/usr/src/aufs-4.9+20161219/fs/aufs/plink.c is in aufs-dkms 4.9+20161219-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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* Copyright (C) 2005-2016 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);
inode_lock_nested(h_inode, AuLsc_I_CHILD2);
h_dentry = vfsub_lkup_one(tgtname, h_parent);
inode_unlock(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);
}
}
}
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