Re: [v3 PATCH 2/5] mm: filemap: check if THP has hwpoisoned subpage for PMD page fault

[Naresh Kamboju]

Hi Yang,

On Fri, 1 Oct 2021 at 03:23, Yang Shi <shy828301@xxxxxxxxx> wrote:
>
> When handling shmem page fault the THP with corrupted subpage could be PMD
> mapped if certain conditions are satisfied.  But kernel is supposed to
> send SIGBUS when trying to map hwpoisoned page.
>
> There are two paths which may do PMD map: fault around and regular fault.
>
> Before commit f9ce0be71d1f ("mm: Cleanup faultaround and finish_fault() codepaths")
> the thing was even worse in fault around path.  The THP could be PMD mapped as
> long as the VMA fits regardless what subpage is accessed and corrupted.  After
> this commit as long as head page is not corrupted the THP could be PMD mapped.
>
> In the regular fault path the THP could be PMD mapped as long as the corrupted
> page is not accessed and the VMA fits.
>
> This loophole could be fixed by iterating every subpage to check if any
> of them is hwpoisoned or not, but it is somewhat costly in page fault path.
>
> So introduce a new page flag called HasHWPoisoned on the first tail page.  It
> indicates the THP has hwpoisoned subpage(s).  It is set if any subpage of THP
> is found hwpoisoned by memory failure and cleared when the THP is freed or
> split.
>
> Fixes: 800d8c63b2e9 ("shmem: add huge pages support")
> Cc: <stable@xxxxxxxxxxxxxxx>
> Suggested-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Signed-off-by: Yang Shi <shy828301@xxxxxxxxx>
> ---
>  include/linux/page-flags.h | 19 +++++++++++++++++++
>  mm/filemap.c               | 12 ++++++------
>  mm/huge_memory.c           |  2 ++
>  mm/memory-failure.c        |  6 +++++-
>  mm/memory.c                |  9 +++++++++
>  mm/page_alloc.c            |  4 +++-
>  6 files changed, 44 insertions(+), 8 deletions(-)

When CONFIG_MEMORY_FAILURE not set
we get these build failures.

Regression found on x86_64 and i386 gcc-11 builds
Following build warnings / errors reported on Linux mainline master.

metadata:
    git_describe: v5.15-559-g19901165d90f
    git_repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
    git_short_log: 19901165d90f (\"Merge tag
'for-5.16/inode-sync-2021-10-29' of git://git.kernel.dk/linux-block\")
    target_arch: x86_64
    toolchain: gcc-11


In file included from include/linux/mmzone.h:22,
                 from include/linux/gfp.h:6,
                 from include/linux/slab.h:15,
                 from include/linux/crypto.h:20,
                 from arch/x86/kernel/asm-offsets.c:9:
include/linux/page-flags.h:806:29: error: macro "PAGEFLAG_FALSE"
requires 2 arguments, but only 1 given
  806 | PAGEFLAG_FALSE(HasHWPoisoned)
      |                             ^
include/linux/page-flags.h:411: note: macro "PAGEFLAG_FALSE" defined here
  411 | #define PAGEFLAG_FALSE(uname, lname) TESTPAGEFLAG_FALSE(uname,
lname)   \
      |
include/linux/page-flags.h:807:39: error: macro "TESTSCFLAG_FALSE"
requires 2 arguments, but only 1 given
  807 |         TESTSCFLAG_FALSE(HasHWPoisoned)
      |                                       ^
include/linux/page-flags.h:414: note: macro "TESTSCFLAG_FALSE" defined here
  414 | #define TESTSCFLAG_FALSE(uname, lname)
         \
      |
include/linux/page-flags.h:806:1: error: unknown type name 'PAGEFLAG_FALSE'
  806 | PAGEFLAG_FALSE(HasHWPoisoned)
      | ^~~~~~~~~~~~~~
include/linux/page-flags.h:807:25: error: expected ';' before 'static'
  807 |         TESTSCFLAG_FALSE(HasHWPoisoned)
      |                         ^
      |                         ;
......
  815 | static inline bool is_page_hwpoison(struct page *page)
      | ~~~~~~
make[2]: *** [scripts/Makefile.build:121: arch/x86/kernel/asm-offsets.s] Error 1

Reported-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>

build link:
-----------
https://builds.tuxbuild.com/20KPBpXK6K0bKSIKAIKfwlBq7O4/build.log

build config:
-------------
https://builds.tuxbuild.com/20KPBpXK6K0bKSIKAIKfwlBq7O4/config

# To install tuxmake on your system globally
# sudo pip3 install -U tuxmake

tuxmake --runtime podman --target-arch x86_64 --toolchain gcc-11
--kconfig defconfig --kconfig-add
https://builds.tuxbuild.com/20KPBpXK6K0bKSIKAIKfwlBq7O4/config

link:
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