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// SPDX-License-Identifier: GPL-2.0-only
/*
* fs/kernfs/mount.c - kernfs mount implementation
*
* Copyright (c) 2001-3 Patrick Mochel
* Copyright (c) 2007 SUSE Linux Products GmbH
* Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
*/
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/init.h>
#include <linux/magic.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/namei.h>
#include <linux/seq_file.h>
#include <linux/exportfs.h>
#include "kernfs-internal.h"
struct kmem_cache *kernfs_node_cache, *kernfs_iattrs_cache;
static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
{
struct kernfs_root *root = kernfs_root(kernfs_dentry_node(dentry));
struct kernfs_syscall_ops *scops = root->syscall_ops;
if (scops && scops->show_options)
return scops->show_options(sf, root);
return 0;
}
static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry)
{
struct kernfs_node *node = kernfs_dentry_node(dentry);
struct kernfs_root *root = kernfs_root(node);
struct kernfs_syscall_ops *scops = root->syscall_ops;
if (scops && scops->show_path)
return scops->show_path(sf, node, root);
seq_dentry(sf, dentry, " \t\n\\");
return 0;
}
const struct super_operations kernfs_sops = {
.statfs = simple_statfs,
.drop_inode = generic_delete_inode,
.evict_inode = kernfs_evict_inode,
.show_options = kernfs_sop_show_options,
.show_path = kernfs_sop_show_path,
};
/*
* Similar to kernfs_fh_get_inode, this one gets kernfs node from inode
* number and generation
*/
struct kernfs_node *kernfs_get_node_by_id(struct kernfs_root *root,
const union kernfs_node_id *id)
{
struct kernfs_node *kn;
kn = kernfs_find_and_get_node_by_ino(root, id->ino);
if (!kn)
return NULL;
if (kn->id.generation != id->generation) {
kernfs_put(kn);
return NULL;
}
return kn;
}
static struct inode *kernfs_fh_get_inode(struct super_block *sb,
u64 ino, u32 generation)
{
struct kernfs_super_info *info = kernfs_info(sb);
struct inode *inode;
struct kernfs_node *kn;
if (ino == 0)
return ERR_PTR(-ESTALE);
kn = kernfs_find_and_get_node_by_ino(info->root, ino);
if (!kn)
return ERR_PTR(-ESTALE);
inode = kernfs_get_inode(sb, kn);
kernfs_put(kn);
if (!inode)
return ERR_PTR(-ESTALE);
if (generation && inode->i_generation != generation) {
/* we didn't find the right inode.. */
iput(inode);
return ERR_PTR(-ESTALE);
}
return inode;
}
static struct dentry *kernfs_fh_to_dentry(struct super_block *sb, struct fid *fid,
int fh_len, int fh_type)
{
return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
kernfs_fh_get_inode);
}
static struct dentry *kernfs_fh_to_parent(struct super_block *sb, struct fid *fid,
int fh_len, int fh_type)
{
return generic_fh_to_parent(sb, fid, fh_len, fh_type,
kernfs_fh_get_inode);
}
static struct dentry *kernfs_get_parent_dentry(struct dentry *child)
{
struct kernfs_node *kn = kernfs_dentry_node(child);
return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
}
static const struct export_operations kernfs_export_ops = {
.fh_to_dentry = kernfs_fh_to_dentry,
.fh_to_parent = kernfs_fh_to_parent,
.get_parent = kernfs_get_parent_dentry,
};
/**
* kernfs_root_from_sb - determine kernfs_root associated with a super_block
* @sb: the super_block in question
*
* Return the kernfs_root associated with @sb. If @sb is not a kernfs one,
* %NULL is returned.
*/
struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
{
if (sb->s_op == &kernfs_sops)
return kernfs_info(sb)->root;
return NULL;
}
/*
* find the next ancestor in the path down to @child, where @parent was the
* ancestor whose descendant we want to find.
*
* Say the path is /a/b/c/d. @child is d, @parent is NULL. We return the root
* node. If @parent is b, then we return the node for c.
* Passing in d as @parent is not ok.
*/
static struct kernfs_node *find_next_ancestor(struct kernfs_node *child,
struct kernfs_node *parent)
{
if (child == parent) {
pr_crit_once("BUG in find_next_ancestor: called with parent == child");
return NULL;
}
while (child->parent != parent) {
if (!child->parent)
return NULL;
child = child->parent;
}
return child;
}
/**
* kernfs_node_dentry - get a dentry for the given kernfs_node
* @kn: kernfs_node for which a dentry is needed
* @sb: the kernfs super_block
*/
struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
struct super_block *sb)
{
struct dentry *dentry;
struct kernfs_node *knparent = NULL;
BUG_ON(sb->s_op != &kernfs_sops);
dentry = dget(sb->s_root);
/* Check if this is the root kernfs_node */
if (!kn->parent)
return dentry;
knparent = find_next_ancestor(kn, NULL);
if (WARN_ON(!knparent)) {
dput(dentry);
return ERR_PTR(-EINVAL);
}
do {
struct dentry *dtmp;
struct kernfs_node *kntmp;
if (kn == knparent)
return dentry;
kntmp = find_next_ancestor(kn, knparent);
if (WARN_ON(!kntmp)) {
dput(dentry);
return ERR_PTR(-EINVAL);
}
dtmp = lookup_one_len_unlocked(kntmp->name, dentry,
strlen(kntmp->name));
dput(dentry);
if (IS_ERR(dtmp))
return dtmp;
knparent = kntmp;
dentry = dtmp;
} while (true);
}
static int kernfs_fill_super(struct super_block *sb, struct kernfs_fs_context *kfc)
{
struct kernfs_super_info *info = kernfs_info(sb);
struct inode *inode;
struct dentry *root;
info->sb = sb;
/* Userspace would break if executables or devices appear on sysfs */
sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
sb->s_blocksize = PAGE_SIZE;
sb->s_blocksize_bits = PAGE_SHIFT;
sb->s_magic = kfc->magic;
sb->s_op = &kernfs_sops;
sb->s_xattr = kernfs_xattr_handlers;
if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP)
sb->s_export_op = &kernfs_export_ops;
sb->s_time_gran = 1;
/* sysfs dentries and inodes don't require IO to create */
sb->s_shrink.seeks = 0;
/* get root inode, initialize and unlock it */
mutex_lock(&kernfs_mutex);
inode = kernfs_get_inode(sb, info->root->kn);
mutex_unlock(&kernfs_mutex);
if (!inode) {
pr_debug("kernfs: could not get root inode\n");
return -ENOMEM;
}
/* instantiate and link root dentry */
root = d_make_root(inode);
if (!root) {
pr_debug("%s: could not get root dentry!\n", __func__);
return -ENOMEM;
}
sb->s_root = root;
sb->s_d_op = &kernfs_dops;
return 0;
}
static int kernfs_test_super(struct super_block *sb, struct fs_context *fc)
{
struct kernfs_super_info *sb_info = kernfs_info(sb);
struct kernfs_super_info *info = fc->s_fs_info;
return sb_info->root == info->root && sb_info->ns == info->ns;
}
static int kernfs_set_super(struct super_block *sb, struct fs_context *fc)
{
struct kernfs_fs_context *kfc = fc->fs_private;
kfc->ns_tag = NULL;
return set_anon_sup
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