[linux-2.6-block.git] / fs / afs / dynroot.c

// SPDX-License-Identifier: GPL-2.0-or-later
/* AFS dynamic root handling
 *
 * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/dns_resolver.h>
#include "internal.h"

const struct file_operations afs_dynroot_file_operations = {
	.open		= dcache_dir_open,
	.release	= dcache_dir_close,
	.iterate_shared	= dcache_readdir,
	.llseek		= dcache_dir_lseek,
};

/*
 * Probe to see if a cell may exist.  This prevents positive dentries from
 * being created unnecessarily.
 */
static int afs_probe_cell_name(struct dentry *dentry)
{
	struct afs_cell *cell;
	struct afs_net *net = afs_d2net(dentry);
	const char *name = dentry->d_name.name;
	size_t len = dentry->d_name.len;
	int ret;

	/* Names prefixed with a dot are R/W mounts. */
	if (name[0] == '.') {
		if (len == 1)
			return -EINVAL;
		name++;
		len--;
	}

	cell = afs_lookup_cell_rcu(net, name, len);
	if (!IS_ERR(cell)) {
		afs_put_cell(net, cell);
		return 0;
	}

	ret = dns_query(net->net, "afsdb", name, len, "srv=1",
			NULL, NULL, false);
	if (ret == -ENODATA)
		ret = -EDESTADDRREQ;
	return ret;
}

/*
 * Try to auto mount the mountpoint with pseudo directory, if the autocell
 * operation is setted.
 */
struct inode *afs_try_auto_mntpt(struct dentry *dentry, struct inode *dir)
{
	struct afs_vnode *vnode = AFS_FS_I(dir);
	struct inode *inode;
	int ret = -ENOENT;

	_enter("%p{%pd}, {%llx:%llu}",
	       dentry, dentry, vnode->fid.vid, vnode->fid.vnode);

	if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
		goto out;

	ret = afs_probe_cell_name(dentry);
	if (ret < 0)
		goto out;

	inode = afs_iget_pseudo_dir(dir->i_sb, false);
	if (IS_ERR(inode)) {
		ret = PTR_ERR(inode);
		goto out;
	}

	_leave("= %p", inode);
	return inode;

out:
	_leave("= %d", ret);
	return ret == -ENOENT ? NULL : ERR_PTR(ret);
}

/*
 * Look up @cell in a dynroot directory.  This is a substitution for the
 * local cell name for the net namespace.
 */
static struct dentry *afs_lookup_atcell(struct dentry *dentry)
{
	struct afs_cell *cell;
	struct afs_net *net = afs_d2net(dentry);
	struct dentry *ret;
	unsigned int seq = 0;
	char *name;
	int len;

	if (!net->ws_cell)
		return ERR_PTR(-ENOENT);

	ret = ERR_PTR(-ENOMEM);
	name = kmalloc(AFS_MAXCELLNAME + 1, GFP_KERNEL);
	if (!name)
		goto out_p;

	rcu_read_lock();
	do {
		read_seqbegin_or_lock(&net->cells_lock, &seq);
		cell = rcu_dereference_raw(net->ws_cell);
		if (cell) {
			len = cell->name_len;
			memcpy(name, cell->name, len + 1);
		}
	} while (need_seqretry(&net->cells_lock, seq));
	done_seqretry(&net->cells_lock, seq);
	rcu_read_unlock();

	ret = ERR_PTR(-ENOENT);
	if (!cell)
		goto out_n;

	ret = lookup_one_len(name, dentry->d_parent, len);

	/* We don't want to d_add() the @cell dentry here as we don't want to
	 * the cached dentry to hide changes to the local cell name.
	 */

out_n:
	kfree(name);
out_p:
	return ret;
}

/*
 * Look up an entry in a dynroot directory.
 */
static struct dentry *afs_dynroot_lookup(struct inode *dir, struct dentry *dentry,
					 unsigned int flags)
{
	_enter("%pd", dentry);

	ASSERTCMP(d_inode(dentry), ==, NULL);

	if (dentry->d_name.len >= AFSNAMEMAX) {
		_leave(" = -ENAMETOOLONG");
		return ERR_PTR(-ENAMETOOLONG);
	}

	if (dentry->d_name.len == 5 &&
	    memcmp(dentry->d_name.name, "@cell", 5) == 0)
		return afs_lookup_atcell(dentry);

	return d_splice_alias(afs_try_auto_mntpt(dentry, dir), dentry);
}

const struct inode_operations afs_dynroot_inode_operations = {
	.lookup		= afs_dynroot_lookup,
};

/*
 * Dirs in the dynamic root don't need revalidation.
 */
static int afs_dynroot_d_revalidate(struct dentry *dentry, unsigned int flags)
{
	return 1;
}

/*
 * Allow the VFS to enquire as to whether a dentry should be unhashed (mustn't
 * sleep)
 * - called from dput() when d_count is going to 0.
 * - return 1 to request dentry be unhashed, 0 otherwise
 */
static int afs_dynroot_d_delete(const struct dentry *dentry)
{
	return d_really_is_positive(dentry);
}

const struct dentry_operations afs_dynroot_dentry_operations = {
	.d_revalidate	= afs_dynroot_d_revalidate,
	.d_delete	= afs_dynroot_d_delete,
	.d_release	= afs_d_release,
	.d_automount	= afs_d_automount,
};

/*
 * Create a manually added cell mount directory.
 * - The caller must hold net->proc_cells_lock
 */
int afs_dynroot_mkdir(struct afs_net *net, struct afs_cell *cell)
{
	struct super_block *sb = net->dynroot_sb;
	struct dentry *root, *subdir;
	int ret;

	if (!sb || atomic_read(&sb->s_active) == 0)
		return 0;

	/* Let the ->lookup op do the creation */
	root = sb->s_root;
	inode_lock(root->d_inode);
	subdir = lookup_one_len(cell->name, root, cell->name_len);
	if (IS_ERR(subdir)) {
		ret = PTR_ERR(subdir);
		goto unlock;
	}

	/* Note that we're retaining an extra ref on the dentry */
	subdir->d_fsdata = (void *)1UL;
	ret = 0;
unlock:
	inode_unlock(root->d_inode);
	return ret;
}

/*
 * Remove a manually added cell mount directory.
 * - The caller must hold net->proc_cells_lock
 */
void afs_dynroot_rmdir(struct afs_net *net, struct afs_cell *cell)
{
	struct super_block *sb = net->dynroot_sb;
	struct dentry *root, *subdir;

	if (!sb || atomic_read(&sb->s_active) == 0)
		return;

	root = sb->s_root;
	inode_lock(root->d_inode);

	/* Don't want to trigger a lookup call, which will re-add the cell */
	subdir = try_lookup_one_len(cell->name, root, cell->name_len);
	if (IS_ERR_OR_NULL(subdir)) {
		_debug("lookup %ld", PTR_ERR(subdir));
		goto no_dentry;
	}

	_debug("rmdir %pd %u", subdir, d_count(subdir));

	if (subdir->d_fsdata) {
		_debug("unpin %u", d_count(subdir));
		subdir->d_fsdata = NULL;
		dput(subdir);
	}
	dput(subdir);
no_dentry:
	inode_unlock(root->d_inode);
	_leave("");
}

/*
 * Populate a newly created dynamic root with cell names.
 */
int afs_dynroot_populate(struct super_block *sb)
{
	struct afs_cell *cell;
	struct afs_net *net = afs_sb2net(sb);
	int ret;

	mutex_lock(&net->proc_cells_lock);

	net->dynroot_sb = sb;
	hlist_for_each_entry(cell, &net->proc_cells, proc_link) {
		ret = afs_dynroot_mkdir(net, cell);
		if (ret < 0)
			goto error;
	}

	ret = 0;
out:
	mutex_unlock(&net->proc_cells_lock);
	return ret;

error:
	net->dynroot_sb = NULL;
	goto out;
}

/*
 * When a dynamic root that's in the process of being destroyed, depopulate it
 * of pinned directories.
 */
void afs_dynroot_depopulate(struct super_block *sb)
{
	struct afs_net *net = afs_sb2net(sb);
	struct dentry *root = sb->s_root, *subdir, *tmp;

	/* Prevent more subdirs from being created */
	mutex_lock(&net->proc_cells_lock);
	if (net->dynroot_sb == sb)
		net->dynroot_sb = NULL;
	mutex_unlock(&net->proc_cells_lock);

	inode_lock(root->d_inode);

	/* Remove all the pins for dirs created for manually added cells */
	list_for_each_entry_safe(subdir, tmp, &root->d_subdirs, d_child) {
		if (subdir->d_fsdata) {
			subdir->d_fsdata = NULL;
			dput(subdir);
		}
	}

	inode_unlock(root->d_inode);
}
Commit	Line	Data
b4d0d230	1	// SPDX-License-Identifier: GPL-2.0-or-later
0da0b7fd	2	/* AFS dynamic root handling
66c7e1d3 DH	3	*
	4	* Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
	5	* Written by David Howells (dhowells@redhat.com)
66c7e1d3 DH	6	*/
	7
	8	#include <linux/fs.h>
	9	#include <linux/namei.h>
	10	#include <linux/dns_resolver.h>
	11	#include "internal.h"
	12
	13	const struct file_operations afs_dynroot_file_operations = {
	14	.open = dcache_dir_open,
	15	.release = dcache_dir_close,
	16	.iterate_shared = dcache_readdir,
	17	.llseek = dcache_dir_lseek,
	18	};
	19
	20	/*
	21	* Probe to see if a cell may exist. This prevents positive dentries from
	22	* being created unnecessarily.
	23	*/
	24	static int afs_probe_cell_name(struct dentry *dentry)
	25	{
	26	struct afs_cell *cell;
a58946c1	27	struct afs_net *net = afs_d2net(dentry);
66c7e1d3 DH	28	const char *name = dentry->d_name.name;
	29	size_t len = dentry->d_name.len;
	30	int ret;
	31
	32	/* Names prefixed with a dot are R/W mounts. */
	33	if (name[0] == '.') {
	34	if (len == 1)
	35	return -EINVAL;
	36	name++;
	37	len--;
	38	}
	39
a58946c1	40	cell = afs_lookup_cell_rcu(net, name, len);
66c7e1d3	41	if (!IS_ERR(cell)) {
a58946c1	42	afs_put_cell(net, cell);
66c7e1d3 DH	43	return 0;
	44	}
	45
a58946c1 DH	46	ret = dns_query(net->net, "afsdb", name, len, "srv=1",
a58946c1 DH	47	NULL, NULL, false);
66c7e1d3 DH	48	if (ret == -ENODATA)
	49	ret = -EDESTADDRREQ;
	50	return ret;
	51	}
	52
	53	/*
	54	* Try to auto mount the mountpoint with pseudo directory, if the autocell
	55	* operation is setted.
	56	*/
	57	struct inode afs_try_auto_mntpt(struct dentry dentry, struct inode *dir)
	58	{
	59	struct afs_vnode *vnode = AFS_FS_I(dir);
	60	struct inode *inode;
	61	int ret = -ENOENT;
	62
3b6492df	63	_enter("%p{%pd}, {%llx:%llu}",
66c7e1d3 DH	64	dentry, dentry, vnode->fid.vid, vnode->fid.vnode);
	65
	66	if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
	67	goto out;
	68
	69	ret = afs_probe_cell_name(dentry);
	70	if (ret < 0)
	71	goto out;
	72
	73	inode = afs_iget_pseudo_dir(dir->i_sb, false);
	74	if (IS_ERR(inode)) {
	75	ret = PTR_ERR(inode);
	76	goto out;
	77	}
	78
	79	_leave("= %p", inode);
	80	return inode;
	81
	82	out:
	83	_leave("= %d", ret);
1401a0fc	84	return ret == -ENOENT ? NULL : ERR_PTR(ret);
66c7e1d3 DH	85	}
	86
	87	/*
	88	* Look up @cell in a dynroot directory. This is a substitution for the
	89	* local cell name for the net namespace.
	90	*/
	91	static struct dentry afs_lookup_atcell(struct dentry dentry)
	92	{
	93	struct afs_cell *cell;
	94	struct afs_net *net = afs_d2net(dentry);
	95	struct dentry *ret;
	96	unsigned int seq = 0;
	97	char *name;
	98	int len;
	99
	100	if (!net->ws_cell)
	101	return ERR_PTR(-ENOENT);
	102
	103	ret = ERR_PTR(-ENOMEM);
	104	name = kmalloc(AFS_MAXCELLNAME + 1, GFP_KERNEL);
	105	if (!name)
	106	goto out_p;
	107
	108	rcu_read_lock();
	109	do {
	110	read_seqbegin_or_lock(&net->cells_lock, &seq);
	111	cell = rcu_dereference_raw(net->ws_cell);
	112	if (cell) {
	113	len = cell->name_len;
	114	memcpy(name, cell->name, len + 1);
	115	}
	116	} while (need_seqretry(&net->cells_lock, seq));
	117	done_seqretry(&net->cells_lock, seq);
	118	rcu_read_unlock();
	119
	120	ret = ERR_PTR(-ENOENT);
	121	if (!cell)
	122	goto out_n;
	123
	124	ret = lookup_one_len(name, dentry->d_parent, len);
	125
	126	/* We don't want to d_add() the @cell dentry here as we don't want to
	127	* the cached dentry to hide changes to the local cell name.
	128	*/
	129
	130	out_n:
	131	kfree(name);
	132	out_p:
	133	return ret;
	134	}
	135
	136	/*
	137	* Look up an entry in a dynroot directory.
	138	*/
	139	static struct dentry afs_dynroot_lookup(struct inode dir, struct dentry *dentry,
	140	unsigned int flags)
	141	{
66c7e1d3 DH	142	_enter("%pd", dentry);
	143
	144	ASSERTCMP(d_inode(dentry), ==, NULL);
	145
	146	if (dentry->d_name.len >= AFSNAMEMAX) {
	147	_leave(" = -ENAMETOOLONG");
	148	return ERR_PTR(-ENAMETOOLONG);
	149	}
	150
	151	if (dentry->d_name.len == 5 &&
	152	memcmp(dentry->d_name.name, "@cell", 5) == 0)
	153	return afs_lookup_atcell(dentry);
	154
1401a0fc	155	return d_splice_alias(afs_try_auto_mntpt(dentry, dir), dentry);
66c7e1d3 DH	156	}
	157
	158	const struct inode_operations afs_dynroot_inode_operations = {
	159	.lookup = afs_dynroot_lookup,
	160	};
	161
	162	/*
	163	* Dirs in the dynamic root don't need revalidation.
	164	*/
	165	static int afs_dynroot_d_revalidate(struct dentry *dentry, unsigned int flags)
	166	{
	167	return 1;
	168	}
	169
	170	/*
	171	* Allow the VFS to enquire as to whether a dentry should be unhashed (mustn't
	172	* sleep)
	173	* - called from dput() when d_count is going to 0.
	174	* - return 1 to request dentry be unhashed, 0 otherwise
	175	*/
	176	static int afs_dynroot_d_delete(const struct dentry *dentry)
	177	{
	178	return d_really_is_positive(dentry);
	179	}
	180
	181	const struct dentry_operations afs_dynroot_dentry_operations = {
	182	.d_revalidate = afs_dynroot_d_revalidate,
	183	.d_delete = afs_dynroot_d_delete,
	184	.d_release = afs_d_release,
	185	.d_automount = afs_d_automount,
	186	};
0da0b7fd DH	187
	188	/*
	189	* Create a manually added cell mount directory.
	190	* - The caller must hold net->proc_cells_lock
	191	*/
	192	int afs_dynroot_mkdir(struct afs_net net, struct afs_cell cell)
	193	{
	194	struct super_block *sb = net->dynroot_sb;
	195	struct dentry root, subdir;
	196	int ret;
	197
	198	if (!sb \|\| atomic_read(&sb->s_active) == 0)
	199	return 0;
	200
	201	/* Let the ->lookup op do the creation */
	202	root = sb->s_root;
	203	inode_lock(root->d_inode);
	204	subdir = lookup_one_len(cell->name, root, cell->name_len);
	205	if (IS_ERR(subdir)) {
	206	ret = PTR_ERR(subdir);
	207	goto unlock;
	208	}
	209
	210	/* Note that we're retaining an extra ref on the dentry */
	211	subdir->d_fsdata = (void *)1UL;
	212	ret = 0;
	213	unlock:
	214	inode_unlock(root->d_inode);
	215	return ret;
	216	}
	217
	218	/*
	219	* Remove a manually added cell mount directory.
	220	* - The caller must hold net->proc_cells_lock
	221	*/
	222	void afs_dynroot_rmdir(struct afs_net net, struct afs_cell cell)
	223	{
	224	struct super_block *sb = net->dynroot_sb;
	225	struct dentry root, subdir;
	226
	227	if (!sb \|\| atomic_read(&sb->s_active) == 0)
	228	return;
	229
	230	root = sb->s_root;
	231	inode_lock(root->d_inode);
	232
	233	/* Don't want to trigger a lookup call, which will re-add the cell */
	234	subdir = try_lookup_one_len(cell->name, root, cell->name_len);
	235	if (IS_ERR_OR_NULL(subdir)) {
	236	_debug("lookup %ld", PTR_ERR(subdir));
	237	goto no_dentry;
	238	}
	239
	240	_debug("rmdir %pd %u", subdir, d_count(subdir));
	241
	242	if (subdir->d_fsdata) {
	243	_debug("unpin %u", d_count(subdir));
	244	subdir->d_fsdata = NULL;
	245	dput(subdir);
	246	}
	247	dput(subdir);
	248	no_dentry:
	249	inode_unlock(root->d_inode);
	250	_leave("");
251	}
252
253	/*
254	* Populate a newly created dynamic root with cell names.
255	*/
256	int afs_dynroot_populate(struct super_block *sb)
257	{
258	struct afs_cell *cell;
259	struct afs_net *net = afs_sb2net(sb);
260	int ret;
261
3b05e528	262	mutex_lock(&net->proc_cells_lock);
0da0b7fd DH	263
0da0b7fd DH	264	net->dynroot_sb = sb;
6b3944e4	265	hlist_for_each_entry(cell, &net->proc_cells, proc_link) {
0da0b7fd DH	266	ret = afs_dynroot_mkdir(net, cell);
	267	if (ret < 0)
	268	goto error;
	269	}
	270
	271	ret = 0;
	272	out:
	273	mutex_unlock(&net->proc_cells_lock);
	274	return ret;
	275
	276	error:
	277	net->dynroot_sb = NULL;
	278	goto out;
	279	}
	280
	281	/*
	282	* When a dynamic root that's in the process of being destroyed, depopulate it
	283	* of pinned directories.
	284	*/
	285	void afs_dynroot_depopulate(struct super_block *sb)
	286	{
	287	struct afs_net *net = afs_sb2net(sb);
	288	struct dentry root = sb->s_root, subdir, *tmp;
	289
	290	/* Prevent more subdirs from being created */
	291	mutex_lock(&net->proc_cells_lock);
	292	if (net->dynroot_sb == sb)
	293	net->dynroot_sb = NULL;
	294	mutex_unlock(&net->proc_cells_lock);
	295
	296	inode_lock(root->d_inode);
	297
	298	/* Remove all the pins for dirs created for manually added cells */
	299	list_for_each_entry_safe(subdir, tmp, &root->d_subdirs, d_child) {
	300	if (subdir->d_fsdata) {
	301	subdir->d_fsdata = NULL;
	302	dput(subdir);
	303	}
	304	}
	305
	306	inode_unlock(root->d_inode);
	307	}