linux-hardened/fs/pnode.c
Andi Kleen 962830df36 brlocks/lglocks: API cleanups
lglocks and brlocks are currently generated with some complicated macros
in lglock.h.  But there's no reason to not just use common utility
functions and put all the data into a common data structure.

In preparation, this patch changes the API to look more like normal
function calls with pointers, not magic macros.

The patch is rather large because I move over all users in one go to keep
it bisectable.  This impacts the VFS somewhat in terms of lines changed.
But no actual behaviour change.

[akpm@linux-foundation.org: checkpatch fixes]
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-05-29 23:28:41 -04:00

355 lines
8.8 KiB
C

/*
* linux/fs/pnode.c
*
* (C) Copyright IBM Corporation 2005.
* Released under GPL v2.
* Author : Ram Pai (linuxram@us.ibm.com)
*
*/
#include <linux/mnt_namespace.h>
#include <linux/mount.h>
#include <linux/fs.h>
#include "internal.h"
#include "pnode.h"
/* return the next shared peer mount of @p */
static inline struct mount *next_peer(struct mount *p)
{
return list_entry(p->mnt_share.next, struct mount, mnt_share);
}
static inline struct mount *first_slave(struct mount *p)
{
return list_entry(p->mnt_slave_list.next, struct mount, mnt_slave);
}
static inline struct mount *next_slave(struct mount *p)
{
return list_entry(p->mnt_slave.next, struct mount, mnt_slave);
}
static struct mount *get_peer_under_root(struct mount *mnt,
struct mnt_namespace *ns,
const struct path *root)
{
struct mount *m = mnt;
do {
/* Check the namespace first for optimization */
if (m->mnt_ns == ns && is_path_reachable(m, m->mnt.mnt_root, root))
return m;
m = next_peer(m);
} while (m != mnt);
return NULL;
}
/*
* Get ID of closest dominating peer group having a representative
* under the given root.
*
* Caller must hold namespace_sem
*/
int get_dominating_id(struct mount *mnt, const struct path *root)
{
struct mount *m;
for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) {
struct mount *d = get_peer_under_root(m, mnt->mnt_ns, root);
if (d)
return d->mnt_group_id;
}
return 0;
}
static int do_make_slave(struct mount *mnt)
{
struct mount *peer_mnt = mnt, *master = mnt->mnt_master;
struct mount *slave_mnt;
/*
* slave 'mnt' to a peer mount that has the
* same root dentry. If none is available then
* slave it to anything that is available.
*/
while ((peer_mnt = next_peer(peer_mnt)) != mnt &&
peer_mnt->mnt.mnt_root != mnt->mnt.mnt_root) ;
if (peer_mnt == mnt) {
peer_mnt = next_peer(mnt);
if (peer_mnt == mnt)
peer_mnt = NULL;
}
if (IS_MNT_SHARED(mnt) && list_empty(&mnt->mnt_share))
mnt_release_group_id(mnt);
list_del_init(&mnt->mnt_share);
mnt->mnt_group_id = 0;
if (peer_mnt)
master = peer_mnt;
if (master) {
list_for_each_entry(slave_mnt, &mnt->mnt_slave_list, mnt_slave)
slave_mnt->mnt_master = master;
list_move(&mnt->mnt_slave, &master->mnt_slave_list);
list_splice(&mnt->mnt_slave_list, master->mnt_slave_list.prev);
INIT_LIST_HEAD(&mnt->mnt_slave_list);
} else {
struct list_head *p = &mnt->mnt_slave_list;
while (!list_empty(p)) {
slave_mnt = list_first_entry(p,
struct mount, mnt_slave);
list_del_init(&slave_mnt->mnt_slave);
slave_mnt->mnt_master = NULL;
}
}
mnt->mnt_master = master;
CLEAR_MNT_SHARED(mnt);
return 0;
}
/*
* vfsmount lock must be held for write
*/
void change_mnt_propagation(struct mount *mnt, int type)
{
if (type == MS_SHARED) {
set_mnt_shared(mnt);
return;
}
do_make_slave(mnt);
if (type != MS_SLAVE) {
list_del_init(&mnt->mnt_slave);
mnt->mnt_master = NULL;
if (type == MS_UNBINDABLE)
mnt->mnt.mnt_flags |= MNT_UNBINDABLE;
else
mnt->mnt.mnt_flags &= ~MNT_UNBINDABLE;
}
}
/*
* 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 mount *propagation_next(struct mount *m,
struct mount *origin)
{
/* are there any slaves of this mount? */
if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
return first_slave(m);
while (1) {
struct mount *master = m->mnt_master;
if (master == origin->mnt_master) {
struct mount *next = next_peer(m);
return (next == origin) ? NULL : next;
} else if (m->mnt_slave.next != &master->mnt_slave_list)
return next_slave(m);
/* back at master */
m = master;
}
}
/*
* return the source mount to be used for cloning
*
* @dest the current destination mount
* @last_dest the last seen destination mount
* @last_src the last seen source mount
* @type return CL_SLAVE if the new mount has to be
* cloned as a slave.
*/
static struct mount *get_source(struct mount *dest,
struct mount *last_dest,
struct mount *last_src,
int *type)
{
struct mount *p_last_src = NULL;
struct mount *p_last_dest = NULL;
while (last_dest != dest->mnt_master) {
p_last_dest = last_dest;
p_last_src = last_src;
last_dest = last_dest->mnt_master;
last_src = last_src->mnt_master;
}
if (p_last_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;
}
}
/* 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;
}
/*
* mount 'source_mnt' under the destination 'dest_mnt' at
* dentry 'dest_dentry'. And propagate that mount to
* all the peer and slave mounts of 'dest_mnt'.
* Link all the new mounts into a propagation tree headed at
* source_mnt. Also link all the new mounts using ->mnt_list
* headed at source_mnt's ->mnt_list
*
* @dest_mnt: destination mount.
* @dest_dentry: destination dentry.
* @source_mnt: source mount.
* @tree_list : list of heads of trees to be attached.
*/
int propagate_mnt(struct mount *dest_mnt, struct dentry *dest_dentry,
struct mount *source_mnt, struct list_head *tree_list)
{
struct mount *m, *child;
int ret = 0;
struct mount *prev_dest_mnt = dest_mnt;
struct mount *prev_src_mnt = source_mnt;
LIST_HEAD(tmp_list);
LIST_HEAD(umount_list);
for (m = propagation_next(dest_mnt, dest_mnt); m;
m = propagation_next(m, dest_mnt)) {
int type;
struct mount *source;
if (IS_MNT_NEW(m))
continue;
source = get_source(m, prev_dest_mnt, prev_src_mnt, &type);
if (!(child = copy_tree(source, source->mnt.mnt_root, type))) {
ret = -ENOMEM;
list_splice(tree_list, tmp_list.prev);
goto out;
}
if (is_subdir(dest_dentry, m->mnt.mnt_root)) {
mnt_set_mountpoint(m, dest_dentry, child);
list_add_tail(&child->mnt_hash, tree_list);
} else {
/*
* This can happen if the parent mount was bind mounted
* on some subdirectory of a shared/slave mount.
*/
list_add_tail(&child->mnt_hash, &tmp_list);
}
prev_dest_mnt = m;
prev_src_mnt = child;
}
out:
br_write_lock(&vfsmount_lock);
while (!list_empty(&tmp_list)) {
child = list_first_entry(&tmp_list, struct mount, mnt_hash);
umount_tree(child, 0, &umount_list);
}
br_write_unlock(&vfsmount_lock);
release_mounts(&umount_list);
return ret;
}
/*
* return true if the refcount is greater than count
*/
static inline int do_refcount_check(struct mount *mnt, int count)
{
int mycount = mnt_get_count(mnt) - mnt->mnt_ghosts;
return (mycount > count);
}
/*
* check if the mount 'mnt' can be unmounted successfully.
* @mnt: the mount to be checked for unmount
* NOTE: unmounting 'mnt' would naturally propagate to all
* other mounts its parent propagates to.
* Check if any of these mounts that **do not have submounts**
* have more references than 'refcnt'. If so return busy.
*
* vfsmount lock must be held for write
*/
int propagate_mount_busy(struct mount *mnt, int refcnt)
{
struct mount *m, *child;
struct mount *parent = mnt->mnt_parent;
int ret = 0;
if (mnt == parent)
return do_refcount_check(mnt, refcnt);
/*
* quickly check if the current mount can be unmounted.
* If not, we don't have to go checking for all other
* mounts
*/
if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt))
return 1;
for (m = propagation_next(parent, parent); m;
m = propagation_next(m, parent)) {
child = __lookup_mnt(&m->mnt, mnt->mnt_mountpoint, 0);
if (child && list_empty(&child->mnt_mounts) &&
(ret = do_refcount_check(child, 1)))
break;
}
return ret;
}
/*
* NOTE: unmounting 'mnt' naturally propagates to all other mounts its
* parent propagates to.
*/
static void __propagate_umount(struct mount *mnt)
{
struct mount *parent = mnt->mnt_parent;
struct mount *m;
BUG_ON(parent == mnt);
for (m = propagation_next(parent, parent); m;
m = propagation_next(m, parent)) {
struct mount *child = __lookup_mnt(&m->mnt,
mnt->mnt_mountpoint, 0);
/*
* umount the child only if the child has no
* other children
*/
if (child && list_empty(&child->mnt_mounts))
list_move_tail(&child->mnt_hash, &mnt->mnt_hash);
}
}
/*
* collect all mounts that receive propagation from the mount in @list,
* and return these additional mounts in the same list.
* @list: the list of mounts to be unmounted.
*
* vfsmount lock must be held for write
*/
int propagate_umount(struct list_head *list)
{
struct mount *mnt;
list_for_each_entry(mnt, list, mnt_hash)
__propagate_umount(mnt);
return 0;
}