Al, you might have already fixed this as part of your mount flag
rewrite, but here's a patch to clean up some problems with shared
mount flag propagation that I ran into while working on union mounts.
Against 2.6.32.
-VAL
commit 3f436c4466f278900d451494b317f6bb80b4c24b
Author: Valerie Aurora <vaurora@xxxxxxxxxx>
Date: Tue Jan 26 11:09:00 2010 -0800
VFS: Clean up shared mount flag propagation
The handling of mount flags in set_mnt_shared() got a little tangled
up during previous cleanups, with the following problems:
* MNT_PNODE_MASK is defined as a literal constant when it should be a
bitwise xor of other MNT_* flags
* set_mnt_shared() clears and then sets MNT_SHARED (part of MNT_PNODE_MASK)
* MNT_PNODE_MASK could use a comment in mount.h
* MNT_PNODE_MASK is a terrible name, change to MNT_SHARED_MASK
This patch fixes these problems.
diff --git a/fs/pnode.h b/fs/pnode.h
index 958665d..adc52ca 100644
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -26,7 +26,7 @@
static inline void set_mnt_shared(struct vfsmount *mnt)
{
- mnt->mnt_flags &= ~MNT_PNODE_MASK;
+ mnt->mnt_flags &= ~MNT_SHARED_MASK;
mnt->mnt_flags |= MNT_SHARED;
}
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 5d52753..257985f 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -34,7 +34,15 @@ struct mnt_namespace;
#define MNT_SHARED 0x1000 /* if the vfsmount is a shared mount */
#define MNT_UNBINDABLE 0x2000 /* if the vfsmount is a unbindable mount */
-#define MNT_PNODE_MASK 0x3000 /* propagation flag mask */
+/*
+ * MNT_SHARED_MASK is the set of flags that should be cleared when a
+ * mount becomes shared. Currently, this is only the flag that says a
+ * mount cannot be bind mounted, since this is how we create a mount
+ * that shares events with another mount. If you add a new MNT_*
+ * flag, consider how it interacts with shared mounts.
+ */
+#define MNT_SHARED_MASK (MNT_UNBINDABLE)
+
struct vfsmount {
struct list_head mnt_hash;
--
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