linux/fs/autofs/autofs_i.h
Ian Kent 433f9d76a0 autofs: add per dentry expire timeout
Add ability to set per-dentry mount expire timeout to autofs.

There are two fairly well known automounter map formats, the autofs
format and the amd format (more or less System V and Berkley).

Some time ago Linux autofs added an amd map format parser that
implemented a fair amount of the amd functionality. This was done
within the autofs infrastructure and some functionality wasn't
implemented because it either didn't make sense or required extra
kernel changes. The idea was to restrict changes to be within the
existing autofs functionality as much as possible and leave changes
with a wider scope to be considered later.

One of these changes is implementing the amd options:
1) "unmount", expire this mount according to a timeout (same as the
   current autofs default).
2) "nounmount", don't expire this mount (same as setting the autofs
   timeout to 0 except only for this specific mount) .
3) "utimeout=<seconds>", expire this mount using the specified
   timeout (again same as setting the autofs timeout but only for
   this mount).

To implement these options per-dentry expire timeouts need to be
implemented for autofs indirect mounts. This is because all map keys
(mounts) for autofs indirect mounts use an expire timeout stored in
the autofs mount super block info. structure and all indirect mounts
use the same expire timeout.

Now I have a request to add the "nounmount" option so I need to add
the per-dentry expire handling to the kernel implementation to do this.

The implementation uses the trailing path component to identify the
mount (and is also used as the autofs map key) which is passed in the
autofs_dev_ioctl structure path field. The expire timeout is passed
in autofs_dev_ioctl timeout field (well, of the timeout union).

If the passed in timeout is equal to -1 the per-dentry timeout and
flag are cleared providing for the "unmount" option. If the timeout
is greater than or equal to 0 the timeout is set to the value and the
flag is also set. If the dentry timeout is 0 the dentry will not expire
by timeout which enables the implementation of the "nounmount" option
for the specific mount. When the dentry timeout is greater than zero it
allows for the implementation of the "utimeout=<seconds>" option.

Signed-off-by: Ian Kent <raven@themaw.net>
Link: https://lore.kernel.org/r/20240814090231.963520-1-raven@themaw.net
Signed-off-by: Christian Brauner <brauner@kernel.org>
2024-08-30 08:22:36 +02:00

300 lines
8.0 KiB
C

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* Copyright 1997-1998 Transmeta Corporation - All Rights Reserved
* Copyright 2005-2006 Ian Kent <raven@themaw.net>
*/
/* Internal header file for autofs */
#include <linux/auto_fs.h>
#include <linux/auto_dev-ioctl.h>
#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/sched/signal.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/uaccess.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <linux/list.h>
#include <linux/completion.h>
#include <linux/file.h>
#include <linux/magic.h>
#include <linux/fs_context.h>
#include <linux/fs_parser.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_DEV_IOCTL_ISMOUNTPOINT_CMD - AUTOFS_DEV_IOCTL_VERSION_CMD)
#ifdef pr_fmt
#undef pr_fmt
#endif
#define pr_fmt(fmt) KBUILD_MODNAME ":pid:%d:%s: " fmt, current->pid, __func__
extern struct file_system_type autofs_fs_type;
/*
* 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;
int flags;
struct completion expire_complete;
struct list_head active;
struct list_head expiring;
struct autofs_sb_info *sbi;
unsigned long exp_timeout;
unsigned long last_used;
int count;
kuid_t uid;
kgid_t gid;
struct rcu_head rcu;
};
#define AUTOFS_INF_EXPIRING (1<<0) /* dentry in the process of expiring */
#define AUTOFS_INF_WANT_EXPIRE (1<<1) /* the dentry is being considered
* for expiry, so RCU_walk is
* not permitted. If it progresses to
* actual expiry attempt, the flag is
* not cleared when EXPIRING is set -
* in that case it gets cleared only
* when it comes to clearing EXPIRING.
*/
#define AUTOFS_INF_PENDING (1<<2) /* dentry pending mount */
#define AUTOFS_INF_EXPIRE_SET (1<<3) /* per-dentry expire timeout set for
this mount point.
*/
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 offset;
u32 dev;
u64 ino;
kuid_t uid;
kgid_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
#define AUTOFS_SBI_CATATONIC 0x0001
#define AUTOFS_SBI_STRICTEXPIRE 0x0002
#define AUTOFS_SBI_IGNORE 0x0004
struct autofs_sb_info {
u32 magic;
int pipefd;
struct file *pipe;
struct pid *oz_pgrp;
int version;
int sub_version;
int min_proto;
int max_proto;
unsigned int flags;
unsigned long exp_timeout;
unsigned int type;
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;
struct rcu_head rcu;
};
static inline struct autofs_sb_info *autofs_sbi(struct super_block *sb)
{
return (struct autofs_sb_info *)(sb->s_fs_info);
}
static inline struct autofs_info *autofs_dentry_ino(struct dentry *dentry)
{
return (struct autofs_info *)(dentry->d_fsdata);
}
/* autofs_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 autofs_oz_mode(struct autofs_sb_info *sbi)
{
return ((sbi->flags & AUTOFS_SBI_CATATONIC) ||
task_pgrp(current) == sbi->oz_pgrp);
}
static inline bool autofs_empty(struct autofs_info *ino)
{
return ino->count < 2;
}
struct inode *autofs_get_inode(struct super_block *, umode_t);
void autofs_free_ino(struct autofs_info *);
/* Expiration */
int is_autofs_dentry(struct dentry *);
int autofs_expire_wait(const struct path *path, int rcu_walk);
int autofs_expire_run(struct super_block *, struct vfsmount *,
struct autofs_sb_info *,
struct autofs_packet_expire __user *);
int autofs_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
struct autofs_sb_info *sbi, unsigned int how);
int autofs_expire_multi(struct super_block *, struct vfsmount *,
struct autofs_sb_info *, int __user *);
/* Device node initialization */
int autofs_dev_ioctl_init(void);
void autofs_dev_ioctl_exit(void);
/* Operations structures */
extern const struct inode_operations autofs_symlink_inode_operations;
extern const struct inode_operations autofs_dir_inode_operations;
extern const struct file_operations autofs_dir_operations;
extern const struct file_operations autofs_root_operations;
extern const struct dentry_operations autofs_dentry_operations;
/* VFS automount flags management functions */
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 */
extern const struct fs_parameter_spec autofs_param_specs[];
int autofs_init_fs_context(struct fs_context *fc);
struct autofs_info *autofs_new_ino(struct autofs_sb_info *);
void autofs_clean_ino(struct autofs_info *);
static inline int autofs_check_pipe(struct file *pipe)
{
if (!(pipe->f_mode & FMODE_CAN_WRITE))
return -EINVAL;
if (!S_ISFIFO(file_inode(pipe)->i_mode))
return -EINVAL;
return 0;
}
static inline void autofs_set_packet_pipe_flags(struct file *pipe)
{
/* We want a packet pipe */
pipe->f_flags |= O_DIRECT;
/* We don't expect -EAGAIN */
pipe->f_flags &= ~O_NONBLOCK;
}
static inline int autofs_prepare_pipe(struct file *pipe)
{
int ret = autofs_check_pipe(pipe);
if (ret < 0)
return ret;
autofs_set_packet_pipe_flags(pipe);
return 0;
}
/* Queue management functions */
int autofs_wait(struct autofs_sb_info *,
const struct path *, enum autofs_notify);
int autofs_wait_release(struct autofs_sb_info *, autofs_wqt_t, int);
void autofs_catatonic_mode(struct autofs_sb_info *);
static inline u32 autofs_get_dev(struct autofs_sb_info *sbi)
{
return new_encode_dev(sbi->sb->s_dev);
}
static inline u64 autofs_get_ino(struct autofs_sb_info *sbi)
{
return d_inode(sbi->sb->s_root)->i_ino;
}
static inline void __autofs_add_expiring(struct dentry *dentry)
{
struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);
struct autofs_info *ino = autofs_dentry_ino(dentry);
if (ino) {
if (list_empty(&ino->expiring))
list_add(&ino->expiring, &sbi->expiring_list);
}
}
static inline void autofs_add_expiring(struct dentry *dentry)
{
struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);
struct autofs_info *ino = autofs_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);
}
}
static inline void autofs_del_expiring(struct dentry *dentry)
{
struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);
struct autofs_info *ino = autofs_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);
}
}
void autofs_kill_sb(struct super_block *);