mirror of
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-04-13 09:59:31 +00:00
5be1fa8abd
->d_revalidate() often needs to access dentry parent and name; that has to be done carefully, since the locking environment varies from caller to caller. We are not guaranteed that dentry in question will not be moved right under us - not unless the filesystem is such that nothing on it ever gets renamed. It can be dealt with, but that results in boilerplate code that isn't even needed - the callers normally have just found the dentry via dcache lookup and want to verify that it's in the right place; they already have the values of ->d_parent and ->d_name stable. There is a couple of exceptions (overlayfs and, to less extent, ecryptfs), but for the majority of calls that song and dance is not needed at all. It's easier to make ecryptfs and overlayfs find and pass those values if there's a ->d_revalidate() instance to be called, rather than doing that in the instances. This commit only changes the calling conventions; making use of supplied values is left to followups. NOTE: some instances need more than just the parent - things like CIFS may need to build an entire path from filesystem root, so they need more precautions than the usual boilerplate. This series doesn't do anything to that need - these filesystems have to keep their locking mechanisms (rename_lock loops, use of dentry_path_raw(), private rwsem a-la v9fs). One thing to keep in mind when using name is that name->name will normally point into the pathname being resolved; the filename in question occupies name->len bytes starting at name->name, and there is NUL somewhere after it, but it the next byte might very well be '/' rather than '\0'. Do not ignore name->len. Reviewed-by: Jeff Layton <jlayton@kernel.org> Reviewed-by: Gabriel Krisman Bertazi <gabriel@krisman.be> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
88 lines
2.3 KiB
C
88 lines
2.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
|
|
/*
|
|
* eCryptfs: Linux filesystem encryption layer
|
|
*
|
|
* Copyright (C) 1997-2003 Erez Zadok
|
|
* Copyright (C) 2001-2003 Stony Brook University
|
|
* Copyright (C) 2004-2006 International Business Machines Corp.
|
|
* Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
|
|
*/
|
|
|
|
#include <linux/dcache.h>
|
|
#include <linux/namei.h>
|
|
#include <linux/mount.h>
|
|
#include <linux/fs_stack.h>
|
|
#include <linux/slab.h>
|
|
#include "ecryptfs_kernel.h"
|
|
|
|
/**
|
|
* ecryptfs_d_revalidate - revalidate an ecryptfs dentry
|
|
* @dir: inode of expected parent
|
|
* @name: expected name
|
|
* @dentry: dentry to revalidate
|
|
* @flags: lookup flags
|
|
*
|
|
* Called when the VFS needs to revalidate a dentry. This
|
|
* is called whenever a name lookup finds a dentry in the
|
|
* dcache. Most filesystems leave this as NULL, because all their
|
|
* dentries in the dcache are valid.
|
|
*
|
|
* Returns 1 if valid, 0 otherwise.
|
|
*
|
|
*/
|
|
static int ecryptfs_d_revalidate(struct inode *dir, const struct qstr *name,
|
|
struct dentry *dentry, unsigned int flags)
|
|
{
|
|
struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry);
|
|
int rc = 1;
|
|
|
|
if (flags & LOOKUP_RCU)
|
|
return -ECHILD;
|
|
|
|
if (lower_dentry->d_flags & DCACHE_OP_REVALIDATE) {
|
|
struct inode *lower_dir = ecryptfs_inode_to_lower(dir);
|
|
struct name_snapshot n;
|
|
|
|
take_dentry_name_snapshot(&n, lower_dentry);
|
|
rc = lower_dentry->d_op->d_revalidate(lower_dir, &n.name,
|
|
lower_dentry, flags);
|
|
release_dentry_name_snapshot(&n);
|
|
}
|
|
|
|
if (d_really_is_positive(dentry)) {
|
|
struct inode *inode = d_inode(dentry);
|
|
|
|
fsstack_copy_attr_all(inode, ecryptfs_inode_to_lower(inode));
|
|
if (!inode->i_nlink)
|
|
return 0;
|
|
}
|
|
return rc;
|
|
}
|
|
|
|
struct kmem_cache *ecryptfs_dentry_info_cache;
|
|
|
|
static void ecryptfs_dentry_free_rcu(struct rcu_head *head)
|
|
{
|
|
kmem_cache_free(ecryptfs_dentry_info_cache,
|
|
container_of(head, struct ecryptfs_dentry_info, rcu));
|
|
}
|
|
|
|
/**
|
|
* ecryptfs_d_release
|
|
* @dentry: The ecryptfs dentry
|
|
*
|
|
* Called when a dentry is really deallocated.
|
|
*/
|
|
static void ecryptfs_d_release(struct dentry *dentry)
|
|
{
|
|
struct ecryptfs_dentry_info *p = dentry->d_fsdata;
|
|
if (p) {
|
|
path_put(&p->lower_path);
|
|
call_rcu(&p->rcu, ecryptfs_dentry_free_rcu);
|
|
}
|
|
}
|
|
|
|
const struct dentry_operations ecryptfs_dops = {
|
|
.d_revalidate = ecryptfs_d_revalidate,
|
|
.d_release = ecryptfs_d_release,
|
|
};
|