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vfs: introduce clone_private_mount()

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Overlayfs needs a private clone of the mount, so create a function for
this and export to modules.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
This commit is contained in:
Miklos Szeredi 2014-10-24 00:14:36 +02:00
parent bd5d08569c
commit c771d683a6
2 changed files with 30 additions and 0 deletions
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27
fs/namespace.c
View File

@ -1686,6 +1686,33 @@ void drop_collected_mounts(struct vfsmount *mnt)
namespace_unlock(); namespace_unlock();
} }
/**
* clone_private_mount - create a private clone of a path
*
* This creates a new vfsmount, which will be the clone of @path. The new will
* not be attached anywhere in the namespace and will be private (i.e. changes
* to the originating mount won't be propagated into this).
*
* Release with mntput().
*/
struct vfsmount *clone_private_mount(struct path *path)
{
struct mount *old_mnt = real_mount(path->mnt);
struct mount *new_mnt;
if (IS_MNT_UNBINDABLE(old_mnt))
return ERR_PTR(-EINVAL);
down_read(&namespace_sem);
new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE);
up_read(&namespace_sem);
if (IS_ERR(new_mnt))
return ERR_CAST(new_mnt);
return &new_mnt->mnt;
}
EXPORT_SYMBOL_GPL(clone_private_mount);
int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
struct vfsmount *root) struct vfsmount *root)
{ {

3
include/linux/mount.h
View File

@ -81,6 +81,9 @@ extern struct vfsmount *mntget(struct vfsmount *mnt);
extern struct vfsmount *mnt_clone_internal(struct path *path); extern struct vfsmount *mnt_clone_internal(struct path *path);
extern int __mnt_is_readonly(struct vfsmount *mnt); extern int __mnt_is_readonly(struct vfsmount *mnt);
struct path;
extern struct vfsmount *clone_private_mount(struct path *path);
struct file_system_type; struct file_system_type;
extern struct vfsmount *vfs_kern_mount(struct file_system_type *type, extern struct vfsmount *vfs_kern_mount(struct file_system_type *type,
int flags, const char *name, int flags, const char *name,