/usr/src/aufs-4.9+20161219/fs/aufs/sysfs.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/>.
*/
/*
* sysfs interface
*/
#include <linux/compat.h>
#include <linux/seq_file.h>
#include "aufs.h"
#ifdef CONFIG_AUFS_FS_MODULE
/* this entry violates the "one line per file" policy of sysfs */
static ssize_t config_show(struct kobject *kobj, struct kobj_attribute *attr,
char *buf)
{
ssize_t err;
static char *conf =
/* this file is generated at compiling */
#include "conf.str"
;
err = snprintf(buf, PAGE_SIZE, conf);
if (unlikely(err >= PAGE_SIZE))
err = -EFBIG;
return err;
}
static struct kobj_attribute au_config_attr = __ATTR_RO(config);
#endif
static struct attribute *au_attr[] = {
#ifdef CONFIG_AUFS_FS_MODULE
&au_config_attr.attr,
#endif
NULL, /* need to NULL terminate the list of attributes */
};
static struct attribute_group sysaufs_attr_group_body = {
.attrs = au_attr
};
struct attribute_group *sysaufs_attr_group = &sysaufs_attr_group_body;
/* ---------------------------------------------------------------------- */
int sysaufs_si_xi_path(struct seq_file *seq, struct super_block *sb)
{
int err;
SiMustAnyLock(sb);
err = 0;
if (au_opt_test(au_mntflags(sb), XINO)) {
err = au_xino_path(seq, au_sbi(sb)->si_xib);
seq_putc(seq, '\n');
}
return err;
}
/*
* the lifetime of branch is independent from the entry under sysfs.
* sysfs handles the lifetime of the entry, and never call ->show() after it is
* unlinked.
*/
static int sysaufs_si_br(struct seq_file *seq, struct super_block *sb,
aufs_bindex_t bindex, int idx)
{
int err;
struct path path;
struct dentry *root;
struct au_branch *br;
au_br_perm_str_t perm;
AuDbg("b%d\n", bindex);
err = 0;
root = sb->s_root;
di_read_lock_parent(root, !AuLock_IR);
br = au_sbr(sb, bindex);
switch (idx) {
case AuBrSysfs_BR:
path.mnt = au_br_mnt(br);
path.dentry = au_h_dptr(root, bindex);
err = au_seq_path(seq, &path);
if (!err) {
au_optstr_br_perm(&perm, br->br_perm);
seq_printf(seq, "=%s\n", perm.a);
}
break;
case AuBrSysfs_BRID:
seq_printf(seq, "%d\n", br->br_id);
break;
}
di_read_unlock(root, !AuLock_IR);
if (unlikely(err || seq_has_overflowed(seq)))
err = -E2BIG;
return err;
}
/* ---------------------------------------------------------------------- */
static struct seq_file *au_seq(char *p, ssize_t len)
{
struct seq_file *seq;
seq = kzalloc(sizeof(*seq), GFP_NOFS);
if (seq) {
/* mutex_init(&seq.lock); */
seq->buf = p;
seq->size = len;
return seq; /* success */
}
seq = ERR_PTR(-ENOMEM);
return seq;
}
#define SysaufsBr_PREFIX "br"
#define SysaufsBrid_PREFIX "brid"
/* todo: file size may exceed PAGE_SIZE */
ssize_t sysaufs_si_show(struct kobject *kobj, struct attribute *attr,
char *buf)
{
ssize_t err;
int idx;
long l;
aufs_bindex_t bbot;
struct au_sbinfo *sbinfo;
struct super_block *sb;
struct seq_file *seq;
char *name;
struct attribute **cattr;
sbinfo = container_of(kobj, struct au_sbinfo, si_kobj);
sb = sbinfo->si_sb;
/*
* prevent a race condition between sysfs and aufs.
* for instance, sysfs_file_read() calls sysfs_get_active_two() which
* prohibits maintaining the sysfs entries.
* hew we acquire read lock after sysfs_get_active_two().
* on the other hand, the remount process may maintain the sysfs/aufs
* entries after acquiring write lock.
* it can cause a deadlock.
* simply we gave up processing read here.
*/
err = -EBUSY;
if (unlikely(!si_noflush_read_trylock(sb)))
goto out;
seq = au_seq(buf, PAGE_SIZE);
err = PTR_ERR(seq);
if (IS_ERR(seq))
goto out_unlock;
name = (void *)attr->name;
cattr = sysaufs_si_attrs;
while (*cattr) {
if (!strcmp(name, (*cattr)->name)) {
err = container_of(*cattr, struct sysaufs_si_attr, attr)
->show(seq, sb);
goto out_seq;
}
cattr++;
}
if (!strncmp(name, SysaufsBrid_PREFIX,
sizeof(SysaufsBrid_PREFIX) - 1)) {
idx = AuBrSysfs_BRID;
name += sizeof(SysaufsBrid_PREFIX) - 1;
} else if (!strncmp(name, SysaufsBr_PREFIX,
sizeof(SysaufsBr_PREFIX) - 1)) {
idx = AuBrSysfs_BR;
name += sizeof(SysaufsBr_PREFIX) - 1;
} else
BUG();
err = kstrtol(name, 10, &l);
if (!err) {
bbot = au_sbbot(sb);
if (l <= bbot)
err = sysaufs_si_br(seq, sb, (aufs_bindex_t)l, idx);
else
err = -ENOENT;
}
out_seq:
if (!err) {
err = seq->count;
/* sysfs limit */
if (unlikely(err == PAGE_SIZE))
err = -EFBIG;
}
au_delayed_kfree(seq);
out_unlock:
si_read_unlock(sb);
out:
return err;
}
/* ---------------------------------------------------------------------- */
static int au_brinfo(struct super_block *sb, union aufs_brinfo __user *arg)
{
int err;
int16_t brid;
aufs_bindex_t bindex, bbot;
size_t sz;
char *buf;
struct seq_file *seq;
struct au_branch *br;
si_read_lock(sb, AuLock_FLUSH);
bbot = au_sbbot(sb);
err = bbot + 1;
if (!arg)
goto out;
err = -ENOMEM;
buf = (void *)__get_free_page(GFP_NOFS);
if (unlikely(!buf))
goto out;
seq = au_seq(buf, PAGE_SIZE);
err = PTR_ERR(seq);
if (IS_ERR(seq))
goto out_buf;
sz = sizeof(*arg) - offsetof(union aufs_brinfo, path);
for (bindex = 0; bindex <= bbot; bindex++, arg++) {
err = !access_ok(VERIFY_WRITE, arg, sizeof(*arg));
if (unlikely(err))
break;
br = au_sbr(sb, bindex);
brid = br->br_id;
BUILD_BUG_ON(sizeof(brid) != sizeof(arg->id));
err = __put_user(brid, &arg->id);
if (unlikely(err))
break;
BUILD_BUG_ON(sizeof(br->br_perm) != sizeof(arg->perm));
err = __put_user(br->br_perm, &arg->perm);
if (unlikely(err))
break;
err = au_seq_path(seq, &br->br_path);
if (unlikely(err))
break;
seq_putc(seq, '\0');
if (!seq_has_overflowed(seq)) {
err = copy_to_user(arg->path, seq->buf, seq->count);
seq->count = 0;
if (unlikely(err))
break;
} else {
err = -E2BIG;
goto out_seq;
}
}
if (unlikely(err))
err = -EFAULT;
out_seq:
au_delayed_kfree(seq);
out_buf:
au_delayed_free_page((unsigned long)buf);
out:
si_read_unlock(sb);
return err;
}
long au_brinfo_ioctl(struct file *file, unsigned long arg)
{
return au_brinfo(file->f_path.dentry->d_sb, (void __user *)arg);
}
#ifdef CONFIG_COMPAT
long au_brinfo_compat_ioctl(struct file *file, unsigned long arg)
{
return au_brinfo(file->f_path.dentry->d_sb, compat_ptr(arg));
}
#endif
/* ---------------------------------------------------------------------- */
void sysaufs_br_init(struct au_branch *br)
{
int i;
struct au_brsysfs *br_sysfs;
struct attribute *attr;
br_sysfs = br->br_sysfs;
for (i = 0; i < ARRAY_SIZE(br->br_sysfs); i++) {
attr = &br_sysfs->attr;
sysfs_attr_init(attr);
attr->name = br_sysfs->name;
attr->mode = S_IRUGO;
br_sysfs++;
}
}
void sysaufs_brs_del(struct super_block *sb, aufs_bindex_t bindex)
{
struct au_branch *br;
struct kobject *kobj;
struct au_brsysfs *br_sysfs;
int i;
aufs_bindex_t bbot;
dbgaufs_brs_del(sb, bindex);
if (!sysaufs_brs)
return;
kobj = &au_sbi(sb)->si_kobj;
bbot = au_sbbot(sb);
for (; bindex <= bbot; bindex++) {
br = au_sbr(sb, bindex);
br_sysfs = br->br_sysfs;
for (i = 0; i < ARRAY_SIZE(br->br_sysfs); i++) {
sysfs_remove_file(kobj, &br_sysfs->attr);
br_sysfs++;
}
}
}
void sysaufs_brs_add(struct super_block *sb, aufs_bindex_t bindex)
{
int err, i;
aufs_bindex_t bbot;
struct kobject *kobj;
struct au_branch *br;
struct au_brsysfs *br_sysfs;
dbgaufs_brs_add(sb, bindex);
if (!sysaufs_brs)
return;
kobj = &au_sbi(sb)->si_kobj;
bbot = au_sbbot(sb);
for (; bindex <= bbot; bindex++) {
br = au_sbr(sb, bindex);
br_sysfs = br->br_sysfs;
snprintf(br_sysfs[AuBrSysfs_BR].name, sizeof(br_sysfs->name),
SysaufsBr_PREFIX "%d", bindex);
snprintf(br_sysfs[AuBrSysfs_BRID].name, sizeof(br_sysfs->name),
SysaufsBrid_PREFIX "%d", bindex);
for (i = 0; i < ARRAY_SIZE(br->br_sysfs); i++) {
err = sysfs_create_file(kobj, &br_sysfs->attr);
if (unlikely(err))
pr_warn("failed %s under sysfs(%d)\n",
br_sysfs->name, err);
br_sysfs++;
}
}
}
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