Re: [PATCH] NFSv4: fix getacl ERANGE for some ACL buffer sizes

["J. Bruce Fields" <bfields@fieldses.org>]

On Mon, Dec 14, 2015 at 06:27:20PM -0500, Trond Myklebust wrote:
> On Mon, Dec 14, 2015 at 5:21 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
> > From: Weston Andros Adamson <dros@netapp.com>
> >
> > Fix a bug where getxattr returns ERANGE when the attr buffer
> > length is close enough to the nearest PAGE_SIZE multiple that adding
> > the extra bytes leaves too little room for the ACL buffer.
> >
> > Besides storing the ACL buffer, the getacl decoder uses the inline
> > pages for the attr bitmap and buffer length. __nfs4_get_acl_uncached
> > must allocate enough page space for all of the data to be decoded.
> >
> > This patch uses xdr_partial_copy_from_skb to allocate any needed
> > pages past the first one. This allows the client to always cache the acl
> > on the first getacl call and not just if it fits in one page.
> >
> > Signed-off-by: Weston Andros Adamson <dros@netapp.com>
> > Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> 
> The thread ends with:
> 
> "Indeed, buf->page_len is still set to the maximum number of bytes in
> the pages array (set by xdr_inline_pages to tell xdr layer the max
> allocation size), and not the number of bytes that are actually
> present.
> 
> Working on a fix.
> 
> -dros"

Dros, do you have a reliable reproducer for the BUG you were seeing?
I'm not having any luck.

--b.