[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: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/namespace.c b/fs/namespace.c
index 4b1af01..46f99bc 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -67,6 +67,8 @@
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 @@
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);
diff --git a/fs/pnode.c b/fs/pnode.c
index 7bc942d..f73eba2 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -17,13 +17,61 @@
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;
}
}
diff --git a/fs/pnode.h b/fs/pnode.h
index 9b88ba0..b59f0e9 100644
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -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
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 8bdb504..eef66f5 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -105,6 +105,7 @@
#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)
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 2582559..7e133ae 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -38,6 +38,9 @@
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;
};