With MS_REMOUNT, it is difficult to change mount flags individually,
without touching other mount flags or options, having to parse
/proc/mounts to get the old flag values and options.
It is also difficult to change a mount flag recursively, having to
walk the mount tree in userspace.
This patch solves this problem by generalizing do_change_type() so
that not only the propagation property can be changed, but mnt_flags
can be set/cleared individually.
From: Miklos Szeredi <mszeredi@xxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
---
Index: linux/fs/namespace.c
===================================================================
--- linux.orig/fs/namespace.c 2007-04-13 13:04:04.000000000 +0200
+++ linux/fs/namespace.c 2007-04-13 13:04:29.000000000 +0200
@@ -955,19 +956,28 @@ out_unlock:
/*
* recursively change the type of the mountpoint.
*/
-static int do_change_type(struct nameidata *nd, int flag)
+static int do_change_mnt(struct nameidata *nd, int flag, int mnt_flags)
{
struct vfsmount *m, *mnt = nd->mnt;
int recurse = flag & MS_REC;
- int type = flag & ~MS_REC;
+ int type = flag & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE);
if (nd->dentry != nd->mnt->mnt_root)
return -EINVAL;
down_write(&namespace_sem);
spin_lock(&vfsmount_lock);
- for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
- change_mnt_propagation(m, type);
+ for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) {
+ if (type)
+ change_mnt_propagation(m, type);
+
+ if (flag & (MS_SETFLAGS | MS_CLEARFLAGS))
+ m->mnt_flags = mnt_flags;
+ else if (flag & MS_SETFLAGS)
+ m->mnt_flags |= mnt_flags;
+ else if (flag & MS_CLEARFLAGS)
+ m->mnt_flags &= ~mnt_flags;
+ }
spin_unlock(&vfsmount_lock);
up_write(&namespace_sem);
return 0;
@@ -1514,8 +1526,9 @@ long do_mount(char *dev_name, char *dir_
data_page);
else if (flags & MS_BIND)
retval = do_loopback(&nd, dev_name, flags);
- else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
- retval = do_change_type(&nd, flags);
+ else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE |
+ MS_SETFLAGS | MS_CLEARFLAGS))
+ retval = do_change_mnt(&nd, flags, mnt_flags);
else if (flags & MS_MOVE)
retval = do_move_mount(&nd, dev_name);
else
Index: linux/include/linux/fs.h
===================================================================
--- linux.orig/include/linux/fs.h 2007-04-13 13:04:04.000000000 +0200
+++ linux/include/linux/fs.h 2007-04-13 13:04:29.000000000 +0200
@@ -127,6 +127,9 @@ extern int dir_notify_enable;
#define MS_SHARED (1<<20) /* change to shared */
#define MS_RELATIME (1<<21) /* Update atime relative to mtime/ctime. */
#define MS_SETUSER (1<<22) /* set mnt_uid to current user */
+#define MS_SETFLAGS (1<<23) /* set specified mount flags */
+#define MS_CLEARFLAGS (1<<24) /* clear specified mount flags */
+/* MS_SETFLAGS | MS_CLEARFLAGS: change mount flags to specified */
#define MS_ACTIVE (1<<30)
#define MS_NOUSER (1<<31)
--
-
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
