[RFC v14-rc2][PATCH 16/29] A new file type (CR_FD_OBJREF) for a file descriptor already setup

[Oren Laadan]

Dan Smith wrote:
> OL> @@ -86,46 +132,44 @@ static int cr_read_file(struct cr_ctx *ctx, int objref)
> OL>  		goto out;
> 
> OL>  	ret = -EINVAL;
> OL> +	if (hh->fd_objref < 0)
> OL> +		goto out;
> 
> As far as I can tell, hh->fd_objref never gets set anywhere.  On my
> system, this causes restart to always fail because there is garbage in
> that field, thus triggering the above check.  If I remove this,
> restart completes successfully.  The following grep tells me that
> maybe this check isn't valid:
> 
>   % grep fd_objref checkpoint/*.c include/linux/checkpoint*.h
>   checkpoint/rstr_file.c: file = cr_obj_get_by_ref(ctx, hh->fd_objref, CR_OBJ_FILE);
>   checkpoint/rstr_file.c: file = cr_obj_add_file(ctx, fds[1-which], hh->fd_objref);
>   checkpoint/rstr_file.c:static int cr_read_fd_objref(struct cr_ctx *ctx, struct cr_hdr_file *hh)
>   checkpoint/rstr_file.c: file = cr_obj_get_by_ref(ctx, hh->fd_objref, CR_OBJ_FILE);
>   checkpoint/rstr_file.c: if (hh->fd_objref < 0)
>   checkpoint/rstr_file.c:	fd = cr_read_fd_objref(ctx, hh);
>   include/linux/checkpoint_hdr.h:	__s32 fd_objref;

hh->fd_objref is set, for pipes, in fs/pipe.c (outcome of the move to f_ops).
So the problem is that the field isn't explicitly zeroed otherwise. I'll fix
that for the next round. Meanwhile, you can add:

	hh->fd_objref = 0;

in cr_write_file() before the call to file->f_ops->checkpoint().

Thanks,

Oren.

> 
> I haven't looked into the surrounding bits yet, so maybe I'm missing
> something, but this seems to be causing a spurious failure on s390 at
> least.
> 
> I'm doing this on a clone of your repository's ckpt-v14-rc2 branch.
> Perhaps that repo is missing a patch?
>