[mirror_ubuntu-artful-kernel.git] / fs / aufs / plink.c

/*
 * Copyright (C) 2005-2017 Junjiro R. Okajima
 *
 * This program, aufs 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 * pseudo-link
 */

#include "aufs.h"

/*
 * the pseudo-link maintenance mode.
 * during a user process maintains the pseudo-links,
 * prohibit adding a new plink and branch manipulation.
 *
 * Flags
 * NOPLM:
 *	For entry functions which will handle plink, and i_mutex is already held
 *	in VFS.
 *	They cannot wait and should return an error at once.
 *	Callers has to check the error.
 * NOPLMW:
 *	For entry functions which will handle plink, but i_mutex is not held
 *	in VFS.
 *	They can wait the plink maintenance mode to finish.
 *
 * They behave like F_SETLK and F_SETLKW.
 * If the caller never handle plink, then both flags are unnecessary.
 */

int au_plink_maint(struct super_block *sb, int flags)
{
	int err;
	pid_t pid, ppid;
	struct task_struct *parent, *prev;
	struct au_sbinfo *sbi;

	SiMustAnyLock(sb);

	err = 0;
	if (!au_opt_test(au_mntflags(sb), PLINK))
		goto out;

	sbi = au_sbi(sb);
	pid = sbi->si_plink_maint_pid;
	if (!pid || pid == current->pid)
		goto out;

	/* todo: it highly depends upon /sbin/mount.aufs */
	prev = NULL;
	parent = current;
	ppid = 0;
	rcu_read_lock();
	while (1) {
		parent = rcu_dereference(parent->real_parent);
		if (parent == prev)
			break;
		ppid = task_pid_vnr(parent);
		if (pid == ppid) {
			rcu_read_unlock();
			goto out;
		}
		prev = parent;
	}
	rcu_read_unlock();

	if (au_ftest_lock(flags, NOPLMW)) {
		/* if there is no i_mutex lock in VFS, we don't need to wait */
		/* AuDebugOn(!lockdep_depth(current)); */
		while (sbi->si_plink_maint_pid) {
			si_read_unlock(sb);
			/* gave up wake_up_bit() */
			wait_event(sbi->si_plink_wq, !sbi->si_plink_maint_pid);

			if (au_ftest_lock(flags, FLUSH))
				au_nwt_flush(&sbi->si_nowait);
			si_noflush_read_lock(sb);
		}
	} else if (au_ftest_lock(flags, NOPLM)) {
		AuDbg("ppid %d, pid %d\n", ppid, pid);
		err = -EAGAIN;
	}

out:
	return err;
}

void au_plink_maint_leave(struct au_sbinfo *sbinfo)
{
	spin_lock(&sbinfo->si_plink_maint_lock);
	sbinfo->si_plink_maint_pid = 0;
	spin_unlock(&sbinfo->si_plink_maint_lock);
	wake_up_all(&sbinfo->si_plink_wq);
}

int au_plink_maint_enter(struct super_block *sb)
{
	int err;
	struct au_sbinfo *sbinfo;

	err = 0;
	sbinfo = au_sbi(sb);
	/* make sure i am the only one in this fs */
	si_write_lock(sb, AuLock_FLUSH);
	if (au_opt_test(au_mntflags(sb), PLINK)) {
		spin_lock(&sbinfo->si_plink_maint_lock);
		if (!sbinfo->si_plink_maint_pid)
			sbinfo->si_plink_maint_pid = current->pid;
		else
			err = -EBUSY;
		spin_unlock(&sbinfo->si_plink_maint_lock);
	}
	si_write_unlock(sb);

	return err;
}

/* ---------------------------------------------------------------------- */

#ifdef CONFIG_AUFS_DEBUG
void au_plink_list(struct super_block *sb)
{
	int i;
	struct au_sbinfo *sbinfo;
	struct hlist_head *plink_hlist;
	struct au_icntnr *icntnr;

	SiMustAnyLock(sb);

	sbinfo = au_sbi(sb);
	AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
	AuDebugOn(au_plink_maint(sb, AuLock_NOPLM));

	for (i = 0; i < AuPlink_NHASH; i++) {
		plink_hlist = &sbinfo->si_plink[i].head;
		rcu_read_lock();
		hlist_for_each_entry_rcu(icntnr, plink_hlist, plink)
			AuDbg("%lu\n", icntnr->vfs_inode.i_ino);
		rcu_read_unlock();
	}
}
#endif

/* is the inode pseudo-linked? */
int au_plink_test(struct inode *inode)
{
	int found, i;
	struct au_sbinfo *sbinfo;
	struct hlist_head *plink_hlist;
	struct au_icntnr *icntnr;

	sbinfo = au_sbi(inode->i_sb);
	AuRwMustAnyLock(&sbinfo->si_rwsem);
	AuDebugOn(!au_opt_test(au_mntflags(inode->i_sb), PLINK));
	AuDebugOn(au_plink_maint(inode->i_sb, AuLock_NOPLM));

	found = 0;
	i = au_plink_hash(inode->i_ino);
	plink_hlist = &sbinfo->si_plink[i].head;
	rcu_read_lock();
	hlist_for_each_entry_rcu(icntnr, plink_hlist, plink)
		if (&icntnr->vfs_inode == inode) {
			found = 1;
			break;
		}
	rcu_read_unlock();
	return found;
}

/* ---------------------------------------------------------------------- */

/*
 * generate a name for plink.
 * the file will be stored under AUFS_WH_PLINKDIR.
 */
/* 20 is max digits length of ulong 64 */
#define PLINK_NAME_LEN	((20 + 1) * 2)

static int plink_name(char *name, int len, struct inode *inode,
		      aufs_bindex_t bindex)
{
	int rlen;
	struct inode *h_inode;

	h_inode = au_h_iptr(inode, bindex);
	rlen = snprintf(name, len, "%lu.%lu", inode->i_ino, h_inode->i_ino);
	return rlen;
}

struct au_do_plink_lkup_args {
	struct dentry **errp;
	struct qstr *tgtname;
	struct dentry *h_parent;
	struct au_branch *br;
};

static struct dentry *au_do_plink_lkup(struct qstr *tgtname,
				       struct dentry *h_parent,
				       struct au_branch *br)
{
	struct dentry *h_dentry;
	struct inode *h_inode;

	h_inode = d_inode(h_parent);
	vfsub_inode_lock_shared_nested(h_inode, AuLsc_I_CHILD2);
	h_dentry = vfsub_lkup_one(tgtname, h_parent);
	inode_unlock_shared(h_inode);
	return h_dentry;
}

static void au_call_do_plink_lkup(void *args)
{
	struct au_do_plink_lkup_args *a = args;
	*a->errp = au_do_plink_lkup(a->tgtname, a->h_parent, a->br);
}

/* lookup the plink-ed @inode under the branch at @bindex */
struct dentry *au_plink_lkup(struct inode *inode, aufs_bindex_t bindex)
{
	struct dentry *h_dentry, *h_parent;
	struct au_branch *br;
	int wkq_err;
	char a[PLINK_NAME_LEN];
	struct qstr tgtname = QSTR_INIT(a, 0);

	AuDebugOn(au_plink_maint(inode->i_sb, AuLock_NOPLM));

	br = au_sbr(inode->i_sb, bindex);
	h_parent = br->br_wbr->wbr_plink;
	tgtname.len = plink_name(a, sizeof(a), inode, bindex);

	if (!uid_eq(current_fsuid(), GLOBAL_ROOT_UID)) {
		struct au_do_plink_lkup_args args = {
			.errp		= &h_dentry,
			.tgtname	= &tgtname,
			.h_parent	= h_parent,
			.br		= br
		};

		wkq_err = au_wkq_wait(au_call_do_plink_lkup, &args);
		if (unlikely(wkq_err))
			h_dentry = ERR_PTR(wkq_err);
	} else
		h_dentry = au_do_plink_lkup(&tgtname, h_parent, br);

	return h_dentry;
}

/* create a pseudo-link */
static int do_whplink(struct qstr *tgt, struct dentry *h_parent,
		      struct dentry *h_dentry, struct au_branch *br)
{
	int err;
	struct path h_path = {
		.mnt = au_br_mnt(br)
	};
	struct inode *h_dir, *delegated;

	h_dir = d_inode(h_parent);
	inode_lock_nested(h_dir, AuLsc_I_CHILD2);
again:
	h_path.dentry = vfsub_lkup_one(tgt, h_parent);
	err = PTR_ERR(h_path.dentry);
	if (IS_ERR(h_path.dentry))
		goto out;

	err = 0;
	/* wh.plink dir is not monitored */
	/* todo: is it really safe? */
	if (d_is_positive(h_path.dentry)
	    && d_inode(h_path.dentry) != d_inode(h_dentry)) {
		delegated = NULL;
		err = vfsub_unlink(h_dir, &h_path, &delegated, /*force*/0);
		if (unlikely(err == -EWOULDBLOCK)) {
			pr_warn("cannot retry for NFSv4 delegation"
				" for an internal unlink\n");
			iput(delegated);
		}
		dput(h_path.dentry);
		h_path.dentry = NULL;
		if (!err)
			goto again;
	}
	if (!err && d_is_negative(h_path.dentry)) {
		delegated = NULL;
		err = vfsub_link(h_dentry, h_dir, &h_path, &delegated);
		if (unlikely(err == -EWOULDBLOCK)) {
			pr_warn("cannot retry for NFSv4 delegation"
				" for an internal link\n");
			iput(delegated);
		}
	}
	dput(h_path.dentry);

out:
	inode_unlock(h_dir);
	return err;
}

struct do_whplink_args {
	int *errp;
	struct qstr *tgt;
	struct dentry *h_parent;
	struct dentry *h_dentry;
	struct au_branch *br;
};

static void call_do_whplink(void *args)
{
	struct do_whplink_args *a = args;
	*a->errp = do_whplink(a->tgt, a->h_parent, a->h_dentry, a->br);
}

static int whplink(struct dentry *h_dentry, struct inode *inode,
		   aufs_bindex_t bindex, struct au_branch *br)
{
	int err, wkq_err;
	struct au_wbr *wbr;
	struct dentry *h_parent;
	char a[PLINK_NAME_LEN];
	struct qstr tgtname = QSTR_INIT(a, 0);

	wbr = au_sbr(inode->i_sb, bindex)->br_wbr;
	h_parent = wbr->wbr_plink;
	tgtname.len = plink_name(a, sizeof(a), inode, bindex);

	/* always superio. */
	if (!uid_eq(current_fsuid(), GLOBAL_ROOT_UID)) {
		struct do_whplink_args args = {
			.errp		= &err,
			.tgt		= &tgtname,
			.h_parent	= h_parent,
			.h_dentry	= h_dentry,
			.br		= br
		};
		wkq_err = au_wkq_wait(call_do_whplink, &args);
		if (unlikely(wkq_err))
			err = wkq_err;
	} else
		err = do_whplink(&tgtname, h_parent, h_dentry, br);

	return err;
}

/*
 * create a new pseudo-link for @h_dentry on @bindex.
 * the linked inode is held in aufs @inode.
 */
void au_plink_append(struct inode *inode, aufs_bindex_t bindex,
		     struct dentry *h_dentry)
{
	struct super_block *sb;
	struct au_sbinfo *sbinfo;
	struct hlist_head *plink_hlist;
	struct au_icntnr *icntnr;
	struct au_sphlhead *sphl;
	int found, err, cnt, i;

	sb = inode->i_sb;
	sbinfo = au_sbi(sb);
	AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
	AuDebugOn(au_plink_maint(sb, AuLock_NOPLM));

	found = au_plink_test(inode);
	if (found)
		return;

	i = au_plink_hash(inode->i_ino);
	sphl = sbinfo->si_plink + i;
	plink_hlist = &sphl->head;
	au_igrab(inode);

	spin_lock(&sphl->spin);
	hlist_for_each_entry(icntnr, plink_hlist, plink) {
		if (&icntnr->vfs_inode == inode) {
			found = 1;
			break;
		}
	}
	if (!found) {
		icntnr = container_of(inode, struct au_icntnr, vfs_inode);
		hlist_add_head_rcu(&icntnr->plink, plink_hlist);
	}
	spin_unlock(&sphl->spin);
	if (!found) {
		cnt = au_sphl_count(sphl);
#define msg "unexpectedly unblanced or too many pseudo-links"
		if (cnt > AUFS_PLINK_WARN)
			AuWarn1(msg ", %d\n", cnt);
#undef msg
		err = whplink(h_dentry, inode, bindex, au_sbr(sb, bindex));
		if (unlikely(err)) {
			pr_warn("err %d, damaged pseudo link.\n", err);
			au_sphl_del_rcu(&icntnr->plink, sphl);
			iput(&icntnr->vfs_inode);
		}
	} else
		iput(&icntnr->vfs_inode);
}

/* free all plinks */
void au_plink_put(struct super_block *sb, int verbose)
{
	int i, warned;
	struct au_sbinfo *sbinfo;
	struct hlist_head *plink_hlist;
	struct hlist_node *tmp;
	struct au_icntnr *icntnr;

	SiMustWriteLock(sb);

	sbinfo = au_sbi(sb);
	AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
	AuDebugOn(au_plink_maint(sb, AuLock_NOPLM));

	/* no spin_lock since sbinfo is write-locked */
	warned = 0;
	for (i = 0; i < AuPlink_NHASH; i++) {
		plink_hlist = &sbinfo->si_plink[i].head;
		if (!warned && verbose && !hlist_empty(plink_hlist)) {
			pr_warn("pseudo-link is not flushed");
			warned = 1;
		}
		hlist_for_each_entry_safe(icntnr, tmp, plink_hlist, plink)
			iput(&icntnr->vfs_inode);
		INIT_HLIST_HEAD(plink_hlist);
	}
}

void au_plink_clean(struct super_block *sb, int verbose)
{
	struct dentry *root;

	root = sb->s_root;
	aufs_write_lock(root);
	if (au_opt_test(au_mntflags(sb), PLINK))
		au_plink_put(sb, verbose);
	aufs_write_unlock(root);
}

static int au_plink_do_half_refresh(struct inode *inode, aufs_bindex_t br_id)
{
	int do_put;
	aufs_bindex_t btop, bbot, bindex;

	do_put = 0;
	btop = au_ibtop(inode);
	bbot = au_ibbot(inode);
	if (btop >= 0) {
		for (bindex = btop; bindex <= bbot; bindex++) {
			if (!au_h_iptr(inode, bindex)
			    || au_ii_br_id(inode, bindex) != br_id)
				continue;
			au_set_h_iptr(inode, bindex, NULL, 0);
			do_put = 1;
			break;
		}
		if (do_put)
			for (bindex = btop; bindex <= bbot; bindex++)
				if (au_h_iptr(inode, bindex)) {
					do_put = 0;
					break;
				}
	} else
		do_put = 1;

	return do_put;
}

/* free the plinks on a branch specified by @br_id */
void au_plink_half_refresh(struct super_block *sb, aufs_bindex_t br_id)
{
	struct au_sbinfo *sbinfo;
	struct hlist_head *plink_hlist;
	struct hlist_node *tmp;
	struct au_icntnr *icntnr;
	struct inode *inode;
	int i, do_put;

	SiMustWriteLock(sb);

	sbinfo = au_sbi(sb);
	AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
	AuDebugOn(au_plink_maint(sb, AuLock_NOPLM));

	/* no spin_lock since sbinfo is write-locked */
	for (i = 0; i < AuPlink_NHASH; i++) {
		plink_hlist = &sbinfo->si_plink[i].head;
		hlist_for_each_entry_safe(icntnr, tmp, plink_hlist, plink) {
			inode = au_igrab(&icntnr->vfs_inode);
			ii_write_lock_child(inode);
			do_put = au_plink_do_half_refresh(inode, br_id);
			if (do_put) {
				hlist_del(&icntnr->plink);
				iput(inode);
			}
			ii_write_unlock(inode);
			iput(inode);
		}
	}
}
Commit	Line	Data
b6450630 SF	1	/*
	2	* Copyright (C) 2005-2017 Junjiro R. Okajima
	3	*
	4	* This program, aufs is free software; you can redistribute it and/or modify
	5	* it under the terms of the GNU General Public License as published by
	6	* the Free Software Foundation; either version 2 of the License, or
	7	* (at your option) any later version.
	8	*
	9	* This program is distributed in the hope that it will be useful,
	10	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	11	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	12	* GNU General Public License for more details.
	13	*
	14	* You should have received a copy of the GNU General Public License
	15	* along with this program. If not, see <http://www.gnu.org/licenses/>.
	16	*/
	17
	18	/*
	19	* pseudo-link
	20	*/
	21
	22	#include "aufs.h"
	23
	24	/*
	25	* the pseudo-link maintenance mode.
	26	* during a user process maintains the pseudo-links,
	27	* prohibit adding a new plink and branch manipulation.
	28	*
	29	* Flags
	30	* NOPLM:
	31	* For entry functions which will handle plink, and i_mutex is already held
	32	* in VFS.
	33	* They cannot wait and should return an error at once.
	34	* Callers has to check the error.
	35	* NOPLMW:
	36	* For entry functions which will handle plink, but i_mutex is not held
	37	* in VFS.
	38	* They can wait the plink maintenance mode to finish.
	39	*
	40	* They behave like F_SETLK and F_SETLKW.
	41	* If the caller never handle plink, then both flags are unnecessary.
	42	*/
	43
	44	int au_plink_maint(struct super_block *sb, int flags)
	45	{
	46	int err;
	47	pid_t pid, ppid;
	48	struct task_struct parent, prev;
	49	struct au_sbinfo *sbi;
	50
	51	SiMustAnyLock(sb);
	52
	53	err = 0;
	54	if (!au_opt_test(au_mntflags(sb), PLINK))
	55	goto out;
	56
	57	sbi = au_sbi(sb);
	58	pid = sbi->si_plink_maint_pid;
	59	if (!pid \|\| pid == current->pid)
	60	goto out;
	61
	62	/* todo: it highly depends upon /sbin/mount.aufs */
	63	prev = NULL;
	64	parent = current;
65	ppid = 0;
66	rcu_read_lock();
67	while (1) {
68	parent = rcu_dereference(parent->real_parent);
69	if (parent == prev)
70	break;
71	ppid = task_pid_vnr(parent);
72	if (pid == ppid) {
73	rcu_read_unlock();
74	goto out;
75	}
76	prev = parent;
77	}
78	rcu_read_unlock();
79
80	if (au_ftest_lock(flags, NOPLMW)) {
81	/* if there is no i_mutex lock in VFS, we don't need to wait */
82	/* AuDebugOn(!lockdep_depth(current)); */
83	while (sbi->si_plink_maint_pid) {
84	si_read_unlock(sb);
85	/* gave up wake_up_bit() */
86	wait_event(sbi->si_plink_wq, !sbi->si_plink_maint_pid);
87
88	if (au_ftest_lock(flags, FLUSH))
89	au_nwt_flush(&sbi->si_nowait);
90	si_noflush_read_lock(sb);
91	}
92	} else if (au_ftest_lock(flags, NOPLM)) {
93	AuDbg("ppid %d, pid %d\n", ppid, pid);
94	err = -EAGAIN;
95	}
96
97	out:
98	return err;
99	}
100
101	void au_plink_maint_leave(struct au_sbinfo *sbinfo)
102	{
103	spin_lock(&sbinfo->si_plink_maint_lock);
104	sbinfo->si_plink_maint_pid = 0;
105	spin_unlock(&sbinfo->si_plink_maint_lock);
106	wake_up_all(&sbinfo->si_plink_wq);
107	}
108
109	int au_plink_maint_enter(struct super_block *sb)
110	{
111	int err;
112	struct au_sbinfo *sbinfo;
113
114	err = 0;
115	sbinfo = au_sbi(sb);
116	/* make sure i am the only one in this fs */
117	si_write_lock(sb, AuLock_FLUSH);
118	if (au_opt_test(au_mntflags(sb), PLINK)) {
119	spin_lock(&sbinfo->si_plink_maint_lock);
120	if (!sbinfo->si_plink_maint_pid)
121	sbinfo->si_plink_maint_pid = current->pid;
122	else
123	err = -EBUSY;
124	spin_unlock(&sbinfo->si_plink_maint_lock);
125	}
126	si_write_unlock(sb);
127
128	return err;
129	}
130
131	/* ---------------------------------------------------------------------- */
132
133	#ifdef CONFIG_AUFS_DEBUG
134	void au_plink_list(struct super_block *sb)
135	{
136	int i;
137	struct au_sbinfo *sbinfo;
138	struct hlist_head *plink_hlist;
139	struct au_icntnr *icntnr;
140
141	SiMustAnyLock(sb);
142
143	sbinfo = au_sbi(sb);
144	AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
145	AuDebugOn(au_plink_maint(sb, AuLock_NOPLM));
146
147	for (i = 0; i < AuPlink_NHASH; i++) {
148	plink_hlist = &sbinfo->si_plink[i].head;
149	rcu_read_lock();
150	hlist_for_each_entry_rcu(icntnr, plink_hlist, plink)
151	AuDbg("%lu\n", icntnr->vfs_inode.i_ino);
152	rcu_read_unlock();
153	}
154	}
155	#endif
156
157	/* is the inode pseudo-linked? */
158	int au_plink_test(struct inode *inode)
159	{
160	int found, i;
161	struct au_sbinfo *sbinfo;
162	struct hlist_head *plink_hlist;
163	struct au_icntnr *icntnr;
164
165	sbinfo = au_sbi(inode->i_sb);
166	AuRwMustAnyLock(&sbinfo->si_rwsem);
167	AuDebugOn(!au_opt_test(au_mntflags(inode->i_sb), PLINK));
168	AuDebugOn(au_plink_maint(inode->i_sb, AuLock_NOPLM));
169
170	found = 0;
171	i = au_plink_hash(inode->i_ino);
172	plink_hlist = &sbinfo->si_plink[i].head;
173	rcu_read_lock();
174	hlist_for_each_entry_rcu(icntnr, plink_hlist, plink)
175	if (&icntnr->vfs_inode == inode) {
176	found = 1;
177	break;
178	}
179	rcu_read_unlock();
180	return found;
181	}
182
183	/* ---------------------------------------------------------------------- */
184
185	/*
186	* generate a name for plink.
187	* the file will be stored under AUFS_WH_PLINKDIR.
188	*/
189	/* 20 is max digits length of ulong 64 */
190	#define PLINK_NAME_LEN ((20 + 1) * 2)
191
192	static int plink_name(char name, int len, struct inode inode,
193	aufs_bindex_t bindex)
194	{
195	int rlen;
196	struct inode *h_inode;
197
198	h_inode = au_h_iptr(inode, bindex);
199	rlen = snprintf(name, len, "%lu.%lu", inode->i_ino, h_inode->i_ino);
200	return rlen;
201	}
202
203	struct au_do_plink_lkup_args {
204	struct dentry **errp;
205	struct qstr *tgtname;
206	struct dentry *h_parent;
207	struct au_branch *br;
208	};
209
210	static struct dentry au_do_plink_lkup(struct qstr tgtname,
211	struct dentry *h_parent,
212	struct au_branch *br)
213	{
214	struct dentry *h_dentry;
215	struct inode *h_inode;
216
217	h_inode = d_inode(h_parent);
218	vfsub_inode_lock_shared_nested(h_inode, AuLsc_I_CHILD2);
219	h_dentry = vfsub_lkup_one(tgtname, h_parent);
220	inode_unlock_shared(h_inode);
221	return h_dentry;
222	}
223
224	static void au_call_do_plink_lkup(void *args)
225	{
226	struct au_do_plink_lkup_args *a = args;
227	*a->errp = au_do_plink_lkup(a->tgtname, a->h_parent, a->br);
228	}
229
230	/* lookup the plink-ed @inode under the branch at @bindex */
231	struct dentry au_plink_lkup(struct inode inode, aufs_bindex_t bindex)
232	{
233	struct dentry h_dentry, h_parent;
234	struct au_branch *br;
235	int wkq_err;
236	char a[PLINK_NAME_LEN];
237	struct qstr tgtname = QSTR_INIT(a, 0);
238
239	AuDebugOn(au_plink_maint(inode->i_sb, AuLock_NOPLM));
240
241	br = au_sbr(inode->i_sb, bindex);
242	h_parent = br->br_wbr->wbr_plink;
243	tgtname.len = plink_name(a, sizeof(a), inode, bindex);
244
245	if (!uid_eq(current_fsuid(), GLOBAL_ROOT_UID)) {
246	struct au_do_plink_lkup_args args = {
247	.errp = &h_dentry,
248	.tgtname = &tgtname,
249	.h_parent = h_parent,
250	.br = br
251	};
252
253	wkq_err = au_wkq_wait(au_call_do_plink_lkup, &args);
254	if (unlikely(wkq_err))
255	h_dentry = ERR_PTR(wkq_err);
256	} else
257	h_dentry = au_do_plink_lkup(&tgtname, h_parent, br);
258
259	return h_dentry;
260	}
261
262	/* create a pseudo-link */
263	static int do_whplink(struct qstr tgt, struct dentry h_parent,
264	struct dentry h_dentry, struct au_branch br)
265	{
266	int err;
267	struct path h_path = {
268	.mnt = au_br_mnt(br)
269	};
270	struct inode h_dir, delegated;
271
272	h_dir = d_inode(h_parent);
273	inode_lock_nested(h_dir, AuLsc_I_CHILD2);
274	again:
275	h_path.dentry = vfsub_lkup_one(tgt, h_parent);
276	err = PTR_ERR(h_path.dentry);
277	if (IS_ERR(h_path.dentry))
278	goto out;
279
280	err = 0;
281	/* wh.plink dir is not monitored */
282	/* todo: is it really safe? */
283	if (d_is_positive(h_path.dentry)
284	&& d_inode(h_path.dentry) != d_inode(h_dentry)) {
285	delegated = NULL;
286	err = vfsub_unlink(h_dir, &h_path, &delegated, /force/0);
287	if (unlikely(err == -EWOULDBLOCK)) {
288	pr_warn("cannot retry for NFSv4 delegation"
289	" for an internal unlink\n");
290	iput(delegated);
291	}
292	dput(h_path.dentry);
293	h_path.dentry = NULL;
294	if (!err)
295	goto again;
296	}
297	if (!err && d_is_negative(h_path.dentry)) {
298	delegated = NULL;
299	err = vfsub_link(h_dentry, h_dir, &h_path, &delegated);
300	if (unlikely(err == -EWOULDBLOCK)) {
301	pr_warn("cannot retry for NFSv4 delegation"
302	" for an internal link\n");
303	iput(delegated);
304	}
305	}
306	dput(h_path.dentry);
307
308	out:
309	inode_unlock(h_dir);
310	return err;
311	}
312
313	struct do_whplink_args {
314	int *errp;
315	struct qstr *tgt;
316	struct dentry *h_parent;
317	struct dentry *h_dentry;
318	struct au_branch *br;
319	};
320
321	static void call_do_whplink(void *args)
322	{
323	struct do_whplink_args *a = args;
324	*a->errp = do_whplink(a->tgt, a->h_parent, a->h_dentry, a->br);
325	}
326
327	static int whplink(struct dentry h_dentry, struct inode inode,
328	aufs_bindex_t bindex, struct au_branch *br)
329	{
330	int err, wkq_err;
331	struct au_wbr *wbr;
332	struct dentry *h_parent;
333	char a[PLINK_NAME_LEN];
334	struct qstr tgtname = QSTR_INIT(a, 0);
335
336	wbr = au_sbr(inode->i_sb, bindex)->br_wbr;
337	h_parent = wbr->wbr_plink;
338	tgtname.len = plink_name(a, sizeof(a), inode, bindex);
339
340	/* always superio. */
341	if (!uid_eq(current_fsuid(), GLOBAL_ROOT_UID)) {
342	struct do_whplink_args args = {
343	.errp = &err,
344	.tgt = &tgtname,
345	.h_parent = h_parent,
346	.h_dentry = h_dentry,
347	.br = br
348	};
349	wkq_err = au_wkq_wait(call_do_whplink, &args);
350	if (unlikely(wkq_err))
351	err = wkq_err;
352	} else
353	err = do_whplink(&tgtname, h_parent, h_dentry, br);
354
355	return err;
356	}
357
358	/*
359	* create a new pseudo-link for @h_dentry on @bindex.
360	* the linked inode is held in aufs @inode.
361	*/
362	void au_plink_append(struct inode *inode, aufs_bindex_t bindex,
363	struct dentry *h_dentry)
364	{
365	struct super_block *sb;
366	struct au_sbinfo *sbinfo;
367	struct hlist_head *plink_hlist;
368	struct au_icntnr *icntnr;
369	struct au_sphlhead *sphl;
370	int found, err, cnt, i;
371
372	sb = inode->i_sb;
373	sbinfo = au_sbi(sb);
374	AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
375	AuDebugOn(au_plink_maint(sb, AuLock_NOPLM));
376
377	found = au_plink_test(inode);
378	if (found)
379	return;
380
381	i = au_plink_hash(inode->i_ino);
382	sphl = sbinfo->si_plink + i;
383	plink_hlist = &sphl->head;
384	au_igrab(inode);
385
386	spin_lock(&sphl->spin);
387	hlist_for_each_entry(icntnr, plink_hlist, plink) {
388	if (&icntnr->vfs_inode == inode) {
389	found = 1;
390	break;
391	}
392	}
393	if (!found) {
394	icntnr = container_of(inode, struct au_icntnr, vfs_inode);
395	hlist_add_head_rcu(&icntnr->plink, plink_hlist);
396	}
397	spin_unlock(&sphl->spin);
398	if (!found) {
399	cnt = au_sphl_count(sphl);
400	#define msg "unexpectedly unblanced or too many pseudo-links"
401	if (cnt > AUFS_PLINK_WARN)
402	AuWarn1(msg ", %d\n", cnt);
403	#undef msg
404	err = whplink(h_dentry, inode, bindex, au_sbr(sb, bindex));
405	if (unlikely(err)) {
406	pr_warn("err %d, damaged pseudo link.\n", err);
407	au_sphl_del_rcu(&icntnr->plink, sphl);
408	iput(&icntnr->vfs_inode);
409	}
410	} else
411	iput(&icntnr->vfs_inode);
412	}
413
414	/* free all plinks */
415	void au_plink_put(struct super_block *sb, int verbose)
416	{
417	int i, warned;
418	struct au_sbinfo *sbinfo;
419	struct hlist_head *plink_hlist;
420	struct hlist_node *tmp;
421	struct au_icntnr *icntnr;
422
423	SiMustWriteLock(sb);
424
425	sbinfo = au_sbi(sb);
426	AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
427	AuDebugOn(au_plink_maint(sb, AuLock_NOPLM));
428
429	/* no spin_lock since sbinfo is write-locked */
430	warned = 0;
431	for (i = 0; i < AuPlink_NHASH; i++) {
432	plink_hlist = &sbinfo->si_plink[i].head;
433	if (!warned && verbose && !hlist_empty(plink_hlist)) {
434	pr_warn("pseudo-link is not flushed");
435	warned = 1;
436	}
437	hlist_for_each_entry_safe(icntnr, tmp, plink_hlist, plink)
438	iput(&icntnr->vfs_inode);
439	INIT_HLIST_HEAD(plink_hlist);
440	}
441	}
442
443	void au_plink_clean(struct super_block *sb, int verbose)
444	{
445	struct dentry *root;
446
447	root = sb->s_root;
448	aufs_write_lock(root);
449	if (au_opt_test(au_mntflags(sb), PLINK))
450	au_plink_put(sb, verbose);
451	aufs_write_unlock(root);
452	}
453
454	static int au_plink_do_half_refresh(struct inode *inode, aufs_bindex_t br_id)
455	{
456	int do_put;
457	aufs_bindex_t btop, bbot, bindex;
458
459	do_put = 0;
460	btop = au_ibtop(inode);
461	bbot = au_ibbot(inode);
462	if (btop >= 0) {
463	for (bindex = btop; bindex <= bbot; bindex++) {
464	if (!au_h_iptr(inode, bindex)
465	\|\| au_ii_br_id(inode, bindex) != br_id)
466	continue;
467	au_set_h_iptr(inode, bindex, NULL, 0);
468	do_put = 1;
469	break;
470	}
471	if (do_put)
472	for (bindex = btop; bindex <= bbot; bindex++)
473	if (au_h_iptr(inode, bindex)) {
474	do_put = 0;
475	break;
476	}
477	} else
478	do_put = 1;
479
480	return do_put;
481	}
482
483	/* free the plinks on a branch specified by @br_id */
484	void au_plink_half_refresh(struct super_block *sb, aufs_bindex_t br_id)
485	{
486	struct au_sbinfo *sbinfo;
487	struct hlist_head *plink_hlist;
488	struct hlist_node *tmp;
489	struct au_icntnr *icntnr;
490	struct inode *inode;
491	int i, do_put;
492
493	SiMustWriteLock(sb);
494
495	sbinfo = au_sbi(sb);
496	AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
497	AuDebugOn(au_plink_maint(sb, AuLock_NOPLM));
498
499	/* no spin_lock since sbinfo is write-locked */
500	for (i = 0; i < AuPlink_NHASH; i++) {
501	plink_hlist = &sbinfo->si_plink[i].head;
502	hlist_for_each_entry_safe(icntnr, tmp, plink_hlist, plink) {
503	inode = au_igrab(&icntnr->vfs_inode);
504	ii_write_lock_child(inode);
505	do_put = au_plink_do_half_refresh(inode, br_id);
506	if (do_put) {
507	hlist_del(&icntnr->plink);
508	iput(inode);
509	}
510	ii_write_unlock(inode);
511	iput(inode);
512	}
513	}
514	}