(no subject)

Ram Pai
2005-07-25T23:00:07Z

, miklos@szeredi.hu, Janak Desai <janak@us.ibm.com>, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 3/7] shared subtree
Content-Type: text/x-patch; name=rbind.patch
Content-Disposition: inline; filename=rbind.patch

Adds the ability to bind/rbind a shared/private/slave subtree and set up
propogation wherever needed.

RP

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

fs/namespace.c | 660 ++++++++++++++++++++++++++++++++++++++++------
fs/pnode.c | 235 ++++++++++++++++
include/linux/dcache.h | 2
include/linux/fs.h | 5
include/linux/namespace.h | 1
5 files changed, 826 insertions(+), 77 deletions(-)

Index: 2.6.12.work2/fs/namespace.c
===================================================================
--- 2.6.12.work2.orig/fs/namespace.c
+++ 2.6.12.work2/fs/namespace.c
@@ -42,7 +42,8 @@ static inline int sysfs_init(void)

static struct list_head *mount_hashtable;
static int hash_mask, hash_bits;
-static kmem_cache_t *mnt_cache;
+static kmem_cache_t *mnt_cache;
+static struct rw_semaphore namespace_sem;

static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
{
@@ -54,7 +55,7 @@ static inline unsigned long hash(struct

struct vfsmount *alloc_vfsmnt(const char *name)
{
- struct vfsmount *mnt = kmem_cache_alloc(mnt_cache, GFP_KERNEL);
+ struct vfsmount *mnt = kmem_cache_alloc(mnt_cache, GFP_KERNEL);
if (mnt) {
memset(mnt, 0, sizeof(struct vfsmount));
atomic_set(&mnt->mnt_count,1);
@@ -86,7 +87,8 @@ void free_vfsmnt(struct vfsmount *mnt)
* Now, lookup_mnt increments the ref count before returning
* the vfsmount struct.
*/
-struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
+struct vfsmount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry,
+ struct dentry *root)
{
struct list_head * head = mount_hashtable + hash(mnt, dentry);
struct list_head * tmp = head;
@@ -99,7 +101,8 @@ struct vfsmount *lookup_mnt(struct vfsmo
if (tmp == head)
break;
p = list_entry(tmp, struct vfsmount, mnt_hash);
- if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) {
+ if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry &&
+ (root == NULL || p->mnt_root == root)) {
found = mntget(p);
break;
}
@@ -108,6 +111,37 @@ struct vfsmount *lookup_mnt(struct vfsmo
return found;
}

+struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
+{
+ return __lookup_mnt(mnt, dentry, NULL);
+}
+
+static struct vfsmount *
+clone_mnt(struct vfsmount *old, struct dentry *root)
+{
+ struct super_block *sb = old->mnt_sb;
+ struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname);
+
+ if (mnt) {
+ mnt->mnt_flags = old->mnt_flags;
+ atomic_inc(&sb->s_active);
+ mnt->mnt_sb = sb;
+ mnt->mnt_root = dget(root);
+ mnt->mnt_mountpoint = mnt->mnt_root;
+ mnt->mnt_parent = mnt;
+ mnt->mnt_namespace = old->mnt_namespace;
+ mnt->mnt_pnode = get_pnode(old->mnt_pnode);
+
+ /* stick the duplicate mount on the same expiry list
+ * as the original if that was on one */
+ spin_lock(&vfsmount_lock);
+ if (!list_empty(&old->mnt_fslink))
+ list_add(&mnt->mnt_fslink, &old->mnt_fslink);
+ spin_unlock(&vfsmount_lock);
+ }
+ return mnt;
+}
+
static inline int check_mnt(struct vfsmount *mnt)
{
return mnt->mnt_namespace == current->namespace;
@@ -128,11 +162,71 @@ static void attach_mnt(struct vfsmount *
{
mnt->mnt_parent = mntget(nd->mnt);
mnt->mnt_mountpoint = dget(nd->dentry);
- list_add(&mnt->mnt_hash, mount_hashtable+hash(nd->mnt, nd->dentry));
+ mnt->mnt_namespace = nd->mnt->mnt_namespace;
+ list_add_tail(&mnt->mnt_hash,
+ mount_hashtable+hash(nd->mnt, nd->dentry));
list_add_tail(&mnt->mnt_child, &nd->mnt->mnt_mounts);
nd->dentry->d_mounted++;
}

+static void attach_prepare_mnt(struct vfsmount *mnt, struct nameidata *nd)
+{
+ mnt->mnt_parent = mntget(nd->mnt);
+ mnt->mnt_mountpoint = dget(nd->dentry);
+ nd->dentry->d_mounted++;
+}
+
+
+void do_attach_commit_mnt(struct vfsmount *mnt)
+{
+ struct vfsmount *parent = mnt->mnt_parent;
+ BUG_ON(parent==mnt);
+ if(list_empty(&mnt->mnt_hash))
+ list_add_tail(&mnt->mnt_hash,
+ mount_hashtable+hash(parent, mnt->mnt_mountpoint));
+ if(list_empty(&mnt->mnt_child))
+ list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
+ mnt->mnt_namespace = parent->mnt_namespace;
+ list_add_tail(&mnt->mnt_list, &mnt->mnt_namespace->list);
+}
+
+struct vfsmount *do_attach_prepare_mnt(struct vfsmount *mnt,
+ struct dentry *dentry,
+ struct vfsmount *template_mnt,
+ int clone_flag)
+{
+ struct vfsmount *child_mnt;
+ struct nameidata nd;
+
+ if (clone_flag) {
+ if(!(child_mnt = clone_mnt(template_mnt,
+ template_mnt->mnt_root)))
+ return NULL;
+ } else
+ child_mnt = template_mnt;
+
+ nd.mnt = mnt;
+ nd.dentry = dentry;
+
+ attach_prepare_mnt(child_mnt, &nd);
+
+ return child_mnt;
+}
+
+void do_detach_prepare_mnt(struct vfsmount *mnt, int free_flag)
+{
+ mnt->mnt_mountpoint->d_mounted--;
+ mntput(mnt->mnt_parent);
+ dput(mnt->mnt_mountpoint);
+ if (free_flag) {
+ BUG_ON(atomic_read(&mnt->mnt_count) != 1);
+ spin_lock(&vfsmount_lock);
+ list_del_init(&mnt->mnt_fslink);
+ spin_unlock(&vfsmount_lock);
+ mntput(mnt);
+ }
+}
+
static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root)
{
struct list_head *next = p->mnt_mounts.next;
@@ -149,29 +243,14 @@ static struct vfsmount *next_mnt(struct
return list_entry(next, struct vfsmount, mnt_child);
}

-static struct vfsmount *
-clone_mnt(struct vfsmount *old, struct dentry *root)
+static struct vfsmount *skip_mnt_tree(struct vfsmount *p)
{
- struct super_block *sb = old->mnt_sb;
- struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname);
-
- if (mnt) {
- mnt->mnt_flags = old->mnt_flags;
- atomic_inc(&sb->s_active);
- mnt->mnt_sb = sb;
- mnt->mnt_root = dget(root);
- mnt->mnt_mountpoint = mnt->mnt_root;
- mnt->mnt_parent = mnt;
- mnt->mnt_namespace = old->mnt_namespace;
-
- /* stick the duplicate mount on the same expiry list
- * as the original if that was on one */
- spin_lock(&vfsmount_lock);
- if (!list_empty(&old->mnt_fslink))
- list_add(&mnt->mnt_fslink, &old->mnt_fslink);
- spin_unlock(&vfsmount_lock);
+ struct list_head *prev = p->mnt_mounts.prev;
+ while (prev != &p->mnt_mounts) {
+ p = list_entry(prev, struct vfsmount, mnt_child);
+ prev = p->mnt_mounts.prev;
}
- return mnt;
+ return p;
}

void __mntput(struct vfsmount *mnt)
@@ -191,7 +270,7 @@ static void *m_start(struct seq_file *m,
struct list_head *p;
loff_t l = *pos;

- down_read(&n->sem);
+ down_read(&namespace_sem);
list_for_each(p, &n->list)
if (!l--)
return list_entry(p, struct vfsmount, mnt_list);
@@ -208,8 +287,7 @@ static void *m_next(struct seq_file *m,

static void m_stop(struct seq_file *m, void *v)
{
- struct namespace *n = m->private;
- up_read(&n->sem);
+ up_read(&namespace_sem);
}

static inline void mangle(struct seq_file *m, const char *s)
@@ -433,7 +511,7 @@ static int do_umount(struct vfsmount *mn
return retval;
}

- down_write(&current->namespace->sem);
+ down_write(&namespace_sem);
spin_lock(&vfsmount_lock);

if (atomic_read(&sb->s_active) == 1) {
@@ -455,7 +533,7 @@ static int do_umount(struct vfsmount *mn
spin_unlock(&vfsmount_lock);
if (retval)
security_sb_umount_busy(mnt);
- up_write(&current->namespace->sem);
+ up_write(&namespace_sem);
return retval;
}

@@ -495,9 +573,9 @@ out:
#ifdef __ARCH_WANT_SYS_OLDUMOUNT

/*
- * The 2.0 compatible umount. No flags.
+ * The 2.0 compatible umount. No flags.
*/
-
+
asmlinkage long sys_oldumount(char __user * name)
{
return sys_umount(name,0);
@@ -541,6 +619,9 @@ static struct vfsmount *copy_tree(struct
struct list_head *h;
struct nameidata nd;

+ if (IS_MNT_UNCLONE(mnt))
+ return NULL;
+
res = q = clone_mnt(mnt, dentry);
if (!q)
goto Enomem;
@@ -549,10 +630,15 @@ static struct vfsmount *copy_tree(struct
p = mnt;
for (h = mnt->mnt_mounts.next; h != &mnt->mnt_mounts; h = h->next) {
r = list_entry(h, struct vfsmount, mnt_child);
+
if (!lives_below_in_same_fs(r->mnt_mountpoint, dentry))
continue;

for (s = r; s; s = next_mnt(s, r)) {
+ if (IS_MNT_UNCLONE(s)) {
+ s = skip_mnt_tree(s);
+ continue;
+ }
while (p != s->mnt_parent) {
p = p->mnt_parent;
q = q->mnt_parent;
@@ -579,9 +665,276 @@ static struct vfsmount *copy_tree(struct
return NULL;
}

+/*
+ * return 1 if the mount tree contains a shared or slave mount
+ */
+static inline int tree_contains_sharedorslave(struct vfsmount *mnt)
+{
+ struct vfsmount *p;
+ for (p = mnt; p; p = next_mnt(p, mnt)) {
+ if (IS_MNT_SHARED(p) || IS_MNT_SLAVE(p))
+ return 1;
+ }
+ return 0;
+}
+
+/*
+ * commit the operations done in attach_recursive_mnt(). run through pnode list
+ * headed at 'pnodehead', and commit the operation done in
+ * attach_recursive_mnt();
+ */
+
+static void commit_attach_recursive_mnt(struct list_head *pnodehead)
+{
+ struct vfspnode *t_p, *tmp_pnode;
+
+ /*
+ * Merge or delete or slave each of the temporary pnode
+ */
+ spin_lock(&vfsmount_lock);
+ list_for_each_entry_safe(tmp_pnode, t_p, pnodehead,
+ pnode_peer_slave) {
+
+ int del_flag = IS_PNODE_DELETE(tmp_pnode);
+ int slave_flag = IS_PNODE_SLAVE(tmp_pnode);
+ struct vfspnode *master_pnode = tmp_pnode->pnode_master;
+
+ list_del_init(&tmp_pnode->pnode_peer_slave);
+ pnode_commit_mount(tmp_pnode, del_flag);
+
+ if (!del_flag && master_pnode) {
+ tmp_pnode->pnode_master = NULL;
+
+ if (slave_flag)
+ pnode_add_slave_pnode(master_pnode, tmp_pnode);
+ else
+ pnode_merge_pnode(tmp_pnode, master_pnode);
+
+ /*
+ * we don't need the extra reference to
+ * the master_pnode, which was created either
+ * (a) pnode_add_slave_pnode: when the mnt
+ * was made as a slave mnt.
+ * (b) pnode_merge_pnode: during clone_mnt().
+ */
+ put_pnode(master_pnode);
+ }
+ }
+ spin_unlock(&vfsmount_lock);
+}
+
+/*
+ * abort the operations done in attach_recursive_mnt(). run through the mount
+ * tree, till vfsmount 'last' and undo the changes. Ensure that all the mounts
+ * in the tree are all back in the mnt_list headed at 'source_mnt'.
+ * NOTE: This function is closely tied to the logic in
+ * 'attach_recursive_mnt()'
+ */
+static void abort_attach_recursive_mnt(struct vfsmount *source_mnt, struct
+ vfsmount *last, struct list_head *head) { struct vfsmount *p =
+ source_mnt, *m; struct vfspnode *src_pnode;
+
+ if (!last)
+ return;
+
+ do {
+ int is_unclone, is_pnode_slave;
+
+ m = p;
+ is_unclone = IS_MNT_UNCLONE(m);
+
+ BUG_ON(!m->mnt_pnode);
+
+ is_pnode_slave = IS_PNODE_SLAVE(m->mnt_pnode);
+ src_pnode = m->mnt_pnode->pnode_master;
+ m->mnt_pnode->pnode_master = NULL;
+ pnode_abort_mount(m->mnt_pnode, m);
+
+ m->mnt_pnode = src_pnode;
+ if (src_pnode) {
+ if(is_pnode_slave)
+ set_mnt_slave(m);
+ else
+ set_mnt_shared(m);
+ } else {
+ if (is_unclone)
+ set_mnt_unclone(m);
+ else
+ set_mnt_private(m);
+ }
+
+
+ list_add_tail(&m->mnt_list, head);
+ p = next_mnt(m, source_mnt);
+
+ } while ( p && m != last );
+ source_mnt->mnt_parent = source_mnt;
+ list_del_init(head);
+}
+
+ /*
+ * @source_mnt : mount tree to be attached
+ * @nd : place the mount tree @source_mnt is attached
+ *
+ * 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.
+ * ---------------------------------------------------------------------
+ * | BIND MOUNT OPERATION |
+ * |*******************************************************************|
+ * | dest --> | shared | private | slave |unclonable |
+ * | source | | | | |
+ * | | | | | | |
+ * | v | | | | |
+ * |*******************************************************************|
+ * | | | | | |
+ * | shared | shared (++) | shared (+)|shared (+)| shared (+)|
+ * | | | | | |
+ * | | | | | |
+ * | private | shared (+) | private | private | private |
+ * | | | | | |
+ * | | | | | |
+ * | slave | shared (+) | private | private | private |
+ * | | | | | |
+ * | | | | | |
+ * | unclonable| nomount | nomount | nomount | nomount |
+ * | | | | | |
+ * | | | | | |
+ * ********************************************************************
+ *
+ * (++) the mount will be 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
+ * and the new mount will be added to the source vfsmount's pnode.
+ *
+ * if the source mount is a tree, the operations explained above is
+ * applied to each vfsmount in the tree.
+ *
+ * Should be called without spinlocks held, because this function can sleep
+ * in allocations.
+ *
+ */
+static int attach_recursive_mnt(struct vfsmount *source_mnt,
+ struct nameidata *nd)
+{
+ struct vfsmount *mntpt_mnt, *last, *m, *p;
+ struct vfspnode *src_pnode, *dest_pnode, *tmp_pnode;
+ struct dentry *mntpt_dentry;
+ int ret;
+ LIST_HEAD(pnodehead);
+ LIST_HEAD(mnt_list_head);
+
+ /*
+ * if the source tree has no shared or slave mounts and
+ * the destination mount is not shared, fastpath.
+ */
+ mntpt_mnt = nd->mnt;
+ dest_pnode = IS_MNT_SHARED(mntpt_mnt) ? mntpt_mnt->mnt_pnode : NULL;
+ if (!dest_pnode && !tree_contains_sharedorslave(source_mnt)) {
+ spin_lock(&vfsmount_lock);
+ attach_mnt(source_mnt, nd);
+ list_add_tail(&mnt_list_head, &source_mnt->mnt_list);
+ list_splice(&mnt_list_head, mntpt_mnt->mnt_namespace->list.prev);
+ spin_unlock(&vfsmount_lock);
+ goto out;
+ }
+
+ /*
+ * Create temporary pnodes which shall hold all the new
+ * mounts. Merge or delete or slave that pnode later in a separate
+ * operation, depending on the type of source and destination mounts.
+ */
+ p = NULL;
+ last = NULL;
+ 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));
+
+ while (p && p != m->mnt_parent)
+ p = p->mnt_parent;
+
+ if (!p) {
+ mntpt_dentry = nd->dentry;
+ mntpt_mnt = nd->mnt;
+ } else {
+ mntpt_dentry = m->mnt_mountpoint;
+ mntpt_mnt = p;
+ }
+ p=m;
+
+ dest_pnode = IS_MNT_SHARED(mntpt_mnt) ?
+ mntpt_mnt->mnt_pnode : NULL;
+ src_pnode = (IS_MNT_SHARED(m))?
+ m->mnt_pnode : NULL;
+
+ /*
+ * get a temporary pnode into which add the new vfs, and keep
+ * track of these pnodes and their real pnode.
+ */
+ if (!(tmp_pnode = pnode_alloc())) {
+ ret = -ENOMEM;
+ goto error;
+ }
+
+ m->mnt_pnode = NULL;
+ list_del_init(&m->mnt_list);
+ list_add_tail(&tmp_pnode->pnode_peer_slave, &pnodehead);
+
+ if (dest_pnode) {
+ if ((ret = pnode_prepare_mount(dest_pnode, tmp_pnode,
+ mntpt_dentry, m, mntpt_mnt))) {
+ tmp_pnode->pnode_master = src_pnode;
+ m->mnt_pnode = tmp_pnode;
+ last = m;
+ goto error;
+ }
+ } 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);
+ /*
+ * 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().
+ */
+ m->mnt_pnode = tmp_pnode;
+ SET_PNODE_DELETE(tmp_pnode);
+ }
+ }
+
+ /*
+ * temporarily track the pnode with which the tmp_pnode
+ * has to merge with; in the pnode_master field.
+ */
+ tmp_pnode->pnode_master = src_pnode;
+ last = m;
+ }
+ commit_attach_recursive_mnt(&pnodehead);
+out:
+ mntget(source_mnt);
+ return 0;
+error:
+ /*
+ * ok we have errored out either because of memory exhaustion
+ * or something else not in our control. Gracefully return
+ * leaving no mess behind. Else it will haunt you. :(
+ */
+ abort_attach_recursive_mnt(source_mnt, last, &mnt_list_head);
+ return 1;
+}
+
static int graft_tree(struct vfsmount *mnt, struct nameidata *nd)
{
- int err;
+ int err, ret;
+
if (mnt->mnt_sb->s_flags & MS_NOUSER)
return -EINVAL;

@@ -599,17 +952,12 @@ static int graft_tree(struct vfsmount *m
goto out_unlock;

err = -ENOENT;
- spin_lock(&vfsmount_lock);
- if (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry)) {
- struct list_head head;

- attach_mnt(mnt, nd);
- list_add_tail(&head, &mnt->mnt_list);
- list_splice(&head, current->namespace->list.prev);
- mntget(mnt);
- err = 0;
- }
+ spin_lock(&vfsmount_lock);
+ ret = (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry));
spin_unlock(&vfsmount_lock);
+ if (ret)
+ err = attach_recursive_mnt(mnt, nd);
out_unlock:
up(&nd->dentry->d_inode->i_sem);
if (!err)
@@ -681,6 +1029,147 @@ static int do_make_unclone(struct vfsmou
return 0;
}

+ /*
+ * This operation is equivalent of mount --bind dir dir
+ * create a new mount at the dentry, and unmount all child mounts
+ * mounted on top of dentries below 'dentry', and mount them
+ * under the new mount.
+ */
+struct vfsmount *do_make_mounted(struct vfsmount *mnt, struct dentry *dentry)
+{
+ struct vfsmount *child_mnt, *next;
+ struct nameidata nd;
+ struct vfsmount *newmnt = clone_mnt(mnt, dentry);
+ LIST_HEAD(head);
+
+ /*
+ * note clone_mnt() gets a reference to the pnode.
+ * we won't use that pnode anyway. So just let it
+ * go
+ */
+ put_pnode(newmnt->mnt_pnode);
+ newmnt->mnt_pnode = NULL;
+
+ if (newmnt) {
+ /*
+ * walk through the mount list of mnt and move
+ * them under the new mount
+ */
+ spin_lock(&vfsmount_lock);
+ list_del_init(&newmnt->mnt_fslink);
+
+ list_for_each_entry_safe(child_mnt, next,
+ &mnt->mnt_mounts, mnt_child) {
+
+ if(child_mnt->mnt_mountpoint == dentry)
+ continue;
+
+ if(!is_subdir(child_mnt->mnt_mountpoint, dentry))
+ continue;
+
+ detach_mnt(child_mnt, &nd);
+ nd.mnt = newmnt;
+ attach_mnt(child_mnt, &nd);
+ }
+
+ nd.mnt = mnt;
+ nd.dentry = dentry;
+ attach_mnt(newmnt, &nd);
+ list_add_tail(&newmnt->mnt_list, &newmnt->mnt_namespace->list);
+ spin_unlock(&vfsmount_lock);
+ }
+ return newmnt;
+}
+
+ /*
+ * Inverse operation of do_make_mounted()
+ */
+int do_make_unmounted(struct vfsmount *mnt)
+{
+ struct vfsmount *parent_mnt, *child_mnt, *next;
+ struct nameidata nd;
+
+ /* validate if mount has a different parent */
+ parent_mnt = mnt->mnt_parent;
+ if (mnt == parent_mnt)
+ return 0;
+ /*
+ * cannot unmount a mount that is not created
+ * as a overlay mount.
+ */
+ if (mnt->mnt_mountpoint != mnt->mnt_root)
+ return -EINVAL;
+
+ /* for each submounts in the parent, put the mounts back */
+ spin_lock(&vfsmount_lock);
+ list_for_each_entry_safe(child_mnt, next, &mnt->mnt_mounts, mnt_child) {
+ detach_mnt(child_mnt, &nd);
+ nd.mnt = parent_mnt;
+ attach_mnt(child_mnt, &nd);
+ }
+ detach_mnt(mnt, &nd);
+ spin_unlock(&vfsmount_lock);
+ return 0;
+}
+
+/*
+ * @nd: contains the vfsmount and the dentry where the new mount
+ * is the be created
+ * @mnt: returns the newly created mount.
+ * Create a new mount at the location specified by 'nd' and
+ * propogate the mount to all other mounts if the mountpoint
+ * is under a shared mount.
+ */
+int make_mounted(struct nameidata *nd, struct vfsmount **mnt)
+{
+ struct vfsmount *parent_mnt;
+ struct dentry *parent_dentry;
+ int err = mount_is_safe(nd);
+ if (err)
+ return err;
+ parent_dentry = nd->dentry;
+ parent_mnt = nd->mnt;
+ /*
+ * check if dentry already has a vfsmount
+ * if it does not, create and attach
+ * a new vfsmount at that dentry.
+ * Also propogate the mount if parent_mnt
+ * is shared.
+ */
+ if(parent_dentry != parent_mnt->mnt_root) {
+ *mnt = IS_MNT_SHARED(parent_mnt) ?
+ pnode_make_mounted(parent_mnt->mnt_pnode,
+ parent_mnt, parent_dentry) :
+ do_make_mounted(parent_mnt, parent_dentry);
+ if (!*mnt)
+ err = -ENOMEM;
+ } else
+ *mnt = parent_mnt;
+ return err;
+}
+
+ /*
+ * Inverse operation of make_mounted()
+ */
+int make_unmounted(struct vfsmount *mnt)
+{
+ if (mnt == mnt->mnt_parent)
+ return 0;
+ /*
+ * cannot unmount a mount that is not created
+ * as a overlay mount.
+ */
+ if (mnt->mnt_mountpoint != mnt->mnt_root)
+ return -EINVAL;
+
+ if (IS_MNT_SHARED(mnt))
+ pnode_make_unmounted(mnt->mnt_pnode);
+ else
+ do_make_unmounted(mnt);
+
+ return 0;
+}
+
/*
* recursively change the type of the mountpoint.
*/
@@ -724,7 +1213,7 @@ static int do_change_type(struct nameida
static int do_loopback(struct nameidata *nd, char *old_name, int recurse)
{
struct nameidata old_nd;
- struct vfsmount *mnt = NULL;
+ struct vfsmount *mnt = NULL, *overlay_mnt=NULL;
int err = mount_is_safe(nd);
if (err)
return err;
@@ -734,14 +1223,31 @@ static int do_loopback(struct nameidata
if (err)
return err;

- down_write(&current->namespace->sem);
+ if (IS_MNT_UNCLONE(old_nd.mnt)) {
+ err = -EINVAL;
+ goto path_release;
+ }
+
+ down_write(&namespace_sem);
err = -EINVAL;
if (check_mnt(nd->mnt) && (!recurse || check_mnt(old_nd.mnt))) {
+
+ /*
+ * If the dentry is not the root dentry, and if a bind
+ * from a shared subtree is attempted, create a mount
+ * at the dentry, and use the new mount as the starting
+ * point for the bind/rbind operation.
+ */
+ overlay_mnt = old_nd.mnt;
+ if(IS_MNT_SHARED(old_nd.mnt) &&
+ (err = make_mounted(&old_nd, &overlay_mnt)))
+ goto out;
+
err = -ENOMEM;
if (recurse)
- mnt = copy_tree(old_nd.mnt, old_nd.dentry);
+ mnt = copy_tree(overlay_mnt, old_nd.dentry);
else
- mnt = clone_mnt(old_nd.mnt, old_nd.dentry);
+ mnt = clone_mnt(overlay_mnt, old_nd.dentry);
}

if (mnt) {
@@ -752,15 +1258,25 @@ static int do_loopback(struct nameidata

err = graft_tree(mnt, nd);
if (err) {
- spin_lock(&vfsmount_lock);
- umount_tree(mnt);
- spin_unlock(&vfsmount_lock);
- } else
- mntput(mnt);
- }
+ spin_lock(&vfsmount_lock);
+ umount_tree(mnt);
+ spin_unlock(&vfsmount_lock);
+ /*
+ * ok we failed! so undo any overlay
+ * mount that we did earlier.
+ */
+ if (old_nd.mnt != overlay_mnt)
+ make_unmounted(overlay_mnt);
+ } else
+ mntput(mnt);
+ }
+
+ out:
+ up_write(&namespace_sem);
+
+ path_release:
+ path_release(&old_nd);

- up_write(&current->namespace->sem);
- path_release(&old_nd);
return err;
}

@@ -808,7 +1324,7 @@ static int do_move_mount(struct nameidat
if (err)
return err;

- down_write(&current->namespace->sem);
+ down_write(&namespace_sem);
while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
;
err = -EINVAL;
@@ -852,7 +1368,7 @@ out2:
out1:
up(&nd->dentry->d_inode->i_sem);
out:
- up_write(&current->namespace->sem);
+ up_write(&namespace_sem);
if (!err)
path_release(&parent_nd);
path_release(&old_nd);
@@ -891,7 +1407,7 @@ int do_add_mount(struct vfsmount *newmnt
{
int err;

- down_write(&current->namespace->sem);
+ down_write(&namespace_sem);
/* Something was mounted here while we slept */
while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
;
@@ -920,7 +1436,7 @@ int do_add_mount(struct vfsmount *newmnt
}

unlock:
- up_write(&current->namespace->sem);
+ up_write(&namespace_sem);
mntput(newmnt);
return err;
}
@@ -976,7 +1492,7 @@ void mark_mounts_for_expiry(struct list_
get_namespace(namespace);

spin_unlock(&vfsmount_lock);
- down_write(&namespace->sem);
+ down_write(&namespace_sem);
spin_lock(&vfsmount_lock);

/* check that it is still dead: the count should now be 2 - as
@@ -1020,7 +1536,7 @@ void mark_mounts_for_expiry(struct list_
spin_unlock(&vfsmount_lock);
}

- up_write(&namespace->sem);
+ up_write(&namespace_sem);

mntput(mnt);
put_namespace(namespace);
@@ -1066,7 +1582,7 @@ int copy_mount_options(const void __user
int i;
unsigned long page;
unsigned long size;
-
+
*where = 0;
if (!data)
return 0;
@@ -1085,7 +1601,7 @@ int copy_mount_options(const void __user

i = size - exact_copy_from_user((void *)page, data, size);
if (!i) {
- free_page(page);
+ free_page(page);
return -EFAULT;
}
if (i != PAGE_SIZE)
@@ -1191,14 +1707,13 @@ int copy_namespace(int flags, struct tas
goto out;

atomic_set(&new_ns->count, 1);
- init_rwsem(&new_ns->sem);
INIT_LIST_HEAD(&new_ns->list);

- down_write(&tsk->namespace->sem);
+ down_write(&namespace_sem);
/* First pass: copy the tree topology */
new_ns->root = copy_tree(namespace->root, namespace->root->mnt_root);
if (!new_ns->root) {
- up_write(&tsk->namespace->sem);
+ up_write(&namespace_sem);
kfree(new_ns);
goto out;
}
@@ -1232,7 +1747,7 @@ int copy_namespace(int flags, struct tas
p = next_mnt(p, namespace->root);
q = next_mnt(q, new_ns->root);
}
- up_write(&tsk->namespace->sem);
+ up_write(&namespace_sem);

tsk->namespace = new_ns;

@@ -1414,7 +1929,7 @@ asmlinkage long sys_pivot_root(const cha
user_nd.mnt = mntget(current->fs->rootmnt);
user_nd.dentry = dget(current->fs->root);
read_unlock(&current->fs->lock);
- down_write(&current->namespace->sem);
+ down_write(&namespace_sem);
down(&old_nd.dentry->d_inode->i_sem);
error = -EINVAL;
if (!check_mnt(user_nd.mnt))
@@ -1460,7 +1975,7 @@ asmlinkage long sys_pivot_root(const cha
path_release(&parent_nd);
out2:
up(&old_nd.dentry->d_inode->i_sem);
- up_write(&current->namespace->sem);
+ up_write(&namespace_sem);
path_release(&user_nd);
path_release(&old_nd);
out1:
@@ -1487,7 +2002,6 @@ static void __init init_mount_tree(void)
panic("Can't allocate initial namespace");
atomic_set(&namespace->count, 1);
INIT_LIST_HEAD(&namespace->list);
- init_rwsem(&namespace->sem);
list_add(&mnt->mnt_list, &namespace->list);
namespace->root = mnt;
mnt->mnt_namespace = namespace;
@@ -1510,6 +2024,8 @@ void __init mnt_init(unsigned long mempa
unsigned int nr_hash;
int i;

+ init_rwsem(&namespace_sem);
+
mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount),
0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);

@@ -1557,7 +2073,7 @@ void __put_namespace(struct namespace *n
{
struct vfsmount *mnt;

- down_write(&namespace->sem);
+ down_write(&namespace_sem);
spin_lock(&vfsmount_lock);

list_for_each_entry(mnt, &namespace->list, mnt_list) {
@@ -1566,6 +2082,6 @@ void __put_namespace(struct namespace *n

umount_tree(namespace->root);
spin_unlock(&vfsmount_lock);
- up_write(&namespace->sem);
+ up_write(&namespace_sem);
kfree(namespace);
}
Index: 2.6.12.work2/fs/pnode.c
===================================================================
--- 2.6.12.work2.orig/fs/pnode.c
+++ 2.6.12.work2/fs/pnode.c
@@ -26,7 +26,6 @@
#include <asm/unistd.h>
#include <stdarg.h>

-
static kmem_cache_t * pnode_cachep;

/* spinlock for pnode related operations */
@@ -90,10 +89,12 @@ static void inline pnode_add_mnt(struct
mnt->mnt_pnode = pnode;
if (slave) {
set_mnt_slave(mnt);
- list_add(&mnt->mnt_pnode_mntlist, &pnode->pnode_slavevfs);
+ list_add(&mnt->mnt_pnode_mntlist,
+ &pnode->pnode_slavevfs);
} else {
set_mnt_shared(mnt);
- list_add(&mnt->mnt_pnode_mntlist, &pnode->pnode_vfs);
+ list_add(&mnt->mnt_pnode_mntlist,
+ &pnode->pnode_vfs);
}
get_pnode(pnode);
spin_unlock(&vfspnode_lock);
@@ -111,7 +112,6 @@ void pnode_add_slave_mnt(struct vfspnode
pnode_add_mnt(pnode, mnt, 1);
}

-
void pnode_add_slave_pnode(struct vfspnode *pnode,
struct vfspnode *slave_pnode)
{
@@ -439,3 +439,230 @@ error:
pnode_end(&context);
goto out;
}
+
+int pnode_mount_func(struct vfspnode *pnode, void *indata,
+ void **outdata, va_list args)
+{
+ struct vfspnode *pnode_slave, *pnode_master;
+ int ret=0;
+
+ pnode_master = indata;
+
+ if (*outdata)
+ pnode_slave = *outdata;
+ else if (!(pnode_slave = pnode_alloc()))
+ return -ENOMEM;
+
+ *outdata = pnode_slave;
+
+ if (pnode_slave && pnode_master)
+ pnode_add_slave_pnode(pnode_master, pnode_slave);
+ return ret;
+}
+
+int vfs_make_mounted_func(struct vfsmount *mnt, enum pnode_vfs_type flag,
+ void *indata, va_list args)
+{
+ struct dentry *target_dentry;
+ int ret=0;
+ struct vfsmount *child_mount;
+ struct vfspnode *pnode;
+
+ target_dentry = va_arg(args, struct dentry *);
+ if (!(child_mount = do_make_mounted(mnt, target_dentry))) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ pnode = (struct vfspnode *)indata;
+ switch (flag) {
+ case PNODE_SLAVE_VFS :
+ pnode_add_slave_mnt(pnode, child_mount);
+ break;
+ case PNODE_MEMBER_VFS :
+ pnode_add_member_mnt(pnode, child_mount);
+ break;
+ }
+
+out:
+ return ret;
+}
+
+/*
+ * @pnode: pnode that contains the vfsmounts, on which the
+ * new mount is created at dentry 'dentry'
+ * @dentry: the dentry on which the new mount is created
+ * @mnt: return the mount created on this vfsmount
+ * walk through all the vfsmounts belonging to this pnode
+ * as well as its slave pnodes and for each vfsmount create
+ * a new vfsmount at 'dentry'. Return the vfsmount created
+ * at 'dentry' of vfsmount 'mnt'.
+ */
+struct vfsmount *pnode_make_mounted(struct vfspnode *pnode,
+ struct vfsmount *mnt, struct dentry *dentry)
+{
+ struct vfsmount *child_mnt;
+ struct vfspnode *child_pnode;
+
+ if (!(child_pnode = pnode_alloc()))
+ return NULL;
+
+ if (pnode_traverse(pnode, child_pnode, (void *)NULL,
+ pnode_mount_func, NULL, vfs_make_mounted_func,
+ (void *)dentry))
+ goto error;
+ child_mnt = __lookup_mnt(mnt, dentry, dentry);
+ mntput(child_mnt);
+ return child_mnt;
+
+error:
+ pnode_make_unmounted(child_pnode);
+ return NULL;
+}
+
+int vfs_make_unmounted_func(struct vfsmount *mnt, enum pnode_vfs_type flag,
+ void *indata, va_list args)
+{
+ struct vfspnode *pnode;
+ int ret=0;
+
+ if (do_make_unmounted(mnt)) {
+ ret = 1;
+ goto out;
+ }
+
+ pnode = mnt->mnt_pnode;
+ spin_lock(&vfspnode_lock);
+ list_del_init(&mnt->mnt_pnode_mntlist);
+ put_pnode_locked(pnode);
+ spin_unlock(&vfspnode_lock);
+out:
+ return ret;
+}
+
+int pnode_make_unmounted(struct vfspnode *pnode)
+{
+ return pnode_traverse(pnode, NULL, (void *)NULL,
+ NULL, NULL, vfs_make_unmounted_func);
+}
+
+int vfs_prepare_mount_func(struct vfsmount *mnt, enum pnode_vfs_type flag,
+ void *indata, va_list args)
+{
+ struct vfsmount *source_mnt, *child_mnt, *p_mnt;
+ struct dentry *mountpoint_dentry;
+ struct vfspnode *pnode = (struct vfspnode *)indata;
+
+ source_mnt = va_arg(args, struct vfsmount * );
+ mountpoint_dentry = va_arg(args, struct dentry *);
+ p_mnt = va_arg(args, struct vfsmount *);
+
+ if ((p_mnt != mnt) || (source_mnt == source_mnt->mnt_parent)) {
+ child_mnt = do_attach_prepare_mnt(mnt, mountpoint_dentry,
+ source_mnt, (p_mnt != mnt));
+ if (!child_mnt)
+ return -ENOMEM;
+
+ if (child_mnt != source_mnt)
+ put_pnode(source_mnt->mnt_pnode);
+ } else
+ child_mnt = source_mnt;
+
+ switch (flag) {
+ case PNODE_SLAVE_VFS :
+ pnode_add_slave_mnt(pnode, child_mnt);
+ break;
+ case PNODE_MEMBER_VFS :
+ pnode_add_member_mnt(pnode, child_mnt);
+ break;
+ }
+
+ return 0;
+}
+
+int pnode_prepare_mount(struct vfspnode *pnode,
+ struct vfspnode *master_child_pnode,
+ struct dentry *mountpoint_dentry,
+ struct vfsmount *source_mnt,
+ struct vfsmount *mnt)
+{
+ return pnode_traverse(pnode,
+ master_child_pnode,
+ (void *)NULL,
+ pnode_mount_func,
+ NULL,
+ vfs_prepare_mount_func,
+ source_mnt,
+ mountpoint_dentry,
+ mnt);
+}
+
+int pnode_commit_mount_post_func(struct vfspnode *pnode, void *indata,
+ va_list args)
+{
+ if (va_arg(args, int)) {
+ spin_lock(&vfspnode_lock);
+ BUG_ON(!list_empty(&pnode->pnode_vfs));
+ BUG_ON(!list_empty(&pnode->pnode_slavevfs));
+ BUG_ON(!list_empty(&pnode->pnode_slavepnode));
+ list_del_init(&pnode->pnode_peer_slave);
+ put_pnode_locked(pnode);
+ spin_unlock(&vfspnode_lock);
+ }
+ return 0;
+}
+
+int vfs_commit_mount_func(struct vfsmount *mnt, enum pnode_vfs_type flag,
+ void *indata, va_list args)
+{
+ BUG_ON(mnt == mnt->mnt_parent);
+ do_attach_commit_mnt(mnt);
+ if (va_arg(args, int)) {
+ spin_lock(&vfspnode_lock);
+ list_del_init(&mnt->mnt_pnode_mntlist);
+ put_pnode_locked(mnt->mnt_pnode);
+ spin_unlock(&vfspnode_lock);
+ mnt->mnt_pnode = NULL;
+ }
+ return 0;
+}
+
+/*
+ * @pnode: walk the propogation tree and complete the
+ * attachments of the child mounts to the parents
+ * correspondingly.
+ * @flag: if set destroy the propogation tree
+ */
+int pnode_commit_mount(struct vfspnode *pnode, int flag)
+{
+ return pnode_traverse(pnode,
+ NULL, (void *)NULL, NULL, pnode_commit_mount_post_func,
+ vfs_commit_mount_func, flag);
+}
+
+int vfs_abort_mount_func(struct vfsmount *mnt,
+ enum pnode_vfs_type flag, void *indata, va_list args)
+
+{
+ struct vfsmount *exception_mnt = va_arg(args, struct vfsmount *);
+ BUG_ON(!mnt->mnt_pnode);
+ pnode_disassociate_mnt(mnt);
+ do_detach_prepare_mnt(mnt, (exception_mnt != mnt));
+ return 0;
+}
+
+/*
+ * clean the propogation tree under pnode, releasing all
+ * the mounts, except exception_mnt
+ * @pnode: the pnode tree to be cleanup unlinking and
+ * releasing all pnodes in the tree as well as
+ * unlinking any mounts, except 'exception_mnt'
+ * @exception_mnt: the mnt to be unlinked from pnode
+ * bug not released.
+ */
+int pnode_abort_mount(struct vfspnode *pnode,
+ struct vfsmount *exception_mnt)
+{
+ return pnode_traverse(pnode,
+ NULL, (void *)NULL, NULL, NULL,
+ vfs_abort_mount_func, exception_mnt);
+}
Index: 2.6.12.work2/include/linux/fs.h
===================================================================
--- 2.6.12.work2.orig/include/linux/fs.h
+++ 2.6.12.work2/include/linux/fs.h
@@ -1216,7 +1216,12 @@ extern struct vfsmount *kern_mount(struc
extern int may_umount_tree(struct vfsmount *);
extern int may_umount(struct vfsmount *);
extern long do_mount(char *, char *, char *, unsigned long, void *);
+extern struct vfsmount *do_attach_prepare_mnt(struct vfsmount *,
+ struct dentry *, struct vfsmount *, int);
+extern void do_attach_commit_mnt(struct vfsmount *);
extern struct vfsmount *do_make_mounted(struct vfsmount *, struct dentry *);
+extern int do_make_unmounted(struct vfsmount *);
+extern void do_detach_prepare_mnt(struct vfsmount *, int);

extern int vfs_statfs(struct super_block *, struct kstatfs *);

Index: 2.6.12.work2/include/linux/namespace.h
===================================================================
--- 2.6.12.work2.orig/include/linux/namespace.h
+++ 2.6.12.work2/include/linux/namespace.h
@@ -9,7 +9,6 @@ struct namespace {
atomic_t count;
struct vfsmount * root;
struct list_head list;
- struct rw_semaphore sem;
};

extern void umount_tree(struct vfsmount *);
Index: 2.6.12.work2/include/linux/dcache.h
===================================================================
--- 2.6.12.work2.orig/include/linux/dcache.h
+++ 2.6.12.work2/include/linux/dcache.h
@@ -329,6 +329,8 @@ static inline int d_mountpoint(struct de
}

extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *);
+extern struct vfsmount *__lookup_mnt(struct vfsmount *,
+ struct dentry *, struct dentry *);
extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);

extern int sysctl_vfs_cache_pressure;