_copyattr(d_inode(upperdentry ?: lowerdentry), inode);
}
void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
{
struct inode *upperinode = d_inode(upperdentry);
WARN_ON(OVL_I(inode)->__upperdentry);
/*
* Make sure upperdentry is consistent before making it visible
*/
smp_wmb();
OVL_I(inode)->__upperdentry = upperdentry;
if (!S_ISDIR(upperinode->i_mode) && inode_unhashed(inode)) {
inode->i_private = upperinode;
__insert_inode_hash(inode, (unsigned long) upperinode);
}
}
void ovl_dentry_version_inc(struct dentry *dentry, bool impurity)
{
struct inode *inode = d_inode(dentry);
WARN_ON(!inode_is_locked(inode));
/*
* Version is used by readdir code to keep cache consistent. For merge
* dirs all changes need to be noted. For non-merge dirs, cache only
* contains impure (ones which have been copied up and have origins)
* entries, so only need to note changes to impure entries.
*/
if (OVL_TYPE_MERGE(ovl_path_type(dentry)) || impurity)
OVL_I(inode)->version++;
}
u64 ovl_dentry_version_get(struct dentry *dentry)
{
struct inode *inode = d_inode(dentry);
WARN_ON(!inode_is_locked(inode));
return OVL_I(inode)->version;
}
bool ovl_is_whiteout(struct dentry *dentry)
{
struct inode *inode = dentry->d_inode;
return inode && IS_WHITEOUT(inode);
}
struct file *ovl_path_open(struct path *path, int flags)
{
return dentry_open(path, flags | O_NOATIME, current_cred());
}
int ovl_copy_up_start(struct dentry *dentry)
{
struct ovl_inode *oi = OVL_I(d_inode(dentry));
int err;
err = mutex_lock_interruptible(&oi->lock);
if (!err && ovl_dentry_has_upper_alias(dentry)) {
err = 1; /* Already copied up */
mutex_unlock(&oi->lock);
}
return err;
}
void ovl_copy_up_end(struct dentry *dentry)
{
mutex_unlock(&OVL_I(d_inode(dentry))->lock);
}
bool ovl_check_origin_xattr(struct dentry *dentry)
{
int res;
res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0);
/* Zero size value means "copied up but origin unknown" */
if (res >= 0)
return true;
return false;
}
bool ovl_check_dir_xattr(struct dentry *dentry, const char *name)
{
int res;
char val;
if (!d_is_dir(dentry))
return false;
res = vfs_getxattr(dentry, name, &val, 1);
if (res == 1 && val == 'y')
return true;
return false;
}
int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
const char *name, const void *value, size_t size,
int xerr)
{
int err;
struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
if (ofs->noxattr)
return xerr;
err = ovl_do_setxattr(upperdentry, name, value, size, 0);
if (err == -EOPNOTSUPP) {
pr_warn("overlayfs: cannot set %s xattr on upper\n", name);
ofs->noxattr = true;
return xerr;
}
return err;
}
int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry)
{
int err;
if (ovl_test_flag(OVL_IMPURE, d_inode(dentry)))
return 0;
/*
* Do not fail when upper doesn't support xattrs.
* Upper inodes won't have origin nor redirect xattr anyway.
*/
err = ovl_check_setxattr(dentry, upperdentry, OVL_XATTR_IMPURE,
"y", 1, 0);
if (!err)
ovl_set_flag(OVL_IMPURE, d_inode(dentry));
return err;
}
void ovl_set_flag(unsigned long flag, struct inode *inode)
{
set_bit(flag, &OVL_I(inode)->flags);
}
void ovl_clear_flag(unsigned long flag, struct inode *inode)
{
clear_bit(flag, &OVL_I(inode)->flags);
}
bool ovl_test_flag(unsigned long flag, struct inode *inode)
{
return test_bit(flag, &OVL_I(inode)->flags);
}
/**
* Caller must hold a reference to inode to prevent it from being freed while
* it is marked inuse.
*/
bool ovl_inuse_trylock(struct dentry *dentry)
{
struct inode *inode = d_inode(dentry);
bool locked = false;
spin_lock(&inode->i_lock);
if (!(inode->i_state & I_OVL_INUSE)) {
inode->i_state |= I_OVL_INUSE;
locked = true;
}
spin_unlock(&inode->i_lock);
return locked;
}
void ovl_inuse_unlock(struct dentry *dentry)
{
if (dentry) {
struct inode *inode = d_inode(dentry);
spin_lock(&inode->i_lock);
WARN_ON(!(inode->i_state & I_OVL_INUSE));
inode->i_state &= ~I_OVL_INUSE;
spin_unlock(&inode->i_lock);
}
}
/* Caller must hold OVL_I(inode)->lock */
static void ovl_cleanup_index(struct dentry *dentry)
{
struct inode *dir = ovl_indexdir(dentry->d_sb)->d_inode;
struct dentry *lowerdentry = ovl_dentry_lower(dentry);
struct dentry *upperdentry = ovl_dentry_upper(dentry);
struct dentry *index = NULL;
struct inode *inode;
struct qstr name;
int err;
err = ovl_get_index_name(lowerdentry, &name);
if (err)
goto fail;
inode = d_inode(upperdentry);
if (inode->i_nlink != 1) {
pr_warn_ratelimited("overlayfs: cleanup linked index (%pd2, ino=%lu, nlink=%u)\n",
upperdentry, inode->i_ino, inode->i_nlink);
/*
* We either have a bug with persistent union nlink or a lower
* hardlink was added while overlay is mounted. Adding a lower
* hardlink and then unlinking all overlay hardlinks would drop
* overlay nlink to zero before all upper inodes are unlinked.
* As a safety measure, when that situation is detected, set
* the overlay nlink to the index inode nlink minus one for the
* index entry itself.
*/
set_nlink(d_inode(dentry), inode->i_nlink - 1);
ovl_set_nlink_upper(dentry);
goto out;
}
inode_lock_nested(dir, I_MUTEX_PARENT);
/* TODO: whiteout instead of cleanup to block future open by handle */
index = lookup_one_len(name.name, ovl_indexdir(dentry->d_sb), name.len);
err = PTR_ERR(index);
if (!IS_ERR(index))
err = ovl_cleanup(dir, index);
else
index = NULL;
inode_unlock(dir);
if (err)
goto fail;
out:
dput(index);
return;
fail:
pr_err("overlayfs: cleanup index of '%pd2' failed (%i)\n", dentry, err);
goto out;
}
/*
* Operations that change overlay inode and upper inode nlink need to be
* synchronized with copy up for persistent nlink accounting.
*/
int ovl_nlink_start(struct dentry *dentry, bool *locked)
{
struct ovl_inode *oi = OVL_I(d_inode(dentry));
const struct cred *old_cred;
int err;
if (!d_inode(dentry) || d_is_dir(dentry))
return 0;
/*
* With inodes index is enabled, we store the union overlay nlink
* in an xattr on the index inode. When whiting out lower hardlinks
* we need to decrement the overlay persistent nlink, but before the
* first copy up, we have no upper index inode to store the xattr.
*
* As a workaround, before whiteout/rename over of a lower hardlink,
* copy up to create the upper index. Creating the upper index will
* initialize the overlay nlink, so it could be dropped if unlink
* or rename succeeds.
*
* TODO: implement metadata only index copy up when called with
* ovl_copy_up_flags(dentry, O_PATH).
*/
if (ovl_indexdir(dentry->d_sb) && !ovl_dentry_has_upper_alias(dentry) &&
d_inode(ovl_dentry_lower(dentry))->i_nlink > 1) {
err = ovl_copy_up(dentry);
if (err)
return err;
}
err = mutex_lock_interruptible(&oi->lock);
if (err)
return err;
if (!ovl_test_flag(OVL_INDEX, d_inode(dentry)))
goto out;
old_cred = ovl_override_creds(dentry->d_sb);
/*
* The overlay inode nlink should be incremented/decremented IFF the
* upper operation succeeds, along with nlink change of upper inode.
* Therefore, before link/unlink/rename, we store the union nlink
* value relative to the upper inode nlink in an upper inode xattr.
*/
err = ovl_set_nlink_upper(dentry);
revert_creds(old_cred);
out:
if (err)
mutex_unlock(&oi->lock);
else
*locked = true;
return err;
}
void ovl_nlink_end(struct dentry *dentry, bool locked)
{
if (locked) {
if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) &&
d_inode(dentry)->i_nlink == 0) {
const struct cred *old_cred;
old_cred = ovl_override_creds(dentry->d_sb);
ovl_cleanup_index(dentry);
revert_creds(old_cred);
}
mutex_unlock(&OVL_I(d_inode(dentry))->lock);
}
}
int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir)
{
/* Workdir should not be the same as upperdir */
if (workdir == upperdir)
goto err;
/* Workdir should not be subdir of upperdir and vice versa */
if (lock_rename(workdir, upperdir) != NULL)
goto err_unlock;
return 0;
err_unlock:
unlock_rename(workdir, upperdir);
err:
pr_err("overlayfs: failed to lock workdir+upperdir\n");
return -EIO;
}