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

[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
......@@ -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);
......
......@@ -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;
}
}
......
......@@ -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
......
......@@ -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)
......
......@@ -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;
};
......
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