[mirror_ubuntu-zesty-kernel.git] / fs / afs / mntpt.c

/* mountpoint management
 *
 * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/mnt_namespace.h>
#include "internal.h"


static struct dentry *afs_mntpt_lookup(struct inode *dir,
				       struct dentry *dentry,
				       struct nameidata *nd);
static int afs_mntpt_open(struct inode *inode, struct file *file);
static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd);
static void afs_mntpt_expiry_timed_out(struct work_struct *work);

const struct file_operations afs_mntpt_file_operations = {
	.open		= afs_mntpt_open,
};

const struct inode_operations afs_mntpt_inode_operations = {
	.lookup		= afs_mntpt_lookup,
	.follow_link	= afs_mntpt_follow_link,
	.readlink	= page_readlink,
	.getattr	= afs_inode_getattr,
};

static LIST_HEAD(afs_vfsmounts);
static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);

unsigned long afs_mntpt_expiry_timeout = 10 * 60;

/*
 * check a symbolic link to see whether it actually encodes a mountpoint
 * - sets the AFS_VNODE_MOUNTPOINT flag on the vnode appropriately
 */
int afs_mntpt_check_symlink(struct afs_vnode *vnode)
{
	struct page *page;
	size_t size;
	char *buf;
	int ret;

	_enter("{%u,%u}", vnode->fid.vnode, vnode->fid.unique);

	/* read the contents of the symlink into the pagecache */
	page = read_mapping_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0, NULL);
	if (IS_ERR(page)) {
		ret = PTR_ERR(page);
		goto out;
	}

	ret = -EIO;
	wait_on_page_locked(page);
	buf = kmap(page);
	if (!PageUptodate(page))
		goto out_free;
	if (PageError(page))
		goto out_free;

	/* examine the symlink's contents */
	size = vnode->status.size;
	_debug("symlink to %*.*s", (int) size, (int) size, buf);

	if (size > 2 &&
	    (buf[0] == '%' || buf[0] == '#') &&
	    buf[size - 1] == '.'
	    ) {
		_debug("symlink is a mountpoint");
		spin_lock(&vnode->lock);
		set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);
		spin_unlock(&vnode->lock);
	}

	ret = 0;

out_free:
	kunmap(page);
	page_cache_release(page);
out:
	_leave(" = %d", ret);
	return ret;
}

/*
 * no valid lookup procedure on this sort of dir
 */
static struct dentry *afs_mntpt_lookup(struct inode *dir,
				       struct dentry *dentry,
				       struct nameidata *nd)
{
	_enter("%p,%p{%p{%s},%s}",
	       dir,
	       dentry,
	       dentry->d_parent,
	       dentry->d_parent ?
	       dentry->d_parent->d_name.name : (const unsigned char *) "",
	       dentry->d_name.name);

	return ERR_PTR(-EREMOTE);
}

/*
 * no valid open procedure on this sort of dir
 */
static int afs_mntpt_open(struct inode *inode, struct file *file)
{
	_enter("%p,%p{%p{%s},%s}",
	       inode, file,
	       file->f_path.dentry->d_parent,
	       file->f_path.dentry->d_parent ?
	       file->f_path.dentry->d_parent->d_name.name :
	       (const unsigned char *) "",
	       file->f_path.dentry->d_name.name);

	return -EREMOTE;
}

/*
 * create a vfsmount to be automounted
 */
static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
{
	struct afs_super_info *super;
	struct vfsmount *mnt;
	struct page *page = NULL;
	size_t size;
	char *buf, *devname = NULL, *options = NULL;
	int ret;

	_enter("{%s}", mntpt->d_name.name);

	BUG_ON(!mntpt->d_inode);

	ret = -EINVAL;
	size = mntpt->d_inode->i_size;
	if (size > PAGE_SIZE - 1)
		goto error;

	ret = -ENOMEM;
	devname = (char *) get_zeroed_page(GFP_KERNEL);
	if (!devname)
		goto error;

	options = (char *) get_zeroed_page(GFP_KERNEL);
	if (!options)
		goto error;

	/* read the contents of the AFS special symlink */
	page = read_mapping_page(mntpt->d_inode->i_mapping, 0, NULL);
	if (IS_ERR(page)) {
		ret = PTR_ERR(page);
		goto error;
	}

	ret = -EIO;
	wait_on_page_locked(page);
	if (!PageUptodate(page) || PageError(page))
		goto error;

	buf = kmap(page);
	memcpy(devname, buf, size);
	kunmap(page);
	page_cache_release(page);
	page = NULL;

	/* work out what options we want */
	super = AFS_FS_S(mntpt->d_sb);
	memcpy(options, "cell=", 5);
	strcpy(options + 5, super->volume->cell->name);
	if (super->volume->type == AFSVL_RWVOL)
		strcat(options, ",rwpath");

	/* try and do the mount */
	_debug("--- attempting mount %s -o %s ---", devname, options);
	mnt = vfs_kern_mount(&afs_fs_type, 0, devname, options);
	_debug("--- mount result %p ---", mnt);

	free_page((unsigned long) devname);
	free_page((unsigned long) options);
	_leave(" = %p", mnt);
	return mnt;

error:
	if (page)
		page_cache_release(page);
	if (devname)
		free_page((unsigned long) devname);
	if (options)
		free_page((unsigned long) options);
	_leave(" = %d", ret);
	return ERR_PTR(ret);
}

/*
 * follow a link from a mountpoint directory, thus causing it to be mounted
 */
static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd)
{
	struct vfsmount *newmnt;
	int err;

	_enter("%p{%s},{%s:%p{%s}}",
	       dentry,
	       dentry->d_name.name,
	       nd->mnt->mnt_devname,
	       dentry,
	       nd->dentry->d_name.name);

	dput(nd->dentry);
	nd->dentry = dget(dentry);

	newmnt = afs_mntpt_do_automount(nd->dentry);
	if (IS_ERR(newmnt)) {
		path_release(nd);
		return (void *)newmnt;
	}

	mntget(newmnt);
	err = do_add_mount(newmnt, nd, MNT_SHRINKABLE, &afs_vfsmounts);
	switch (err) {
	case 0:
		path_release(nd);
		nd->mnt = newmnt;
		nd->dentry = dget(newmnt->mnt_root);
		schedule_delayed_work(&afs_mntpt_expiry_timer,
				      afs_mntpt_expiry_timeout * HZ);
		break;
	case -EBUSY:
		/* someone else made a mount here whilst we were busy */
		while (d_mountpoint(nd->dentry) &&
		       follow_down(&nd->mnt, &nd->dentry))
			;
		err = 0;
	default:
		mntput(newmnt);
		break;
	}

	_leave(" = %d", err);
	return ERR_PTR(err);
}

/*
 * handle mountpoint expiry timer going off
 */
static void afs_mntpt_expiry_timed_out(struct work_struct *work)
{
	_enter("");

	if (!list_empty(&afs_vfsmounts)) {
		mark_mounts_for_expiry(&afs_vfsmounts);
		schedule_delayed_work(&afs_mntpt_expiry_timer,
				      afs_mntpt_expiry_timeout * HZ);
	}

	_leave("");
}

/*
 * kill the AFS mountpoint timer if it's still running
 */
void afs_mntpt_kill_timer(void)
{
	_enter("");

	ASSERT(list_empty(&afs_vfsmounts));
	cancel_delayed_work(&afs_mntpt_expiry_timer);
	flush_scheduled_work();
}

/*
 * begin unmount by attempting to remove all automounted mountpoints we added
 */
void afs_umount_begin(struct vfsmount *vfsmnt, int flags)
{
	shrink_submounts(vfsmnt, &afs_vfsmounts);
}
Commit	Line	Data
ec26815a	1	/* mountpoint management
1da177e4 LT	2	*
	3	* Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
	4	* Written by David Howells (dhowells@redhat.com)
	5	*
	6	* This program is free software; you can redistribute it and/or
	7	* modify it under the terms of the GNU General Public License
	8	* as published by the Free Software Foundation; either version
	9	* 2 of the License, or (at your option) any later version.
	10	*/
	11
	12	#include <linux/kernel.h>
	13	#include <linux/module.h>
	14	#include <linux/init.h>
1da177e4 LT	15	#include <linux/slab.h>
	16	#include <linux/fs.h>
	17	#include <linux/pagemap.h>
	18	#include <linux/mount.h>
	19	#include <linux/namei.h>
6b3286ed	20	#include <linux/mnt_namespace.h>
1da177e4 LT	21	#include "internal.h"
	22
	23
	24	static struct dentry afs_mntpt_lookup(struct inode dir,
	25	struct dentry *dentry,
	26	struct nameidata *nd);
	27	static int afs_mntpt_open(struct inode inode, struct file file);
008b150a	28	static void afs_mntpt_follow_link(struct dentry dentry, struct nameidata *nd);
08e0e7c8	29	static void afs_mntpt_expiry_timed_out(struct work_struct *work);
1da177e4	30
4b6f5d20	31	const struct file_operations afs_mntpt_file_operations = {
1da177e4 LT	32	.open = afs_mntpt_open,
	33	};
	34
754661f1	35	const struct inode_operations afs_mntpt_inode_operations = {
1da177e4 LT	36	.lookup = afs_mntpt_lookup,
	37	.follow_link = afs_mntpt_follow_link,
	38	.readlink = page_readlink,
	39	.getattr = afs_inode_getattr,
	40	};
	41
	42	static LIST_HEAD(afs_vfsmounts);
08e0e7c8	43	static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
1da177e4	44
08e0e7c8	45	unsigned long afs_mntpt_expiry_timeout = 10 * 60;
1da177e4	46
1da177e4 LT	47	/*
	48	* check a symbolic link to see whether it actually encodes a mountpoint
	49	* - sets the AFS_VNODE_MOUNTPOINT flag on the vnode appropriately
	50	*/
	51	int afs_mntpt_check_symlink(struct afs_vnode *vnode)
	52	{
	53	struct page *page;
1da177e4 LT	54	size_t size;
	55	char *buf;
	56	int ret;
	57
	58	_enter("{%u,%u}", vnode->fid.vnode, vnode->fid.unique);
	59
	60	/* read the contents of the symlink into the pagecache */
090d2b18	61	page = read_mapping_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0, NULL);
1da177e4 LT	62	if (IS_ERR(page)) {
	63	ret = PTR_ERR(page);
	64	goto out;
	65	}
	66
	67	ret = -EIO;
	68	wait_on_page_locked(page);
	69	buf = kmap(page);
	70	if (!PageUptodate(page))
	71	goto out_free;
	72	if (PageError(page))
	73	goto out_free;
	74
	75	/* examine the symlink's contents */
	76	size = vnode->status.size;
08e0e7c8	77	_debug("symlink to %.s", (int) size, (int) size, buf);
1da177e4 LT	78
	79	if (size > 2 &&
	80	(buf[0] == '%' \|\| buf[0] == '#') &&
	81	buf[size - 1] == '.'
	82	) {
	83	_debug("symlink is a mountpoint");
	84	spin_lock(&vnode->lock);
08e0e7c8	85	set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);
1da177e4 LT	86	spin_unlock(&vnode->lock);
	87	}
	88
	89	ret = 0;
	90
ec26815a	91	out_free:
1da177e4 LT	92	kunmap(page);
1da177e4 LT	93	page_cache_release(page);
ec26815a	94	out:
1da177e4 LT	95	_leave(" = %d", ret);
1da177e4 LT	96	return ret;
ec26815a	97	}
1da177e4	98
1da177e4 LT	99	/*
	100	* no valid lookup procedure on this sort of dir
	101	*/
	102	static struct dentry afs_mntpt_lookup(struct inode dir,
	103	struct dentry *dentry,
	104	struct nameidata *nd)
	105	{
08e0e7c8	106	_enter("%p,%p{%p{%s},%s}",
1da177e4 LT	107	dir,
	108	dentry,
	109	dentry->d_parent,
	110	dentry->d_parent ?
	111	dentry->d_parent->d_name.name : (const unsigned char *) "",
	112	dentry->d_name.name);
	113
	114	return ERR_PTR(-EREMOTE);
ec26815a	115	}
1da177e4	116
1da177e4 LT	117	/*
	118	* no valid open procedure on this sort of dir
	119	*/
	120	static int afs_mntpt_open(struct inode inode, struct file file)
	121	{
08e0e7c8	122	_enter("%p,%p{%p{%s},%s}",
1da177e4	123	inode, file,
1d56a969 JS	124	file->f_path.dentry->d_parent,
	125	file->f_path.dentry->d_parent ?
	126	file->f_path.dentry->d_parent->d_name.name :
1da177e4	127	(const unsigned char *) "",
1d56a969	128	file->f_path.dentry->d_name.name);
1da177e4 LT	129
1da177e4 LT	130	return -EREMOTE;
ec26815a	131	}
1da177e4	132
1da177e4 LT	133	/*
	134	* create a vfsmount to be automounted
	135	*/
	136	static struct vfsmount afs_mntpt_do_automount(struct dentry mntpt)
	137	{
	138	struct afs_super_info *super;
	139	struct vfsmount *mnt;
	140	struct page *page = NULL;
	141	size_t size;
	142	char buf, devname = NULL, *options = NULL;
1da177e4 LT	143	int ret;
1da177e4 LT	144
08e0e7c8	145	_enter("{%s}", mntpt->d_name.name);
1da177e4 LT	146
	147	BUG_ON(!mntpt->d_inode);
	148
	149	ret = -EINVAL;
	150	size = mntpt->d_inode->i_size;
	151	if (size > PAGE_SIZE - 1)
	152	goto error;
	153
	154	ret = -ENOMEM;
	155	devname = (char *) get_zeroed_page(GFP_KERNEL);
	156	if (!devname)
	157	goto error;
	158
	159	options = (char *) get_zeroed_page(GFP_KERNEL);
	160	if (!options)
	161	goto error;
	162
	163	/* read the contents of the AFS special symlink */
090d2b18	164	page = read_mapping_page(mntpt->d_inode->i_mapping, 0, NULL);
1da177e4 LT	165	if (IS_ERR(page)) {
	166	ret = PTR_ERR(page);
	167	goto error;
	168	}
	169
	170	ret = -EIO;
	171	wait_on_page_locked(page);
	172	if (!PageUptodate(page) \|\| PageError(page))
	173	goto error;
	174
	175	buf = kmap(page);
	176	memcpy(devname, buf, size);
	177	kunmap(page);
	178	page_cache_release(page);
	179	page = NULL;
	180
	181	/* work out what options we want */
	182	super = AFS_FS_S(mntpt->d_sb);
	183	memcpy(options, "cell=", 5);
	184	strcpy(options + 5, super->volume->cell->name);
	185	if (super->volume->type == AFSVL_RWVOL)
	186	strcat(options, ",rwpath");
	187
	188	/* try and do the mount */
08e0e7c8	189	_debug("--- attempting mount %s -o %s ---", devname, options);
1f5ce9e9	190	mnt = vfs_kern_mount(&afs_fs_type, 0, devname, options);
08e0e7c8	191	_debug("--- mount result %p ---", mnt);
1da177e4 LT	192
	193	free_page((unsigned long) devname);
	194	free_page((unsigned long) options);
08e0e7c8	195	_leave(" = %p", mnt);
1da177e4 LT	196	return mnt;
1da177e4 LT	197
ec26815a	198	error:
1da177e4 LT	199	if (page)
	200	page_cache_release(page);
	201	if (devname)
	202	free_page((unsigned long) devname);
	203	if (options)
	204	free_page((unsigned long) options);
08e0e7c8	205	_leave(" = %d", ret);
1da177e4	206	return ERR_PTR(ret);
ec26815a	207	}
1da177e4	208
1da177e4 LT	209	/*
	210	* follow a link from a mountpoint directory, thus causing it to be mounted
	211	*/
008b150a	212	static void afs_mntpt_follow_link(struct dentry dentry, struct nameidata *nd)
1da177e4 LT	213	{
1da177e4 LT	214	struct vfsmount *newmnt;
1da177e4 LT	215	int err;
1da177e4 LT	216
08e0e7c8	217	_enter("%p{%s},{%s:%p{%s}}",
1da177e4 LT	218	dentry,
	219	dentry->d_name.name,
	220	nd->mnt->mnt_devname,
	221	dentry,
	222	nd->dentry->d_name.name);
	223
08e0e7c8 DH	224	dput(nd->dentry);
	225	nd->dentry = dget(dentry);
	226
	227	newmnt = afs_mntpt_do_automount(nd->dentry);
1da177e4 LT	228	if (IS_ERR(newmnt)) {
1da177e4 LT	229	path_release(nd);
008b150a	230	return (void *)newmnt;
1da177e4 LT	231	}
1da177e4 LT	232
08e0e7c8 DH	233	mntget(newmnt);
	234	err = do_add_mount(newmnt, nd, MNT_SHRINKABLE, &afs_vfsmounts);
	235	switch (err) {
	236	case 0:
	237	path_release(nd);
1da177e4	238	nd->mnt = newmnt;
08e0e7c8 DH	239	nd->dentry = dget(newmnt->mnt_root);
	240	schedule_delayed_work(&afs_mntpt_expiry_timer,
	241	afs_mntpt_expiry_timeout * HZ);
	242	break;
	243	case -EBUSY:
	244	/* someone else made a mount here whilst we were busy */
	245	while (d_mountpoint(nd->dentry) &&
	246	follow_down(&nd->mnt, &nd->dentry))
	247	;
	248	err = 0;
	249	default:
	250	mntput(newmnt);
	251	break;
1da177e4 LT	252	}
1da177e4 LT	253
08e0e7c8	254	_leave(" = %d", err);
008b150a	255	return ERR_PTR(err);
ec26815a	256	}
1da177e4	257
1da177e4 LT	258	/*
	259	* handle mountpoint expiry timer going off
	260	*/
08e0e7c8	261	static void afs_mntpt_expiry_timed_out(struct work_struct *work)
1da177e4	262	{
08e0e7c8 DH	263	_enter("");
	264
	265	if (!list_empty(&afs_vfsmounts)) {
	266	mark_mounts_for_expiry(&afs_vfsmounts);
	267	schedule_delayed_work(&afs_mntpt_expiry_timer,
	268	afs_mntpt_expiry_timeout * HZ);
	269	}
	270
	271	_leave("");
	272	}
1da177e4	273
08e0e7c8 DH	274	/*
	275	* kill the AFS mountpoint timer if it's still running
	276	*/
	277	void afs_mntpt_kill_timer(void)
	278	{
	279	_enter("");
1da177e4	280
08e0e7c8 DH	281	ASSERT(list_empty(&afs_vfsmounts));
	282	cancel_delayed_work(&afs_mntpt_expiry_timer);
	283	flush_scheduled_work();
	284	}
1da177e4	285
08e0e7c8 DH	286	/*
	287	* begin unmount by attempting to remove all automounted mountpoints we added
	288	*/
	289	void afs_umount_begin(struct vfsmount *vfsmnt, int flags)
	290	{
	291	shrink_submounts(vfsmnt, &afs_vfsmounts);
ec26815a	292	}