On Fri, Oct 01, 2010 at 11:12:48AM +0200, Szeredi Miklos wrote: > On Fri, Oct 1, 2010 at 3:58 AM, Ram Pai <linuxram@xxxxxxxxxx> wrote: > > > > > > @@ -1212,11 +1216,12 @@ struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, > > > > > > ? ? ? ? struct path path; > > > > > > > > > > > > ? ? ? ? if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt)) > > > > > > - ? ? ? ? ? ? ? return NULL; > > > > > > + ? ? ? ? ? ? ? return ERR_PTR(-EINVAL); > > > > > > > > Ram, do you remember how this worked? > > > > > > Oops. That should be a OR condition. there is one other check in that > > > function that should also be a OR condition. > > > > I may be wrong here. Can't exactly recollect what CL_COPY_ALL flag means. Al Viro > > might remember? ?If CL_COPY_ALL means, to clone everything irrespective of any other > > flags, then the above code seems right. > > CL_COPY_ALL means clone the mount despite MNT_UNBINDABLE. It is used > for cloning the whole namespace and for collect_mounts(), both of > which ignore MNT_UNBINDABLE. > > Of the two remaining callers of copy_tree() do_loopback already checks > MNT_UNBINDABLE on the root of the tree to be copied. I reviewed and tested and agree. But I don't think this change should go into stable. It doesn't fix any existing bug and I don't like perturbing the code in stable for a code cleanup. > So that leaves the one in pnode.c. That one will be called when > attaching a new mount or mount tree. If the root of that tree is > unbindable then the propagation will fail with -ENOMEM which is wrong, > it should simply skip the whole tree and not try to propagate. Calls Not try to propagate - and return an error? Or succeed and ignore? > which result in propagation are do_loopback, do_move_mount and > do_add_mount. Of this do_loopback and do_move_mount already check for > MNT_UNBINDABLE, do_add_mount doesn't check, but should probably just > mask out MNT_UNBINDABLE. Hm, if we stop trusting callers of do_add_mount(), we should probably do a lot more than just mask this out. Interestingly, most out-of-VFS callers just seem to add MNT_SHRINKABLE, maybe we should export do_add_shrinkable() instead or something like that? > So in the end that check in copy_tree() should never actually trigger > and can be turned into a WARN_ON WARN_ON() makes sense. > Additionally the propagation code should perhaps be more defensive and > skip MNT_UNBINDABLE source mounts. Maybe WARN_ON() here too? I'm not going to get around to revamping this part of mount propagation until after I finish union mount copyup rewrite, anyone else up for doing it sooner? -VAL -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
