mntpt.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/* mountpoint management
  3 *
  4 * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
  5 * Written by David Howells (dhowells@redhat.com)
  6 */
  7
  8#include <linux/kernel.h>
  9#include <linux/module.h>
 10#include <linux/init.h>
 11#include <linux/fs.h>
 12#include <linux/pagemap.h>
 13#include <linux/mount.h>
 14#include <linux/namei.h>
 15#include <linux/gfp.h>
 16#include <linux/fs_context.h>
 17#include "internal.h"
 18
 19
 20static struct dentry *afs_mntpt_lookup(struct inode *dir,
 21				       struct dentry *dentry,
 22				       unsigned int flags);
 23static int afs_mntpt_open(struct inode *inode, struct file *file);
 24static void afs_mntpt_expiry_timed_out(struct work_struct *work);
 25
 26const struct file_operations afs_mntpt_file_operations = {
 27	.open		= afs_mntpt_open,
 28	.llseek		= noop_llseek,
 29};
 30
 31const struct inode_operations afs_mntpt_inode_operations = {
 32	.lookup		= afs_mntpt_lookup,
 33	.readlink	= afs_readlink,
 34	.getattr	= afs_getattr,
 35};
 36
 37const struct inode_operations afs_autocell_inode_operations = {
 38	.getattr	= afs_getattr,
 39};
 40
 41static LIST_HEAD(afs_vfsmounts);
 42static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
 43
 44static unsigned long afs_mntpt_expiry_timeout = 10 * 60;
 45
 46static const char afs_root_volume[] = "root.cell";
 47
 48/*
 49 * no valid lookup procedure on this sort of dir
 50 */
 51static struct dentry *afs_mntpt_lookup(struct inode *dir,
 52				       struct dentry *dentry,
 53				       unsigned int flags)
 54{
 55	_enter("%p,%p{%pd2}", dir, dentry, dentry);
 56	return ERR_PTR(-EREMOTE);
 57}
 58
 59/*
 60 * no valid open procedure on this sort of dir
 61 */
 62static int afs_mntpt_open(struct inode *inode, struct file *file)
 63{
 64	_enter("%p,%p{%pD2}", inode, file, file);
 65	return -EREMOTE;
 66}
 67
 68/*
 69 * Set the parameters for the proposed superblock.
 70 */
 71static int afs_mntpt_set_params(struct fs_context *fc, struct dentry *mntpt)
 72{
 73	struct afs_fs_context *ctx = fc->fs_private;
 74	struct afs_super_info *src_as = AFS_FS_S(mntpt->d_sb);
 75	struct afs_vnode *vnode = AFS_FS_I(d_inode(mntpt));
 76	struct afs_cell *cell;
 77	const char *p;
 78	int ret;
 79
 80	if (fc->net_ns != src_as->net_ns) {
 81		put_net(fc->net_ns);
 82		fc->net_ns = get_net(src_as->net_ns);
 83	}
 84
 85	if (src_as->volume && src_as->volume->type == AFSVL_RWVOL) {
 86		ctx->type = AFSVL_RWVOL;
 87		ctx->force = true;
 88	}
 89	if (ctx->cell) {
 90		afs_unuse_cell(ctx->cell, afs_cell_trace_unuse_mntpt);
 91		ctx->cell = NULL;
 92	}
 93	if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
 94		/* if the directory is a pseudo directory, use the d_name */
 95		unsigned size = mntpt->d_name.len;
 96
 97		if (size < 2)
 98			return -ENOENT;
 99
100		p = mntpt->d_name.name;
101		if (mntpt->d_name.name[0] == '.') {
102			size--;
103			p++;
104			ctx->type = AFSVL_RWVOL;
105			ctx->force = true;
106		}
107		if (size > AFS_MAXCELLNAME)
108			return -ENAMETOOLONG;
109
110		cell = afs_lookup_cell(ctx->net, p, size, NULL,
111				       AFS_LOOKUP_CELL_MOUNTPOINT,
112				       afs_cell_trace_use_lookup_mntpt);
113		if (IS_ERR(cell)) {
114			pr_err("kAFS: unable to lookup cell '%pd'\n", mntpt);
115			return PTR_ERR(cell);
116		}
117		ctx->cell = cell;
118
119		ctx->volname = afs_root_volume;
120		ctx->volnamesz = sizeof(afs_root_volume) - 1;
121	} else {
122		/* read the contents of the AFS special symlink */
123		DEFINE_DELAYED_CALL(cleanup);
124		const char *content;
125		loff_t size = i_size_read(d_inode(mntpt));
126
127		if (src_as->cell)
128			ctx->cell = afs_use_cell(src_as->cell, afs_cell_trace_use_mntpt);
129
130		if (size < 2 || size > PAGE_SIZE - 1)
131			return -EINVAL;
132
133		content = afs_get_link(mntpt, d_inode(mntpt), &cleanup);
134		if (IS_ERR(content)) {
135			do_delayed_call(&cleanup);
136			return PTR_ERR(content);
137		}
138
139		ret = -EINVAL;
140		if (content[size - 1] == '.')
141			ret = vfs_parse_fs_qstr(fc, "source",
142						&QSTR_LEN(content, size - 1));
143		do_delayed_call(&cleanup);
144		if (ret < 0)
145			return ret;
146
147		/* Don't cross a backup volume mountpoint from a backup volume */
148		if (src_as->volume && src_as->volume->type == AFSVL_BACKVOL &&
149		    ctx->type == AFSVL_BACKVOL)
150			return -ENODEV;
151	}
152
153	return 0;
154}
155
156/*
157 * create a vfsmount to be automounted
158 */
159static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
160{
161	struct fs_context *fc;
162	struct vfsmount *mnt;
163	int ret;
164
165	BUG_ON(!d_inode(mntpt));
166
167	fc = fs_context_for_submount(&afs_fs_type, mntpt);
168	if (IS_ERR(fc))
169		return ERR_CAST(fc);
170
171	ret = afs_mntpt_set_params(fc, mntpt);
172	if (!ret)
173		mnt = fc_mount(fc);
174	else
175		mnt = ERR_PTR(ret);
176
177	put_fs_context(fc);
178	return mnt;
179}
180
181/*
182 * handle an automount point
183 */
184struct vfsmount *afs_d_automount(struct path *path)
185{
186	struct vfsmount *newmnt;
187
188	_enter("{%pd}", path->dentry);
189
190	newmnt = afs_mntpt_do_automount(path->dentry);
191	if (IS_ERR(newmnt))
192		return newmnt;
193
194	mnt_set_expiry(newmnt, &afs_vfsmounts);
195	queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
196			   afs_mntpt_expiry_timeout * HZ);
197	_leave(" = %p", newmnt);
198	return newmnt;
199}
200
201/*
202 * handle mountpoint expiry timer going off
203 */
204static void afs_mntpt_expiry_timed_out(struct work_struct *work)
205{
206	_enter("");
207
208	if (!list_empty(&afs_vfsmounts)) {
209		mark_mounts_for_expiry(&afs_vfsmounts);
210		queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
211				   afs_mntpt_expiry_timeout * HZ);
212	}
213
214	_leave("");
215}
216
217/*
218 * kill the AFS mountpoint timer if it's still running
219 */
220void afs_mntpt_kill_timer(void)
221{
222	_enter("");
223
224	ASSERT(list_empty(&afs_vfsmounts));
225	cancel_delayed_work_sync(&afs_mntpt_expiry_timer);
226}