Re: [memcg:since-3.5 41/99] (.text+0xa0998): undefined reference to `get_kernel_page'

[Michal Hocko <mhocko@suse.cz>]

On Mon 20-08-12 22:29:19, Wu Fengguang wrote:
> On Mon, Aug 20, 2012 at 04:12:31PM +0200, Michal Hocko wrote:
> > On Mon 20-08-12 21:22:09, Wu Fengguang wrote:
> > > On Mon, Aug 20, 2012 at 02:39:50PM +0200, Michal Hocko wrote:
> > > > On Mon 20-08-12 10:06:30, Mel Gorman wrote:
> > > > > On Mon, Aug 20, 2012 at 07:59:24AM +0800, Fengguang Wu wrote:
> > > > > > Hi Mel,
> > > > > > 
> > > > > > FYI, kernel build failed on
> > > > > > 
> > > > > > tree:   git://github.com/mstsxfx/memcg-devel.git since-3.5
> > > > > > head:   a49301bd151e60fc22dc5b934358a9bb80bed7b3
> > > > > > commit: c4183d4ae946b7965f2657cf97da742c87fa9d96 [41/99] nfs: enable swap on NFS
> > > > > > config: m32r-m32104ut_defconfig (attached as .config)
> > > > > > 
> > > > > > All related error/warning messages:
> > > > > > 
> > > > > > fs/built-in.o: In function `nfs_file_direct_read':
> > > > > > (.text+0xa0998): undefined reference to `get_kernel_page'
> > > > > > fs/built-in.o: In function `nfs_file_direct_write':
> > > > > > (.text+0xa10b8): undefined reference to `get_kernel_page'
> > > > > > 
> > > > > 
> > > > > Michal, as this is the memcg tree and not akpm or linux-next could this
> > > > > build error be a merge problem in your tree?
> > > > 
> > > > Hmm, maybe my tree is missing some follow up fix but git diff sees
> > > > nothin relevant. Neverheless I have noticed that both CONFIG_SWAP and
> > > > CONFIG_NFS_SWAP are disabled. get_kernel_page is defined in mm/swap.c
> > > > but that one should be compiled in regardless the SWAP configuration.
> > > 
> > > I find that at _that_ commit, get_kernel_page() is defined in
> > > mm/memory.c which will only be compiled on CONFIG_MMU.
> > > 
> > > The get_kernel_page*() definitions are later moved to mm/swap.c by
> > > 
> > > commit 6503ced02700f5f561c8a2a66f5d93117fb230cd
> > > Author:     Mel Gorman <mgorman@suse.de>
> > > CommitDate: Thu Jul 26 11:25:53 2012 +0200
> > > 
> > >     mm-add-get_kernel_page-for-pinning-of-kernel-addresses-for-i-o-fix
> >  
> > But that means that it is not CONFIG_MMU dependent anymore, right?
> 
> Yes. It presents a problem for bisectability, however it seems only a
> problem in the since-3.5 branch: the patches sent to Linus are
> actually in good order. So it should be fine.

OK, I see so this is a bisectability test and the tip of the branch
compiles without any issues, right?

> Btw, is it meaningful for me to test the bisectability of all the
> memcg branches? If not, you may give me a list or pattern for me to
> take care.

Well, I do not think that this kind of test makes sense for the tree
because fixups are always done as a separate commits to prevent from
rebasing. Andrew always folds the fixups into the final patch which is
sent to Linus or who ever should push it further.

Thanks
-- 
Michal Hocko
SUSE Labs