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Date
From
, miklos@szeredi.hu, Janak Desai <janak@us.ibm.com>, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 4/7] shared subtree
Content-Type: text/x-patch; name=move.patch
Content-Disposition: inline; filename=move.patch

Adds ability to move a shared/private/slave/unclone tree to any other
shared/private/slave/unclone tree. Also incorporates the same behavior
for pivot_root()

RP


Signed by Ram Pai (linuxram@us.ibm.com)

fs/namespace.c | 196 +++++++++++++++++++++++++++++++++++++++++++-------
include/linux/mount.h | 2
2 files changed, 173 insertions(+), 25 deletions(-)
Index: 2.6.12.work2/fs/namespace.c
===================================================================
--- 2.6.12.work2.orig/fs/namespace.c
+++ 2.6.12.work2/fs/namespace.c
@@ -772,9 +772,12 @@ static void abort_attach_recursive_mnt(s
list_del_init(head);
}

+
/*
* @source_mnt : mount tree to be attached
* @nd : place the mount tree @source_mnt is attached
+ * @move : use the move semantics if set, else use normal attach semantics
+ * as explained below
*
* NOTE: in the table below explains the semantics when a source vfsmount
* of a given type is attached to a destination vfsmount of a give type.
@@ -801,12 +804,41 @@ static void abort_attach_recursive_mnt(s
* | | | | | |
* ********************************************************************
*
- * (++) the mount will be propogated to all the vfsmounts in the pnode tree
+ * (++) the mount is propogated to all the vfsmounts in the pnode tree
* of the destination vfsmount, and all the non-slave new mounts in
* destination vfsmount will be added the source vfsmount's pnode.
- * (+) the mount will be propogated to the destination vfsmount
+ * (+) the mount is propogated to the destination vfsmount
* and the new mount will be added to the source vfsmount's pnode.
*
+ * ---------------------------------------------------------------------
+ * | MOVE MOUNT OPERATION |
+ * |*******************************************************************|
+ * | dest --> | shared | private | slave |unclonable |
+ * | source | | | | |
+ * | | | | | | |
+ * | v | | | | |
+ * |*******************************************************************|
+ * | | | | | |
+ * | shared | shared (++) | shared (+)|shared (+)| shared (+)|
+ * | | | | | |
+ * | | | | | |
+ * | private | shared (+) | private | private | private |
+ * | | | | | |
+ * | | | | | |
+ * | slave | shared (+++) | slave | slave | slave |
+ * | | | | | |
+ * | | | | | |
+ * | unclonable| invalid | unclonable |unclonable| unclonable|
+ * | | | | | |
+ * | | | | | |
+ * ********************************************************************
+ *
+ * (+++) the mount is propogated to all the vfsmounts in the pnode tree
+ * of the destination vfsmount, and all the new mounts is
+ * added to a new pnode , which is a slave pnode of the
+ * source vfsmount's pnode.
+ *
+ *
* if the source mount is a tree, the operations explained above is
* applied to each vfsmount in the tree.
*
@@ -815,7 +847,7 @@ static void abort_attach_recursive_mnt(s
*
*/
static int attach_recursive_mnt(struct vfsmount *source_mnt,
- struct nameidata *nd)
+ struct nameidata *nd, int move)
{
struct vfsmount *mntpt_mnt, *last, *m, *p;
struct vfspnode *src_pnode, *dest_pnode, *tmp_pnode;
@@ -849,8 +881,8 @@ static int attach_recursive_mnt(struct v
list_add_tail(&mnt_list_head, &source_mnt->mnt_list);

for (m = source_mnt; m; m = next_mnt(m, source_mnt)) {
-
- BUG_ON(IS_MNT_UNCLONE(m));
+ int unclone = IS_MNT_UNCLONE(m);
+ int slave = IS_MNT_SLAVE(m);

while (p && p != m->mnt_parent)
p = p->mnt_parent;
@@ -866,7 +898,7 @@ static int attach_recursive_mnt(struct v

dest_pnode = IS_MNT_SHARED(mntpt_mnt) ?
mntpt_mnt->mnt_pnode : NULL;
- src_pnode = (IS_MNT_SHARED(m))?
+ src_pnode = (IS_MNT_SHARED(m) || (move && slave))?
m->mnt_pnode : NULL;

/*
@@ -882,7 +914,7 @@ static int attach_recursive_mnt(struct v
list_del_init(&m->mnt_list);
list_add_tail(&tmp_pnode->pnode_peer_slave, &pnodehead);

- if (dest_pnode) {
+ if (dest_pnode && !unclone) {
if ((ret = pnode_prepare_mount(dest_pnode, tmp_pnode,
mntpt_dentry, m, mntpt_mnt))) {
tmp_pnode->pnode_master = src_pnode;
@@ -890,23 +922,33 @@ static int attach_recursive_mnt(struct v
last = m;
goto error;
}
+ if (move && dest_pnode && slave)
+ SET_PNODE_SLAVE(tmp_pnode);
} else {
if (m == m->mnt_parent)
do_attach_prepare_mnt(mntpt_mnt,
mntpt_dentry, m, 0);
- pnode_add_member_mnt(tmp_pnode, m);
- if (!src_pnode) {
- set_mnt_private(m);
+ if (move && slave)
+ pnode_add_slave_mnt(tmp_pnode, m);
+ else {
+ pnode_add_member_mnt(tmp_pnode, m);
+ if (unclone) {
+ BUG_ON(!move);
+ set_mnt_unclone(m);
+ m->mnt_pnode = tmp_pnode;
+ SET_PNODE_DELETE(tmp_pnode);
+ } else if (!src_pnode) {
+ set_mnt_private(m);
+ m->mnt_pnode = tmp_pnode;
+ SET_PNODE_DELETE(tmp_pnode);
+ }
/*
- * NOTE: set_mnt_private()
- * resets m->mnt_pnode.
- * Reinitialize it. This is needed to
- * decrement the refcount on the
- * pnode when the mount 'm' is
- * unlinked in pnode_commit_mount().
+ * NOTE: set_mnt_private() & set_mnt_unclone()
+ * resets m->mnt_pnode. Hence reinitialize it.
+ * We need this to decrement the refcount
+ * on the pnode when the mount 'm' is
+ * unlinked in pnode_commit_mount()
*/
- m->mnt_pnode = tmp_pnode;
- SET_PNODE_DELETE(tmp_pnode);
}
}

@@ -931,6 +973,46 @@ error:
return 1;
}

+static void
+detach_recursive_mnt(struct vfsmount *source_mnt, struct nameidata *nd)
+{
+ struct vfsmount *m;
+
+ detach_mnt(source_mnt, nd);
+ spin_lock(&vfspnode_lock);
+ for (m = source_mnt; m; m = next_mnt(m, source_mnt)) {
+ list_del_init(&m->mnt_pnode_mntlist);
+ list_del_init(&m->mnt_list);
+ if (m != source_mnt)
+ list_add_tail(&m->mnt_list, &source_mnt->mnt_list);
+ }
+ spin_unlock(&vfspnode_lock);
+}
+
+static void
+undo_detach_recursive_mnt(struct vfsmount *mnt, struct nameidata *nd)
+{
+ struct vfsmount *m;
+ LIST_HEAD(head);
+
+ spin_lock(&vfspnode_lock);
+ for (m = mnt; m; m = next_mnt(m, mnt)) {
+ if (m->mnt_pnode) {
+ if (IS_MNT_SHARED(m))
+ list_add(&m->mnt_pnode_mntlist,
+ &m->mnt_pnode->pnode_vfs);
+ if (IS_MNT_SLAVE(m))
+ list_add(&m->mnt_pnode_mntlist,
+ &m->mnt_pnode->pnode_slavevfs);
+ }
+ }
+ attach_mnt(mnt, nd);
+ spin_unlock(&vfspnode_lock);
+
+ list_add_tail(&head, &mnt->mnt_list);
+ list_splice(&head, nd->mnt->mnt_namespace->list.prev);
+}
+
static int graft_tree(struct vfsmount *mnt, struct nameidata *nd)
{
int err, ret;
@@ -957,7 +1039,7 @@ static int graft_tree(struct vfsmount *m
ret = (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry));
spin_unlock(&vfsmount_lock);
if (ret)
- err = attach_recursive_mnt(mnt, nd);
+ err = attach_recursive_mnt(mnt, nd, 0);
out_unlock:
up(&nd->dentry->d_inode->i_sem);
if (!err)
@@ -1311,6 +1393,19 @@ static int do_remount(struct nameidata *
return err;
}

+/*
+ * return 1 if the mount tree contains a unclonable mount
+ */
+static inline int tree_contains_unclone(struct vfsmount *mnt)
+{
+ struct vfsmount *p;
+ for (p = mnt; p; p = next_mnt(p, mnt)) {
+ if (IS_MNT_UNCLONE(p))
+ return 1;
+ }
+ return 0;
+}
+
static int do_move_mount(struct nameidata *nd, char *old_name)
{
struct nameidata old_nd, parent_nd;
@@ -1351,14 +1446,35 @@ static int do_move_mount(struct nameidat
S_ISDIR(old_nd.dentry->d_inode->i_mode))
goto out2;

+ /*
+ * Don't move a mount in a shared parent.
+ */
+ if (old_nd.mnt->mnt_parent &&
+ IS_MNT_SHARED(old_nd.mnt->mnt_parent))
+ goto out2;
+
+ /*
+ * Don't move a mount tree having unclonable
+ * mounts, under a shared mount
+ */
+ if (IS_MNT_SHARED(nd->mnt) &&
+ tree_contains_unclone(old_nd.mnt))
+ goto out2;
+
err = -ELOOP;
for (p = nd->mnt; p->mnt_parent!=p; p = p->mnt_parent)
if (p == old_nd.mnt)
goto out2;
err = 0;

- detach_mnt(old_nd.mnt, &parent_nd);
- attach_mnt(old_nd.mnt, nd);
+ detach_recursive_mnt(old_nd.mnt, &parent_nd);
+ spin_unlock(&vfsmount_lock);
+ if ((err = attach_recursive_mnt(old_nd.mnt, nd, 1))) {
+ undo_detach_recursive_mnt(old_nd.mnt, &parent_nd);
+ goto out1;
+ }
+ spin_lock(&vfsmount_lock);
+ mntput(old_nd.mnt);

/* if the mount is moved, it should no longer be expire
* automatically */
@@ -1949,6 +2065,16 @@ asmlinkage long sys_pivot_root(const cha
goto out2; /* not a mountpoint */
if (new_nd.mnt->mnt_root != new_nd.dentry)
goto out2; /* not a mountpoint */
+ /*
+ * Don't move a mount in a shared parent.
+ */
+ if(user_nd.mnt->mnt_parent &&
+ IS_MNT_SHARED(user_nd.mnt->mnt_parent))
+ goto out2;
+ if(new_nd.mnt->mnt_parent &&
+ IS_MNT_SHARED(new_nd.mnt->mnt_parent))
+ goto out2;
+
tmp = old_nd.mnt; /* make sure we can reach put_old from new_root */
spin_lock(&vfsmount_lock);
if (tmp != new_nd.mnt) {
@@ -1963,10 +2089,30 @@ asmlinkage long sys_pivot_root(const cha
goto out3;
} else if (!is_subdir(old_nd.dentry, new_nd.dentry))
goto out3;
- detach_mnt(new_nd.mnt, &parent_nd);
- detach_mnt(user_nd.mnt, &root_parent);
- attach_mnt(user_nd.mnt, &old_nd); /* mount old root on put_old */
- attach_mnt(new_nd.mnt, &root_parent); /* mount new_root on / */
+
+ detach_recursive_mnt(user_nd.mnt, &root_parent);
+ detach_recursive_mnt(new_nd.mnt, &parent_nd);
+
+ spin_unlock(&vfsmount_lock);
+ if ((error = attach_recursive_mnt(user_nd.mnt, &old_nd, 1))) {
+ spin_lock(&vfsmount_lock);
+ undo_detach_recursive_mnt(new_nd.mnt, &parent_nd);
+ undo_detach_recursive_mnt(user_nd.mnt, &root_parent);
+ goto out3;
+ }
+ spin_lock(&vfsmount_lock);
+ mntput(user_nd.mnt);
+
+ spin_unlock(&vfsmount_lock);
+ if ((error = attach_recursive_mnt(new_nd.mnt, &root_parent, 1))) {
+ spin_lock(&vfsmount_lock);
+ undo_detach_recursive_mnt(new_nd.mnt, &parent_nd);
+ undo_detach_recursive_mnt(user_nd.mnt, &root_parent);
+ goto out3;
+ }
+ spin_lock(&vfsmount_lock);
+ mntput(new_nd.mnt);
+
spin_unlock(&vfsmount_lock);
chroot_fs_refs(&user_nd, &new_nd);
security_sb_post_pivotroot(&user_nd, &new_nd);
Index: 2.6.12.work2/include/linux/mount.h
===================================================================
--- 2.6.12.work2.orig/include/linux/mount.h
+++ 2.6.12.work2/include/linux/mount.h
@@ -29,6 +29,8 @@
#define IS_MNT_SLAVE(mnt) (mnt->mnt_flags & MNT_SLAVE)
#define IS_MNT_PRIVATE(mnt) (mnt->mnt_flags & MNT_PRIVATE)
#define IS_MNT_UNCLONE(mnt) (mnt->mnt_flags & MNT_UNCLONE)
+#define GET_MNT_TYPE(mnt) (mnt->mnt_flags & MNT_PNODE_MASK)
+#define SET_MNT_TYPE(mnt, type) (mnt->mnt_flags |= (type & MNT_PNODE_MASK))

#define CLEAR_MNT_SHARED(mnt) (mnt->mnt_flags &= ~(MNT_PNODE_MASK & MNT_SHARED))
#define CLEAR_MNT_PRIVATE(mnt) (mnt->mnt_flags &= ~(MNT_PNODE_MASK & MNT_PRIVATE))
-
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