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SubjectRe: [PATCH v2] ovl: provide real_file() and overlayfs get_unmapped_area()
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On 5/28/20 1:37 AM, kbuild test robot wrote:
> Hi Mike,
>
> I love your patch! Yet something to improve:
>
> [auto build test ERROR on miklos-vfs/overlayfs-next]
> [also build test ERROR on linus/master v5.7-rc7]
> [cannot apply to linux/master next-20200526]
> [if your patch is applied to the wrong git tree, please drop us a note to help
> improve the system. BTW, we also suggest to use '--base' option to specify the
> base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
>
> url: https://github.com/0day-ci/linux/commits/Mike-Kravetz/ovl-provide-real_file-and-overlayfs-get_unmapped_area/20200528-080533
> base: https://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs.git overlayfs-next
> config: h8300-randconfig-r036-20200528 (attached as .config)
> compiler: h8300-linux-gcc (GCC) 9.3.0
> reproduce (this is a W=1 build):
> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # save the attached .config to linux build tree
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=h8300
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kbuild test robot <lkp@intel.com>
>
> All error/warnings (new ones prefixed by >>, old ones prefixed by <<):
>
> fs/overlayfs/file.c: In function 'ovl_get_unmapped_area':
>>> fs/overlayfs/file.c:768:14: error: 'struct mm_struct' has no member named 'get_unmapped_area'
> 768 | current->mm->get_unmapped_area)(realfile,
> | ^~
>>> fs/overlayfs/file.c:770:1: warning: control reaches end of non-void function [-Wreturn-type]
> 770 | }
> | ^
>
> vim +768 fs/overlayfs/file.c
>
> 760
> 761 static unsigned long ovl_get_unmapped_area(struct file *file,
> 762 unsigned long uaddr, unsigned long len,
> 763 unsigned long pgoff, unsigned long flags)
> 764 {
> 765 struct file *realfile = real_file(file);
> 766
> 767 return (realfile->f_op->get_unmapped_area ?:
> > 768 current->mm->get_unmapped_area)(realfile,
> 769 uaddr, len, pgoff, flags);
> > 770 }
> 771
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
>

Well yuck! get_unmapped_area is not part of mm_struct if !CONFIG_MMU.

Miklos, would adding '#ifdef CONFIG_MMU' around the overlayfs code be too
ugly for you? Another option is to use real_file() in the mmap code as
done in [1].

Sorry for all the questions. However, I want to make sure you are happy
with any overlayfs changes.

[1] https://lore.kernel.org/linux-mm/04a00e3b-539c-236f-e43b-0024ef94b7cb@oracle.com/
--
Mike Kravetz

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