[RFC PATCH 3/8] bind/rbind a shared/private/slave/unclone tree

From: Ram
Date: Fri Jul 08 2005 - 05:49:56 EST

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

RP

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

RP

Signed by Ram Pai (linuxram@xxxxxxxxxx)

fs/namespace.c | 510 ++++++++++++++++++++++++++++++++++++++++----------
fs/pnode.c | 244 +++++++++++++++++++++++
include/linux/fs.h | 4
include/linux/pnode.h | 5
4 files changed, 664 insertions(+), 99 deletions(-)

Index: 2.6.12/fs/namespace.c
===================================================================
--- 2.6.12.orig/fs/namespace.c
+++ 2.6.12/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);
@@ -109,6 +110,32 @@ struct vfsmount *lookup_mnt(struct vfsmo
return found;
}

+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;
@@ -122,7 +149,6 @@ static void detach_mnt(struct vfsmount *
mnt->mnt_mountpoint = mnt->mnt_root;
list_del_init(&mnt->mnt_child);
list_del_init(&mnt->mnt_hash);
- list_del_init(&mnt->mnt_pnode_mntlist);
old_nd->dentry->d_mounted--;
}

@@ -130,11 +156,68 @@ static void attach_mnt(struct vfsmount *
{
mnt->mnt_parent = mntget(nd->mnt);
mnt->mnt_mountpoint = dget(nd->dentry);
+ mnt->mnt_namespace = nd->mnt->mnt_namespace;
list_add(&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 struct vfsmount *do_attach_mnt(struct vfsmount *mnt,
+ struct dentry *dentry,
+ struct vfsmount *child_mnt)
+{
+ struct nameidata nd;
+ LIST_HEAD(head);
+
+ nd.mnt = mnt;
+ nd.dentry = dentry;
+ attach_mnt(child_mnt, &nd);
+ list_add_tail(&head, &child_mnt->mnt_list);
+ list_splice(&head, child_mnt->mnt_namespace->list.prev);
+ return child_mnt;
+}
+
+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_real_mnt(struct vfsmount *mnt)
+{
+ struct vfsmount *parent = mnt->mnt_parent;
+ BUG_ON(parent==mnt);
+ if(list_empty(&mnt->mnt_hash))
+ list_add(&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)
+ child_mnt = clone_mnt(template_mnt, template_mnt->mnt_root);
+ else
+ child_mnt = template_mnt;
+
+ nd.mnt = mnt;
+ nd.dentry = dentry;
+
+ attach_prepare_mnt(child_mnt, &nd);
+
+ return child_mnt;
+}
+
static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root)
{
struct list_head *next = p->mnt_mounts.next;
@@ -151,37 +234,20 @@ 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;
- 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);
+ 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)
{
struct super_block *sb = mnt->mnt_sb;
dput(mnt->mnt_root);
- put_pnode(mnt->mnt_pnode);
free_vfsmnt(mnt);
deactivate_super(sb);
}
@@ -195,7 +261,7 @@ 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);
@@ -212,8 +278,7 @@ 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)
@@ -437,7 +502,7 @@ 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) {
@@ -459,7 +524,7 @@ 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;
}

@@ -499,9 +564,9 @@ 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);
@@ -545,6 +610,9 @@ static struct vfsmount *copy_tree(struct
struct list_head *h;
struct nameidata nd;

+ if (IS_MNT_UNCLONABLE(mnt))
+ return NULL;
+
res = q = clone_mnt(mnt, dentry);
if (!q)
goto Enomem;
@@ -553,10 +621,15 @@ 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_UNCLONABLE(s)) {
+ s = skip_mnt_tree(s);
+ continue;
+ }
while (p != s->mnt_parent) {
p = p->mnt_parent;
q = q->mnt_parent;
@@ -583,9 +656,163 @@ static struct vfsmount *copy_tree(struct
return NULL;
}

+ /*
+ * @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| - | - | - | - |
+ * | | | | | |
+ * | | | | | |
+ * ***************************************************************************
+ *
+ * (++) 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 void
+attach_recursive_mnt(struct vfsmount *source_mnt, struct nameidata *nd)
+{
+ struct vfsmount *mntpt_mnt, *m, *p;
+ struct vfspnode *src_pnode, *t_p, *dest_pnode, *tmp_pnode;
+ struct dentry *mntpt_dentry;
+ LIST_HEAD(pnodehead);
+
+ mntpt_mnt = nd->mnt;
+ dest_pnode = IS_MNT_SHARED(mntpt_mnt) ? mntpt_mnt->mnt_pnode : NULL;
+ src_pnode = IS_MNT_SHARED(source_mnt) ? source_mnt->mnt_pnode : NULL;
+
+ if (!dest_pnode && !src_pnode) {
+ LIST_HEAD(head);
+ spin_lock(&vfsmount_lock);
+ do_attach_mnt(nd->mnt, nd->dentry, source_mnt);
+ spin_unlock(&vfsmount_lock);
+ goto out;
+ }
+
+ /*
+ * Ok, the source or the destination pnode exists.
+ * Get ready for pnode operations.
+ * Create a temporary pnode 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;
+ for (m = source_mnt; m; m = next_mnt(m, source_mnt)) {
+ int unclone = IS_MNT_UNCLONABLE(m);
+
+ list_del_init(&m->mnt_list);
+
+ 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;
+
+ m->mnt_pnode = NULL;
+ /*
+ * get a temporary pnode into which add the new vfs, and keep
+ * track of these pnodes and their real pnode.
+ */
+ while (!(tmp_pnode = pnode_alloc()))
+ schedule();
+
+
+ if (dest_pnode && !unclone)
+ pnode_prepare_mount(dest_pnode, tmp_pnode,
+ mntpt_dentry, m, mntpt_mnt);
+ else {
+ if (m == m->mnt_parent)
+ do_attach_prepare_mnt(mntpt_mnt,
+ mntpt_dentry, m, 0);
+ pnode_add_member_mnt(tmp_pnode, m);
+ if (unclone)
+ SET_MNT_UNCLONABLE(m);
+ }
+
+ if ((!src_pnode && !dest_pnode) || unclone)
+ SET_PNODE_DELETE(tmp_pnode);
+ tmp_pnode->pnode_master = src_pnode;
+ /*
+ * temporarily track the pnode with which the tmp_pnode
+ * has to merge with; in the pnode_master field.
+ */
+ list_add_tail(&tmp_pnode->pnode_peer_slave, &pnodehead);
+ }
+
+ /*
+ * new mounts. Merge or delete or slave 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);
+ struct vfspnode *master_pnode = tmp_pnode->pnode_master;
+ list_del_init(&tmp_pnode->pnode_peer_slave);
+ pnode_real_mount(tmp_pnode, del_flag);
+ if (!del_flag && master_pnode) {
+ tmp_pnode->pnode_master = NULL;
+ pnode_merge_pnode(tmp_pnode, master_pnode);
+ /*
+ * we don't need the extra reference to
+ * the master_pnode, that 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);
+out:
+ mntget(source_mnt);
+ return;
+}
+
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;

@@ -603,17 +830,14 @@ 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);
+ spin_lock(&vfsmount_lock);
+ ret = (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry));
+ spin_unlock(&vfsmount_lock);
+ if (ret) {
+ attach_recursive_mnt(mnt, nd);
err = 0;
}
- spin_unlock(&vfsmount_lock);
out_unlock:
up(&nd->dentry->d_inode->i_sem);
if (!err)
@@ -621,6 +845,11 @@ out_unlock:
return err;
}

+ /*
+ * create a new mount at the dentry, and move all child mounts
+ * underneath it, if those mounts were below the dentry on the
+ * parent mount.
+ */
struct vfsmount *do_make_mounted(struct vfsmount *mnt, struct dentry *dentry)
{
struct vfsmount *child_mnt, *next;
@@ -628,6 +857,14 @@ struct vfsmount *do_make_mounted(struct
struct vfsmount *newmnt = clone_mnt(mnt, dentry);
LIST_HEAD(move);

+ /*
+ * 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) {
/* put in code for mount expiry */
/* TOBEDONE */
@@ -653,14 +890,41 @@ struct vfsmount *do_make_mounted(struct

nd.mnt = mnt;
nd.dentry = dentry;
- attach_mnt(newmnt, &nd);
+ do_attach_mnt(nd.mnt, nd.dentry, newmnt);
spin_unlock(&vfsmount_lock);
}
return newmnt;
}

-int
-_do_make_mounted(struct nameidata *nd, struct vfsmount **mnt)
+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;
+}
+
+int make_mounted(struct nameidata *nd, struct vfsmount **mnt)
{
struct vfsmount *parent_mnt;
struct dentry *parent_dentry;
@@ -671,9 +935,10 @@ _do_make_mounted(struct nameidata *nd, s
parent_mnt = nd->mnt;
/*
* check if dentry already has a vfsmount
- * if it does not, create a vfsmount there.
- * which means you need to propogate it
- * across all vfsmounts.
+ * 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 = parent_mnt;
@@ -688,6 +953,25 @@ _do_make_mounted(struct nameidata *nd, s
return err;
}

+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.
*/
@@ -702,7 +986,7 @@ static int do_change_type(struct nameida
&& !(flag & MS_SLAVE))
return -EINVAL;

- if ((err = _do_make_mounted(nd, &mnt)))
+ if ((err = make_mounted(nd, &mnt)))
return err;

spin_lock(&vfsmount_lock);
@@ -735,9 +1019,8 @@ static int do_change_type(struct nameida
break;

case MS_SLAVE:
- if (IS_MNT_SLAVE(m)) {
+ if (IS_MNT_SLAVE(m))
break;
- }
/*
* only shared mounts can
* be made slave
@@ -775,7 +1058,7 @@ 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;
@@ -785,14 +1068,31 @@ static int do_loopback(struct nameidata
if (err)
return err;

- down_write(&current->namespace->sem);
+ if (IS_MNT_UNCLONABLE(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) {
@@ -803,15 +1103,25 @@ 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;
}

@@ -859,7 +1169,7 @@ 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;
@@ -903,7 +1213,7 @@ 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);
@@ -942,7 +1252,7 @@ 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))
;
@@ -971,7 +1281,7 @@ int do_add_mount(struct vfsmount *newmnt
}

unlock:
- up_write(&current->namespace->sem);
+ up_write(&namespace_sem);
mntput(newmnt);
return err;
}
@@ -1027,7 +1337,7 @@ 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
@@ -1071,7 +1381,7 @@ void mark_mounts_for_expiry(struct list_
spin_unlock(&vfsmount_lock);
}

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

mntput(mnt);
put_namespace(namespace);
@@ -1117,7 +1427,7 @@ int copy_mount_options(const void __user
int i;
unsigned long page;
unsigned long size;
-
+
*where = 0;
if (!data)
return 0;
@@ -1136,7 +1446,7 @@ 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)
@@ -1242,14 +1552,13 @@ 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;
}
@@ -1283,7 +1592,7 @@ 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;

@@ -1465,7 +1774,7 @@ 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))
@@ -1511,7 +1820,7 @@ 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:
@@ -1538,7 +1847,6 @@ 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;
@@ -1561,6 +1869,8 @@ 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);

@@ -1608,7 +1918,7 @@ 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) {
@@ -1617,6 +1927,6 @@ 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/fs/pnode.c
===================================================================
--- 2.6.12.orig/fs/pnode.c
+++ 2.6.12/fs/pnode.c
@@ -287,6 +287,52 @@ pnode_disassociate_mnt(struct vfsmount *
mnt->mnt_flags &= ~MNT_SHARED;
}

+// merge pnode into peer_pnode and get rid of pnode
+int
+pnode_merge_pnode(struct vfspnode *pnode, struct vfspnode *peer_pnode)
+{
+ struct vfspnode *slave_pnode, *pnext;
+ struct vfsmount *mnt, *slave_mnt, *next;
+ int i,count;
+
+ spin_lock(&vfspnode_lock);
+ list_for_each_entry_safe(slave_pnode, pnext,
+ &pnode->pnode_slavepnode, pnode_peer_slave) {
+ slave_pnode->pnode_master = peer_pnode;
+ list_move(&slave_pnode->pnode_peer_slave,
+ &peer_pnode->pnode_slavepnode);
+ }
+
+ list_for_each_entry_safe(slave_mnt, next,
+ &pnode->pnode_slavevfs, mnt_pnode_mntlist) {
+ slave_mnt->mnt_pnode = peer_pnode;
+ list_move(&slave_mnt->mnt_pnode_mntlist,
+ &peer_pnode->pnode_slavevfs);
+ }
+
+ list_for_each_entry_safe(mnt, next,
+ &pnode->pnode_vfs, mnt_pnode_mntlist) {
+ mnt->mnt_pnode = peer_pnode;
+ list_move(&mnt->mnt_pnode_mntlist,
+ &peer_pnode->pnode_vfs);
+ }
+
+ count = atomic_read(&pnode->pnode_count);
+ atomic_add(count, &peer_pnode->pnode_count);
+ spin_unlock(&vfspnode_lock);
+
+ /*
+ * delete all references to 'pnode'.
+ * A better implementation can simply
+ * call free_pnode(pnode). But this is
+ * a cleaner way of doing it. Offcourse
+ * with some cost.
+ */
+ for (i=0 ; i <count; i++)
+ put_pnode(pnode);
+ return 0;
+}
+
struct vfsmount *
pnode_make_mounted(struct vfspnode *pnode, struct vfsmount *mnt, struct dentry *dentry)
{
@@ -360,3 +406,223 @@ out:
mntput(child_mnt);
return child_mnt;
}
+
+int
+vfs_make_unmounted(struct vfsmount *mnt)
+{
+ struct vfspnode *pnode;
+ int ret=0;
+
+ if (do_make_unmounted(mnt)) {
+ ret = 1;
+ goto out;
+ }
+ pnode = mnt->mnt_pnode;
+ list_del_init(&mnt->mnt_pnode_mntlist);
+ put_pnode(pnode);
+out:
+ return ret;
+}
+
+int
+pnode_make_unmounted(struct vfspnode *pnode)
+{
+ int ret=0,traversal;
+ struct vfsmount *slave_mnt, *member_mnt, *t_m;
+ struct pcontext context;
+
+ context.start = pnode;
+ context.pnode = NULL;
+ while(pnode_next(&context)) {
+ traversal = context.traversal;
+ pnode = context.pnode;
+ if(traversal == PNODE_UP) {
+ // traverse member vfsmounts
+ spin_lock(&vfspnode_lock);
+ list_for_each_entry_safe(member_mnt,
+ t_m, &pnode->pnode_vfs, mnt_pnode_mntlist) {
+ spin_unlock(&vfspnode_lock);
+ if ((ret = vfs_make_unmounted(member_mnt)))
+ goto out;
+ spin_lock(&vfspnode_lock);
+ }
+ list_for_each_entry_safe(slave_mnt,
+ t_m, &pnode->pnode_slavevfs, mnt_pnode_mntlist) {
+ spin_unlock(&vfspnode_lock);
+ if ((ret = vfs_make_unmounted(slave_mnt)))
+ goto out;
+ spin_lock(&vfspnode_lock);
+ }
+ spin_unlock(&vfspnode_lock);
+ }
+ }
+
+out:
+ return ret;
+}
+
+
+int
+vfs_prepare_mount_func(struct vfsmount *mnt, int flag, struct vfspnode *pnode,
+ struct vfsmount *source_mnt,
+ struct dentry *mountpoint_dentry,
+ struct vfsmount *p_mnt)
+
+{
+ struct vfsmount *child_mnt;
+
+ 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 != 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)
+{
+ int ret=0,traversal,level;
+ struct vfspnode *slave_pnode, *master_pnode, *slave_child_pnode, *child_pnode;
+ struct vfsmount *slave_mnt, *member_mnt, *t_m;
+ struct pcontext context;
+ static struct inoutdata p_array[PNODE_MAX_SLAVE_LEVEL];
+
+ context.start = pnode;
+ context.pnode = NULL;
+ while(pnode_next(&context)) {
+ traversal = context.traversal;
+ level = context.level;
+ pnode = context.pnode;
+ slave_pnode = context.slave_pnode;
+ master_pnode = context.master_pnode;
+
+ if (traversal == PNODE_DOWN ) {
+
+ child_pnode = NULL;
+ if (!master_pnode)
+ child_pnode = master_child_pnode;
+
+ while (!(child_pnode = pnode_alloc()))
+ schedule();
+
+ p_array[level].my_data = child_pnode;
+
+ } else if(traversal == PNODE_MID) {
+
+ child_pnode = (struct vfspnode *)p_array[level].my_data;
+ slave_child_pnode = p_array[level+1].out_data;
+ pnode_add_slave_pnode(child_pnode, slave_child_pnode);
+
+ } else if(traversal == PNODE_UP) {
+
+ child_pnode = p_array[level].my_data;
+ spin_lock(&vfspnode_lock);
+ list_for_each_entry_safe(member_mnt,
+ t_m, &pnode->pnode_vfs, mnt_pnode_mntlist) {
+ spin_unlock(&vfspnode_lock);
+ if((ret=vfs_prepare_mount_func(member_mnt,
+ PNODE_MEMBER_VFS, child_pnode, source_mnt,
+ mountpoint_dentry, mnt)))
+ goto out;
+ spin_lock(&vfspnode_lock);
+ }
+ list_for_each_entry_safe(slave_mnt,
+ t_m, &pnode->pnode_slavevfs, mnt_pnode_mntlist) {
+ spin_unlock(&vfspnode_lock);
+ if((ret = vfs_prepare_mount_func(slave_mnt,
+ PNODE_SLAVE_VFS, child_pnode, source_mnt,
+ mountpoint_dentry, mnt)))
+ goto out;
+ spin_lock(&vfspnode_lock);
+ }
+ spin_unlock(&vfspnode_lock);
+ p_array[level].out_data = child_pnode;
+
+ }
+ }
+
+out:
+ return ret;
+}
+
+
+int
+vfs_real_mount_func(struct vfsmount *mnt, int delflag)
+{
+ BUG_ON(mnt == mnt->mnt_parent);
+ do_attach_real_mnt(mnt);
+ if (delflag) {
+ list_del_init(&mnt->mnt_pnode_mntlist);
+ mnt->mnt_pnode = NULL;
+ SET_MNT_PRIVATE(mnt);
+ }
+ 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_real_mount(struct vfspnode *pnode, int flag)
+{
+ int ret=0,traversal;
+ struct vfsmount *slave_mnt, *member_mnt, *t_m;
+ struct pcontext context;
+
+ context.start = pnode;
+ context.pnode = NULL;
+ while(pnode_next(&context)) {
+ traversal = context.traversal;
+ pnode = context.pnode;
+ if(traversal == PNODE_MID) {
+ if (flag) {
+ 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(pnode);
+ }
+ } else if(traversal == PNODE_UP) {
+ // traverse member vfsmounts
+ spin_lock(&vfspnode_lock);
+ list_for_each_entry_safe(member_mnt,
+ t_m, &pnode->pnode_vfs, mnt_pnode_mntlist) {
+ spin_unlock(&vfspnode_lock);
+ if ((ret = vfs_real_mount_func(member_mnt, flag)))
+ goto out;
+ }
+ list_for_each_entry_safe(slave_mnt,
+ t_m, &pnode->pnode_slavevfs, mnt_pnode_mntlist) {
+ spin_unlock(&vfspnode_lock);
+ if ((ret = vfs_real_mount_func(slave_mnt, flag)))
+ goto out;
+ spin_lock(&vfspnode_lock);
+ }
+ spin_unlock(&vfspnode_lock);
+ }
+ }
+
+out:
+ return ret;
+}
Index: 2.6.12/include/linux/fs.h
===================================================================
--- 2.6.12.orig/include/linux/fs.h
+++ 2.6.12/include/linux/fs.h
@@ -1216,7 +1216,11 @@ 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_real_mnt(struct vfsmount *);
extern struct vfsmount *do_make_mounted(struct vfsmount *, struct dentry *);
+extern int do_make_unmounted(struct vfsmount *);

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

Index: 2.6.12/include/linux/pnode.h
===================================================================
--- 2.6.12.orig/include/linux/pnode.h
+++ 2.6.12/include/linux/pnode.h
@@ -73,6 +73,11 @@ void pnode_del_slave_mnt(struct vfsmount
void pnode_del_member_mnt(struct vfsmount *);
void pnode_disassociate_mnt(struct vfsmount *);
void pnode_add_slave_pnode(struct vfspnode *, struct vfspnode *);
+int pnode_merge_pnode(struct vfspnode *, struct vfspnode *);
struct vfsmount * pnode_make_mounted(struct vfspnode *, struct vfsmount *, struct dentry *);
+int pnode_make_unmounted(struct vfspnode *);
+int pnode_prepare_mount(struct vfspnode *, struct vfspnode *, struct dentry *,
+ struct vfsmount *, struct vfsmount *);
+int pnode_real_mount(struct vfspnode *, int);
#endif /* KERNEL */
#endif /* _LINUX_PNODE_H */
Index: 2.6.12/include/linux/namespace.h
===================================================================
--- 2.6.12.orig/include/linux/namespace.h
+++ 2.6.12/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 *);