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Commit a58b0eb8 authored by Ram Pai's avatar Ram Pai Committed by Linus Torvalds
Browse files

[PATCH] introduce slave mounts 



A slave mount always has a master mount from which it receives
mount/umount events.  Unlike shared mount the event propagation does not
flow from the slave mount to the master.

Signed-off-by: default avatarRam Pai <linuxram@us.ibm.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent a05964f3

fs/namespace.c

+3 −1
Original line number Diff line number Diff line
@@ -67,6 +67,8 @@ struct vfsmount *alloc_vfsmnt(const char *name) 
		INIT_LIST_HEAD(&mnt->mnt_list);

		INIT_LIST_HEAD(&mnt->mnt_expire);

		INIT_LIST_HEAD(&mnt->mnt_share);

		INIT_LIST_HEAD(&mnt->mnt_slave_list);

		INIT_LIST_HEAD(&mnt->mnt_slave);

		if (name) {

			int size = strlen(name) + 1;

			char *newname = kmalloc(size, GFP_KERNEL);
@@ -1243,7 +1245,7 @@ long do_mount(char *dev_name, char *dir_name, char *type_page, 
				    data_page);

	else if (flags & MS_BIND)

		retval = do_loopback(&nd, dev_name, flags & MS_REC);

	else if (flags & (MS_SHARED | MS_PRIVATE))

	else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE))

		retval = do_change_type(&nd, flags);

	else if (flags & MS_MOVE)

		retval = do_move_mount(&nd, dev_name);

fs/pnode.c

+51 −3
Original line number Diff line number Diff line
@@ -17,13 +17,61 @@ static inline struct vfsmount *next_peer(struct vfsmount *p) 
	return list_entry(p->mnt_share.next, struct vfsmount, mnt_share);

}



static int do_make_slave(struct vfsmount *mnt)

{

	struct vfsmount *peer_mnt = mnt, *master = mnt->mnt_master;

	struct vfsmount *slave_mnt;



	/*

	 * slave 'mnt' to a peer mount that has the

	 * same root dentry. If none is available than

	 * slave it to anything that is available.

	 */

	while ((peer_mnt = next_peer(peer_mnt)) != mnt &&

	       peer_mnt->mnt_root != mnt->mnt_root) ;



	if (peer_mnt == mnt) {

		peer_mnt = next_peer(mnt);

		if (peer_mnt == mnt)

			peer_mnt = NULL;

	}

	list_del_init(&mnt->mnt_share);



	if (peer_mnt)

		master = peer_mnt;



	if (master) {

		list_for_each_entry(slave_mnt, &mnt->mnt_slave_list, mnt_slave)

			slave_mnt->mnt_master = master;

		list_del(&mnt->mnt_slave);

		list_add(&mnt->mnt_slave, &master->mnt_slave_list);

		list_splice(&mnt->mnt_slave_list, master->mnt_slave_list.prev);

		INIT_LIST_HEAD(&mnt->mnt_slave_list);

	} else {

		struct list_head *p = &mnt->mnt_slave_list;

		while (!list_empty(p)) {

                        slave_mnt = list_entry(p->next,

					struct vfsmount, mnt_slave);

			list_del_init(&slave_mnt->mnt_slave);

			slave_mnt->mnt_master = NULL;

		}

	}

	mnt->mnt_master = master;

	CLEAR_MNT_SHARED(mnt);

	INIT_LIST_HEAD(&mnt->mnt_slave_list);

	return 0;

}



void change_mnt_propagation(struct vfsmount *mnt, int type)

{

	if (type == MS_SHARED) {

		set_mnt_shared(mnt);

	} else {

		list_del_init(&mnt->mnt_share);

		mnt->mnt_flags &= ~MNT_PNODE_MASK;

		return;

	}

	do_make_slave(mnt);

	if (type != MS_SLAVE) {

		list_del_init(&mnt->mnt_slave);

		mnt->mnt_master = NULL;

	}

}

fs/pnode.h

+2 −0
Original line number Diff line number Diff line
@@ -12,10 +12,12 @@ 
#include <linux/mount.h>



#define IS_MNT_SHARED(mnt) (mnt->mnt_flags & MNT_SHARED)

#define IS_MNT_SLAVE(mnt) (mnt->mnt_master)

#define IS_MNT_NEW(mnt)  (!mnt->mnt_namespace)

#define CLEAR_MNT_SHARED(mnt) (mnt->mnt_flags &= ~MNT_SHARED)



#define CL_EXPIRE    		0x01

#define CL_SLAVE     		0x02

#define CL_COPY_ALL 		0x04

#define CL_MAKE_SHARED 		0x08

#define CL_PROPAGATION 		0x10

include/linux/fs.h

+1 −0
Original line number Diff line number Diff line
@@ -105,6 +105,7 @@ extern int dir_notify_enable; 
#define MS_REC		16384

#define MS_VERBOSE	32768

#define MS_PRIVATE	(1<<18)	/* change to private */

#define MS_SLAVE	(1<<19)	/* change to slave */

#define MS_SHARED	(1<<20)	/* change to shared */

#define MS_POSIXACL	(1<<16)	/* VFS does not apply the umask */

#define MS_ACTIVE	(1<<30)

include/linux/mount.h

+3 −0
Original line number Diff line number Diff line
@@ -38,6 +38,9 @@ struct vfsmount { 
	struct list_head mnt_list;

	struct list_head mnt_expire;	/* link in fs-specific expiry list */

	struct list_head mnt_share;	/* circular list of shared mounts */

	struct list_head mnt_slave_list;/* list of slave mounts */

	struct list_head mnt_slave;	/* slave list entry */

	struct vfsmount *mnt_master;	/* slave is on master->mnt_slave_list */

	struct namespace *mnt_namespace; /* containing namespace */

	int mnt_pinned;

};