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Commit 8d7b48e0 authored by Ian Kent's avatar Ian Kent Committed by Linus Torvalds
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autofs4: add miscellaneous device for ioctls 



Add a miscellaneous device to the autofs4 module for routing ioctls.  This
provides the ability to obtain an ioctl file handle for an autofs mount
point that is possibly covered by another mount.

The actual problem with autofs is that it can't reconnect to existing
mounts.  Immediately one things of just adding the ability to remount
autofs file systems would solve it, but alas, that can't work.  This is
because autofs direct mounts and the implementation of "on demand mount
and expire" of nested mount trees have the file system mounted on top of
the mount trigger dentry.

To resolve this a miscellaneous device node for routing ioctl commands to
these mount points has been implemented in the autofs4 kernel module and a
library added to autofs.  This provides the ability to open a file
descriptor for these over mounted autofs mount points.

Please refer to Documentation/filesystems/autofs4-mount-control.txt for a
discussion of the problem, implementation alternatives considered and a
description of the interface.

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: build fix]
Signed-off-by: default avatarIan Kent <raven@themaw.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4b22ff13

fs/autofs4/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -4,4 +4,4 @@ 


obj-$(CONFIG_AUTOFS4_FS) += autofs4.o



autofs4-objs := init.o inode.o root.o symlink.o waitq.o expire.o
 
autofs4-objs := init.o inode.o root.o symlink.o waitq.o expire.o dev-ioctl.o

fs/autofs4/autofs_i.h

+33 −2
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
/* Internal header file for autofs */



#include <linux/auto_fs4.h>

#include <linux/auto_dev-ioctl.h>

#include <linux/mutex.h>

#include <linux/list.h>
@@ -21,6 +22,9 @@ 
#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)



#define AUTOFS_TYPE_TRIGGER	(AUTOFS_TYPE_DIRECT|AUTOFS_TYPE_OFFSET)



#include <linux/kernel.h>
@@ -37,11 +41,27 @@ 
/* #define DEBUG */



#ifdef DEBUG

#define DPRINTK(fmt,args...) do { printk(KERN_DEBUG "pid %d: %s: " fmt "\n" , current->pid , __func__ , ##args); } while(0)

#define DPRINTK(fmt, args...)				\

do {							\

	printk(KERN_DEBUG "pid %d: %s: " fmt "\n",	\

		current->pid, __func__, ##args);	\

} while (0)

#else

#define DPRINTK(fmt, args...) do {} while (0)

#endif



#define AUTOFS_WARN(fmt, args...)			\

do {							\

	printk(KERN_WARNING "pid %d: %s: " fmt "\n",	\

		current->pid, __func__, ##args);	\

} while (0)



#define AUTOFS_ERROR(fmt, args...)			\

do {							\

	printk(KERN_ERR "pid %d: %s: " fmt "\n",	\

		current->pid, __func__, ##args);	\

} while (0)



/* 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
@@ -170,6 +190,17 @@ int autofs4_expire_run(struct super_block *, struct vfsmount *, 
			struct autofs_packet_expire __user *);

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 */

fs/autofs4/dev-ioctl.c

0 → 100644
+863 −0

File added.

Preview size limit exceeded, changes collapsed.

fs/autofs4/expire.c

+8 −8
Original line number Diff line number Diff line
@@ -244,7 +244,7 @@ static struct dentry *autofs4_check_leaves(struct vfsmount *mnt, 
}



/* Check if we can expire a direct mount (possibly a tree) */

static struct dentry *autofs4_expire_direct(struct super_block *sb,

struct dentry *autofs4_expire_direct(struct super_block *sb,

				     struct vfsmount *mnt,

				     struct autofs_sb_info *sbi,

				     int how)
@@ -283,7 +283,7 @@ static struct dentry *autofs4_expire_direct(struct super_block *sb, 
 *  - it is unused by any user process

 *  - it has been unused for exp_timeout time

 */

static struct dentry *autofs4_expire_indirect(struct super_block *sb,

struct dentry *autofs4_expire_indirect(struct super_block *sb,

				       struct vfsmount *mnt,

				       struct autofs_sb_info *sbi,

				       int how)

fs/autofs4/init.c

+10 −1
Original line number Diff line number Diff line
@@ -29,11 +29,20 @@ static struct file_system_type autofs_fs_type = { 


static int __init init_autofs4_fs(void)

{

	return register_filesystem(&autofs_fs_type);

	int err;



	err = register_filesystem(&autofs_fs_type);

	if (err)

		return err;



	autofs_dev_ioctl_init();



	return err;

}



static void __exit exit_autofs4_fs(void)

{

	autofs_dev_ioctl_exit();

	unregister_filesystem(&autofs_fs_type);

}