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linux/fs/autofs4/autofs_i.h
Linus Torvalds 64f371bc31 autofs: make the autofsv5 packet file descriptor use a packetized pipe 
The autofs packet size has had a very unfortunate size problem on x86:
because the alignment of 'u64' differs in 32-bit and 64-bit modes, and
because the packet data was not 8-byte aligned, the size of the autofsv5
packet structure differed between 32-bit and 64-bit modes despite
looking otherwise identical (300 vs 304 bytes respectively).

We first fixed that up by making the 64-bit compat mode know about this
problem in commit a32744d4ab ("autofs: work around unhappy compat
problem on x86-64"), and that made a 32-bit 'systemd' work happily on a
64-bit kernel because everything then worked the same way as on a 32-bit
kernel.

But it turned out that 'automount' had actually known and worked around
this problem in user space, so fixing the kernel to do the proper 32-bit
compatibility handling actually *broke* 32-bit automount on a 64-bit
kernel, because it knew that the packet sizes were wrong and expected
those incorrect sizes.

As a result, we ended up reverting that compatibility mode fix, and
thus breaking systemd again, in commit fcbf94b9de.

With both automount and systemd doing a single read() system call, and
verifying that they get *exactly* the size they expect but using
different sizes, it seemed that fixing one of them inevitably seemed to
break the other.  At one point, a patch I seriously considered applying
from Michael Tokarev did a "strcmp()" to see if it was automount that
was doing the operation.  Ugly, ugly.

However, a prettier solution exists now thanks to the packetized pipe
mode.  By marking the communication pipe as being packetized (by simply
setting the O_DIRECT flag), we can always just write the bigger packet
size, and if user-space does a smaller read, it will just get that
partial end result and the extra alignment padding will simply be thrown
away.

This makes both automount and systemd happy, since they now get the size
they asked for, and the kernel side of autofs simply no longer needs to
care - it could pad out the packet arbitrarily.

Of course, if there is some *other* user of autofs (please, please,
please tell me it ain't so - and we haven't heard of any) that tries to
read the packets with multiple writes, that other user will now be
broken - the whole point of the packetized mode is that one system call
gets exactly one packet, and you cannot read a packet in pieces.

Tested-by: Michael Tokarev <mjt@tls.msk.ru>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: David Miller <davem@davemloft.net>
Cc: Ian Kent <raven@themaw.net>
Cc: Thomas Meyer <thomas@m3y3r.de>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-04-29 13:30:08 -07:00

341 lines
9.2 KiB
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/* -*- c -*- ------------------------------------------------------------- *
*
* linux/fs/autofs/autofs_i.h
*
* Copyright 1997-1998 Transmeta Corporation - All Rights Reserved
* Copyright 2005-2006 Ian Kent <raven@themaw.net>
*
* This file is part of the Linux kernel and is made available under
* the terms of the GNU General Public License, version 2, or at your
* option, any later version, incorporated herein by reference.
*
* ----------------------------------------------------------------------- */
/* Internal header file for autofs */
#include <linux/auto_fs4.h>
#include <linux/auto_dev-ioctl.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <linux/list.h>
/* This is the range of ioctl() numbers we claim as ours */
#define AUTOFS_IOC_FIRST AUTOFS_IOC_READY
#define AUTOFS_IOC_COUNT 32
#define AUTOFS_DEV_IOCTL_IOC_FIRST (AUTOFS_DEV_IOCTL_VERSION)
#define AUTOFS_DEV_IOCTL_IOC_COUNT (AUTOFS_IOC_COUNT - 11)
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/time.h>
#include <linux/string.h>
#include <linux/wait.h>
#include <linux/sched.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <asm/current.h>
#include <asm/uaccess.h>
/* #define DEBUG */
#define DPRINTK(fmt, ...) \
pr_debug("pid %d: %s: " fmt "\n", \
current->pid, __func__, ##__VA_ARGS__)
#define AUTOFS_WARN(fmt, ...) \
printk(KERN_WARNING "pid %d: %s: " fmt "\n", \
current->pid, __func__, ##__VA_ARGS__)
#define AUTOFS_ERROR(fmt, ...) \
printk(KERN_ERR "pid %d: %s: " fmt "\n", \
current->pid, __func__, ##__VA_ARGS__)
/* Unified info structure. This is pointed to by both the dentry and
inode structures. Each file in the filesystem has an instance of this
structure. It holds a reference to the dentry, so dentries are never
flushed while the file exists. All name lookups are dealt with at the
dentry level, although the filesystem can interfere in the validation
process. Readdir is implemented by traversing the dentry lists. */
struct autofs_info {
struct dentry *dentry;
struct inode *inode;
int flags;
struct completion expire_complete;
struct list_head active;
int active_count;
struct list_head expiring;
struct autofs_sb_info *sbi;
unsigned long last_used;
atomic_t count;
uid_t uid;
gid_t gid;
};
#define AUTOFS_INF_EXPIRING (1<<0) /* dentry is in the process of expiring */
#define AUTOFS_INF_PENDING (1<<2) /* dentry pending mount */
struct autofs_wait_queue {
wait_queue_head_t queue;
struct autofs_wait_queue *next;
autofs_wqt_t wait_queue_token;
/* We use the following to see what we are waiting for */
struct qstr name;
u32 dev;
u64 ino;
uid_t uid;
gid_t gid;
pid_t pid;
pid_t tgid;
/* This is for status reporting upon return */
int status;
unsigned int wait_ctr;
};
#define AUTOFS_SBI_MAGIC 0x6d4a556d
struct autofs_sb_info {
u32 magic;
int pipefd;
struct file *pipe;
pid_t oz_pgrp;
int catatonic;
int version;
int sub_version;
int min_proto;
int max_proto;
unsigned long exp_timeout;
unsigned int type;
int reghost_enabled;
int needs_reghost;
struct super_block *sb;
struct mutex wq_mutex;
struct mutex pipe_mutex;
spinlock_t fs_lock;
struct autofs_wait_queue *queues; /* Wait queue pointer */
spinlock_t lookup_lock;
struct list_head active_list;
struct list_head expiring_list;
};
static inline struct autofs_sb_info *autofs4_sbi(struct super_block *sb)
{
return (struct autofs_sb_info *)(sb->s_fs_info);
}
static inline struct autofs_info *autofs4_dentry_ino(struct dentry *dentry)
{
return (struct autofs_info *)(dentry->d_fsdata);
}
/* autofs4_oz_mode(): do we see the man behind the curtain? (The
processes which do manipulations for us in user space sees the raw
filesystem without "magic".) */
static inline int autofs4_oz_mode(struct autofs_sb_info *sbi) {
return sbi->catatonic || task_pgrp_nr(current) == sbi->oz_pgrp;
}
/* Does a dentry have some pending activity? */
static inline int autofs4_ispending(struct dentry *dentry)
{
struct autofs_info *inf = autofs4_dentry_ino(dentry);
if (inf->flags & AUTOFS_INF_PENDING)
return 1;
if (inf->flags & AUTOFS_INF_EXPIRING)
return 1;
return 0;
}
struct inode *autofs4_get_inode(struct super_block *, umode_t);
void autofs4_free_ino(struct autofs_info *);
/* Expiration */
int is_autofs4_dentry(struct dentry *);
int autofs4_expire_wait(struct dentry *dentry);
int autofs4_expire_run(struct super_block *, struct vfsmount *,
struct autofs_sb_info *,
struct autofs_packet_expire __user *);
int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
struct autofs_sb_info *sbi, int when);
int autofs4_expire_multi(struct super_block *, struct vfsmount *,
struct autofs_sb_info *, int __user *);
struct dentry *autofs4_expire_direct(struct super_block *sb,
struct vfsmount *mnt,
struct autofs_sb_info *sbi, int how);
struct dentry *autofs4_expire_indirect(struct super_block *sb,
struct vfsmount *mnt,
struct autofs_sb_info *sbi, int how);
/* Device node initialization */
int autofs_dev_ioctl_init(void);
void autofs_dev_ioctl_exit(void);
/* Operations structures */
extern const struct inode_operations autofs4_symlink_inode_operations;
extern const struct inode_operations autofs4_dir_inode_operations;
extern const struct file_operations autofs4_dir_operations;
extern const struct file_operations autofs4_root_operations;
extern const struct dentry_operations autofs4_dentry_operations;
/* VFS automount flags management functions */
static inline void __managed_dentry_set_automount(struct dentry *dentry)
{
dentry->d_flags |= DCACHE_NEED_AUTOMOUNT;
}
static inline void managed_dentry_set_automount(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
__managed_dentry_set_automount(dentry);
spin_unlock(&dentry->d_lock);
}
static inline void __managed_dentry_clear_automount(struct dentry *dentry)
{
dentry->d_flags &= ~DCACHE_NEED_AUTOMOUNT;
}
static inline void managed_dentry_clear_automount(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
__managed_dentry_clear_automount(dentry);
spin_unlock(&dentry->d_lock);
}
static inline void __managed_dentry_set_transit(struct dentry *dentry)
{
dentry->d_flags |= DCACHE_MANAGE_TRANSIT;
}
static inline void managed_dentry_set_transit(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
__managed_dentry_set_transit(dentry);
spin_unlock(&dentry->d_lock);
}
static inline void __managed_dentry_clear_transit(struct dentry *dentry)
{
dentry->d_flags &= ~DCACHE_MANAGE_TRANSIT;
}
static inline void managed_dentry_clear_transit(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
__managed_dentry_clear_transit(dentry);
spin_unlock(&dentry->d_lock);
}
static inline void __managed_dentry_set_managed(struct dentry *dentry)
{
dentry->d_flags |= (DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT);
}
static inline void managed_dentry_set_managed(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
__managed_dentry_set_managed(dentry);
spin_unlock(&dentry->d_lock);
}
static inline void __managed_dentry_clear_managed(struct dentry *dentry)
{
dentry->d_flags &= ~(DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT);
}
static inline void managed_dentry_clear_managed(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
__managed_dentry_clear_managed(dentry);
spin_unlock(&dentry->d_lock);
}
/* Initializing function */
int autofs4_fill_super(struct super_block *, void *, int);
struct autofs_info *autofs4_new_ino(struct autofs_sb_info *);
void autofs4_clean_ino(struct autofs_info *);
static inline int autofs_prepare_pipe(struct file *pipe)
{
if (!pipe->f_op || !pipe->f_op->write)
return -EINVAL;
if (!S_ISFIFO(pipe->f_dentry->d_inode->i_mode))
return -EINVAL;
/* We want a packet pipe */
pipe->f_flags |= O_DIRECT;
return 0;
}
/* Queue management functions */
int autofs4_wait(struct autofs_sb_info *,struct dentry *, enum autofs_notify);
int autofs4_wait_release(struct autofs_sb_info *,autofs_wqt_t,int);
void autofs4_catatonic_mode(struct autofs_sb_info *);
static inline u32 autofs4_get_dev(struct autofs_sb_info *sbi)
{
return new_encode_dev(sbi->sb->s_dev);
}
static inline u64 autofs4_get_ino(struct autofs_sb_info *sbi)
{
return sbi->sb->s_root->d_inode->i_ino;
}
static inline int simple_positive(struct dentry *dentry)
{
return dentry->d_inode && !d_unhashed(dentry);
}
static inline void __autofs4_add_expiring(struct dentry *dentry)
{
struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
struct autofs_info *ino = autofs4_dentry_ino(dentry);
if (ino) {
if (list_empty(&ino->expiring))
list_add(&ino->expiring, &sbi->expiring_list);
}
return;
}
static inline void autofs4_add_expiring(struct dentry *dentry)
{
struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
struct autofs_info *ino = autofs4_dentry_ino(dentry);
if (ino) {
spin_lock(&sbi->lookup_lock);
if (list_empty(&ino->expiring))
list_add(&ino->expiring, &sbi->expiring_list);
spin_unlock(&sbi->lookup_lock);
}
return;
}
static inline void autofs4_del_expiring(struct dentry *dentry)
{
struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
struct autofs_info *ino = autofs4_dentry_ino(dentry);
if (ino) {
spin_lock(&sbi->lookup_lock);
if (!list_empty(&ino->expiring))
list_del_init(&ino->expiring);
spin_unlock(&sbi->lookup_lock);
}
return;
}
extern void autofs4_kill_sb(struct super_block *);
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