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vfs: new internal helper: mnt_has_parent(mnt)

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vfsmounts have ->mnt_parent pointing either to a different vfsmount
or to itself; it's never NULL and termination condition in loops
traversing the tree towards root is mnt == mnt->mnt_parent.  At least
one place (see the next patch) is confused about what's going on;
let's add an explicit helper checking it right way and use it in
all places where we need it.  Not that there had been too many,
but...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2011-11-23 19:26:23 -05:00
parent aa9c0e07bb
commit b2dba1af3c
5 changed files with 18 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
fs/namespace.c
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@@ -1182,7 +1182,7 @@ void release_mounts(struct list_head *head)
while (!list_empty(head)) {
mnt = list_first_entry(head, struct vfsmount, mnt_hash);
list_del_init(&mnt->mnt_hash);
if (mnt->mnt_parent != mnt) {
if (mnt_has_parent(mnt)) {
struct dentry *dentry;
struct vfsmount *m;
@@ -1222,7 +1222,7 @@ void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill)
p->mnt_ns = NULL;
__mnt_make_shortterm(p);
list_del_init(&p->mnt_child);
if (p->mnt_parent != p) {
if (mnt_has_parent(p)) {
p->mnt_parent->mnt_ghosts++;
dentry_reset_mounted(p->mnt_parent, p->mnt_mountpoint);
}
@@ -1867,7 +1867,7 @@ static int do_move_mount(struct path *path, char *old_name)
if (old_path.dentry != old_path.mnt->mnt_root)
goto out1;
if (old_path.mnt == old_path.mnt->mnt_parent)
if (!mnt_has_parent(old_path.mnt))
goto out1;
if (S_ISDIR(path->dentry->d_inode->i_mode) !=
@@ -1887,7 +1887,7 @@ static int do_move_mount(struct path *path, char *old_name)
tree_contains_unbindable(old_path.mnt))
goto out1;
err = -ELOOP;
for (p = path->mnt; p->mnt_parent != p; p = p->mnt_parent)
for (p = path->mnt; mnt_has_parent(p); p = p->mnt_parent)
if (p == old_path.mnt)
goto out1;
@@ -2604,17 +2604,17 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
error = -EINVAL;
if (root.mnt->mnt_root != root.dentry)
goto out4; /* not a mountpoint */
if (root.mnt->mnt_parent == root.mnt)
if (!mnt_has_parent(root.mnt))
goto out4; /* not attached */
if (new.mnt->mnt_root != new.dentry)
goto out4; /* not a mountpoint */
if (new.mnt->mnt_parent == new.mnt)
if (!mnt_has_parent(new.mnt))
goto out4; /* not attached */
/* make sure we can reach put_old from new_root */
tmp = old.mnt;
if (tmp != new.mnt) {
for (;;) {
if (tmp->mnt_parent == tmp)
if (!mnt_has_parent(tmp))
goto out4; /* already mounted on put_old */
if (tmp->mnt_parent == new.mnt)
break;