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Subject[PATCH 2/2] shared mounts: save mount flag space
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Date
Remaining mount flags are becoming scarce (just 11 bits)
and shared mount code uses 4 though one would suffice.

I think this should go into 2.6.15, fixing it later would be breaking
userspace ABI.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
---
Index: linux/fs/pnode.c
===================================================================
--- linux.orig/fs/pnode.c 2005-11-24 16:21:02.000000000 +0100
+++ linux/fs/pnode.c 2005-11-24 16:33:12.000000000 +0100
@@ -72,17 +72,17 @@ static int do_make_slave(struct vfsmount
return 0;
}

-void change_mnt_propagation(struct vfsmount *mnt, int type)
+void change_mnt_propagation(struct vfsmount *mnt, enum propagation_type type)
{
- if (type == MS_SHARED) {
+ if (type == PT_SHARED) {
set_mnt_shared(mnt);
return;
}
do_make_slave(mnt);
- if (type != MS_SLAVE) {
+ if (type != PT_SLAVE) {
list_del_init(&mnt->mnt_slave);
mnt->mnt_master = NULL;
- if (type == MS_UNBINDABLE)
+ if (type == PT_UNBINDABLE)
mnt->mnt_flags |= MNT_UNBINDABLE;
}
}
Index: linux/include/linux/fs.h
===================================================================
--- linux.orig/include/linux/fs.h 2005-11-24 16:21:06.000000000 +0100
+++ linux/include/linux/fs.h 2005-11-24 16:36:44.000000000 +0100
@@ -104,10 +104,7 @@ extern int dir_notify_enable;
#define MS_REC 16384
#define MS_VERBOSE 32768
#define MS_POSIXACL (1<<16) /* VFS does not apply the umask */
-#define MS_UNBINDABLE (1<<17) /* change to unbindable */
-#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_PROPAGATION (1<<17) /* change propagation property */
#define MS_ACTIVE (1<<30)
#define MS_NOUSER (1<<31)

Index: linux/fs/pnode.h
===================================================================
--- linux.orig/fs/pnode.h 2005-11-24 16:32:19.000000000 +0100
+++ linux/fs/pnode.h 2005-11-24 16:32:45.000000000 +0100
@@ -23,13 +23,20 @@
#define CL_MAKE_SHARED 0x08
#define CL_PROPAGATION 0x10

+enum propagation_type {
+ PT_UNBINDABLE,
+ PT_PRIVATE,
+ PT_SLAVE,
+ PT_SHARED,
+};
+
static inline void set_mnt_shared(struct vfsmount *mnt)
{
mnt->mnt_flags &= ~MNT_PNODE_MASK;
mnt->mnt_flags |= MNT_SHARED;
}

-void change_mnt_propagation(struct vfsmount *, int);
+void change_mnt_propagation(struct vfsmount *, enum propagation_type);
int propagate_mnt(struct vfsmount *, struct dentry *, struct vfsmount *,
struct list_head *);
int propagate_umount(struct list_head *);
Index: linux/fs/namespace.c
===================================================================
--- linux.orig/fs/namespace.c 2005-11-24 16:21:02.000000000 +0100
+++ linux/fs/namespace.c 2005-11-24 16:37:34.000000000 +0100
@@ -490,7 +490,7 @@ void umount_tree(struct vfsmount *mnt, i
list_del_init(&p->mnt_child);
if (p->mnt_parent != p)
mnt->mnt_mountpoint->d_mounted--;
- change_mnt_propagation(p, MS_PRIVATE);
+ change_mnt_propagation(p, PT_PRIVATE);
}
}

@@ -835,15 +835,25 @@ out_unlock:
/*
* recursively change the type of the mountpoint.
*/
-static int do_change_type(struct nameidata *nd, int flag)
+static int do_change_type(struct nameidata *nd, int recurse, char *name)
{
struct vfsmount *m, *mnt = nd->mnt;
- int recurse = flag & MS_REC;
- int type = flag & ~MS_REC;
+ enum propagation_type type;

if (nd->dentry != nd->mnt->mnt_root)
return -EINVAL;

+ if (strcmp(name, "unbindable") == 0)
+ type = PT_UNBINDABLE;
+ else if (strcmp(name, "private") == 0)
+ type = PT_PRIVATE;
+ else if (strcmp(name, "slave") == 0)
+ type = PT_SLAVE;
+ else if (strcmp(name, "shared") == 0)
+ type = PT_SHARED;
+ else
+ return -EINVAL;
+
down_write(&namespace_sem);
spin_lock(&vfsmount_lock);
for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
@@ -1302,8 +1312,8 @@ long do_mount(char *dev_name, char *dir_
data_page);
else if (flags & MS_BIND)
retval = do_loopback(&nd, dev_name, flags & MS_REC);
- else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
- retval = do_change_type(&nd, flags);
+ else if (flags & MS_PROPAGATION)
+ retval = do_change_type(&nd, flags & MS_REC, data_page);
else if (flags & MS_MOVE)
retval = do_move_mount(&nd, dev_name);
else
-
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