Kill CL_PROPAGATION, sanitize fs/pnode.c:get_source()

First of all, get_source() never results in CL_PROPAGATION
alone.  We either get CL_MAKE_SHARED (for the continuation
of peer group) or CL_SLAVE (slave that is not shared) or both
(beginning of peer group among slaves).  Massage the code to
make that explicit, kill CL_PROPAGATION test in clone_mnt()
(nothing sets CL_MAKE_SHARED without CL_PROPAGATION and in
clone_mnt() we are checking CL_PROPAGATION after we'd found
that there's no CL_SLAVE, so the check for CL_MAKE_SHARED
would do just as well).

Fix comments, while we are at it...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/namespace.c b/fs/namespace.c
index c768f733c8d6585a87551190bdf1b71a14cab9fe..25c1dcf9e9eb4451b2447fc7e0a89be33447ad27 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -573,7 +573,7 @@ static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
                        mnt->mnt_master = old;
                        CLEAR_MNT_SHARED(mnt);
                } else if (!(flag & CL_PRIVATE)) {
-                       if ((flag & CL_PROPAGATION) || IS_MNT_SHARED(old))
+                       if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
                                list_add(&mnt->mnt_share, &old->mnt_share);
                        if (IS_MNT_SLAVE(old))
                                list_add(&mnt->mnt_slave, &old->mnt_slave);

diff --git a/fs/pnode.c b/fs/pnode.c
index 8d5f392ec3d39fa12a025ec3a6045b7ef8f790a4..5cc564a83149a5fc311b57d87793febbdcfd4f27 100644 (file)
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -86,7 +86,7 @@ static int do_make_slave(struct vfsmount *mnt)
 
        /*
         * slave 'mnt' to a peer mount that has the
-        * same root dentry. If none is available than
+        * same root dentry. If none is available then
         * slave it to anything that is available.
         */
        while ((peer_mnt = next_peer(peer_mnt)) != mnt &&
@@ -147,6 +147,11 @@ void change_mnt_propagation(struct vfsmount *mnt, int type)
  * get the next mount in the propagation tree.
  * @m: the mount seen last
  * @origin: the original mount from where the tree walk initiated
+ *
+ * Note that peer groups form contiguous segments of slave lists.
+ * We rely on that in get_source() to be able to find out if
+ * vfsmount found while iterating with propagation_next() is
+ * a peer of one we'd found earlier.
  */
 static struct vfsmount *propagation_next(struct vfsmount *m,
                                         struct vfsmount *origin)
@@ -186,10 +191,6 @@ static struct vfsmount *get_source(struct vfsmount *dest,
 {
        struct vfsmount *p_last_src = NULL;
        struct vfsmount *p_last_dest = NULL;
-       *type = CL_PROPAGATION;
-
-       if (IS_MNT_SHARED(dest))
-               *type |= CL_MAKE_SHARED;
 
        while (last_dest != dest->mnt_master) {
                p_last_dest = last_dest;
@@ -202,13 +203,18 @@ static struct vfsmount *get_source(struct vfsmount *dest,
                do {
                        p_last_dest = next_peer(p_last_dest);
                } while (IS_MNT_NEW(p_last_dest));
+               /* is that a peer of the earlier? */
+               if (dest == p_last_dest) {
+                       *type = CL_MAKE_SHARED;
+                       return p_last_src;
+               }
        }
-
-       if (dest != p_last_dest) {
-               *type |= CL_SLAVE;
-               return last_src;
-       } else
-               return p_last_src;
+       /* slave of the earlier, then */
+       *type = CL_SLAVE;
+       /* beginning of peer group among the slaves? */
+       if (IS_MNT_SHARED(dest))
+               *type |= CL_MAKE_SHARED;
+       return last_src;
 }
 
 /*

diff --git a/fs/pnode.h b/fs/pnode.h
index 958665d662af24f4e7bea120a959c6220a91b1f5..6c7ef3252a26dc2bf99d3bca3efde6c9eff2efd3 100644 (file)
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -21,8 +21,7 @@
 #define CL_SLAVE               0x02
 #define CL_COPY_ALL            0x04
 #define CL_MAKE_SHARED                 0x08
-#define CL_PROPAGATION                 0x10
-#define CL_PRIVATE             0x20
+#define CL_PRIVATE             0x10
 
 static inline void set_mnt_shared(struct vfsmount *mnt)
 {