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. Ok. That reminds me when the above piece of code in copy_tree() is triggered. It triggered when a mount tree with a unbindable mount at its head is moved on a shared mount with atleast one peer. something like this should trigger the code. # create a unbindable mount mkdir -p /mnt2/m1 mount --bind /mnt2/m1 /mnt2/m1 mount --make-unbindable /mnt2/m1 #create a shared mount with one peer. mkdir -p /mnt2/s1 mkdir -p /mnt2/s2 mount --bind /mnt2/s1 /mnt2/s1 mount --make-shared /mnt2/s1 mount --bind /mnt2/s1 /mnt2/s2 #move the unbindable mount to one of the shared peer mkdir -p /mnt2/s1/movemount mount --move /mnt2/m1 /mnt2/s1/movemount the last step will fail and that is because of the above check in copy_tree() > > Of the two remaining callers of copy_tree() do_loopback already checks > MNT_UNBINDABLE on the root of the tree to be copied. > > 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. Yes. the propagation_mnt() should fail if it is unable to create clones of the source mount due to any reason. However -ENOMEM may not be the right return code. > Calls > 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. > > So in the end that check in copy_tree() should never actually trigger > and can be turned into a WARN_ON You can do that. But then we have to catch for the cases where a unbindable mount is moved on a shared mounts. I suppose we can put in a check in do_move_mount(). > > Additionally the propagation code should perhaps be more defensive and > skip MNT_UNBINDABLE source mounts. No. If we do that, I am afraid, we will end up with inconsistent peer-mount trees which will not resemble each other. RP > > Thanks, > Miklos -- 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
