Re: [PATCH v9 02/10] mm: Non-pmd-mappable, large folios for folio_add_new_anon_rmap()

[Jiri Olsa]

On Wed, Jan 24, 2024 at 12:02:53PM +0000, Ryan Roberts wrote:
> On 24/01/2024 11:19, Jiri Olsa wrote:
> > On Wed, Jan 24, 2024 at 12:15:52PM +0100, Sven Schnelle wrote:
> >> Ryan Roberts <ryan.roberts@xxxxxxx> writes:
> >>
> >>> On 14/01/2024 20:55, Jiri Olsa wrote:
> >>>> On Sun, Jan 14, 2024 at 06:33:56PM +0100, David Hildenbrand wrote:
> >>>>> On 13.01.24 23:42, Jiri Olsa wrote:
> >>>>>> On Thu, Dec 07, 2023 at 04:12:03PM +0000, Ryan Roberts wrote:
> >>>>>>> In preparation for supporting anonymous multi-size THP, improve
> >>>>>>> folio_add_new_anon_rmap() to allow a non-pmd-mappable, large folio to be
> >>>>>>> passed to it. In this case, all contained pages are accounted using the
> >>>>>>> order-0 folio (or base page) scheme.
> >>>>>>>
> >>>>>>> Reviewed-by: Yu Zhao <yuzhao@xxxxxxxxxx>
> >>>>>>> Reviewed-by: Yin Fengwei <fengwei.yin@xxxxxxxxx>
> >>>>>>> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
> >>>>>>> Reviewed-by: Barry Song <v-songbaohua@xxxxxxxx>
> >>>>>>> Tested-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> >>>>>>> Tested-by: John Hubbard <jhubbard@xxxxxxxxxx>
> >>>>>>> Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
> >>>>>>> ---
> >>>>>>>   mm/rmap.c | 28 ++++++++++++++++++++--------
> >>>>>>>   1 file changed, 20 insertions(+), 8 deletions(-)
> >>>>>>>
> >>>>>>> diff --git a/mm/rmap.c b/mm/rmap.c
> >>>>>>> index 2a1e45e6419f..846fc79f3ca9 100644
> >>>>>>> --- a/mm/rmap.c
> >>>>>>> +++ b/mm/rmap.c
> >>>>>>> @@ -1335,32 +1335,44 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma,
> >>>>>>>    * This means the inc-and-test can be bypassed.
> >>>>>>>    * The folio does not have to be locked.
> >>>>>>>    *
> >>>>>>> - * If the folio is large, it is accounted as a THP.  As the folio
> >>>>>>> + * If the folio is pmd-mappable, it is accounted as a THP.  As the folio
> >>>>>>>    * is new, it's assumed to be mapped exclusively by a single process.
> >>>>>>>    */
> >>>>>>>   void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
> >>>>>>>   		unsigned long address)
> >>>>>>>   {
> >>>>>>> -	int nr;
> >>>>>>> +	int nr = folio_nr_pages(folio);
> >>>>>>> -	VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
> >>>>>>> +	VM_BUG_ON_VMA(address < vma->vm_start ||
> >>>>>>> +			address + (nr << PAGE_SHIFT) > vma->vm_end, vma);
> >>>>>>
> >>>>>> hi,
> >>>>>> I'm hitting this bug (console output below) with adding uprobe
> >>>>>> on simple program like:
> >>>>>>
> >>>>>>    $ cat up.c
> >>>>>>    int main(void)
> >>>>>>    {
> >>>>>>       return 0;
> >>>>>>    }
> >>>>>>
> >>>>>>    # bpftrace -e 'uprobe:/home/jolsa/up:_start {}'
> >>>>>>
> >>>>>>    $ ./up
> >>>>>>
> >>>>>> it's on top of current linus tree master:
> >>>>>>    052d534373b7 Merge tag 'exfat-for-6.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/linkinjeon/exfat
> >>>>>>
> >>>>>> before this patch it seems to work, I can send my .config if needed
> >>>
> >>> Thanks for the bug report!
> >>
> >> I just hit the same bug in our CI, but can't find the fix in -next. Is
> >> this in the queue somewhere?
> > 
> > we hit it as well, but I can see the fix in linux-next/master
> > 
> >   4c137bc28064 uprobes: use pagesize-aligned virtual address when replacing pages
> 
> Yes that's the one. Just to confirm: you are still hitting the VM_BUG_ON despite
> having this change in your kernel? Could you please send over the full bug log?

ah sorry.. I meant the change fixes the problem for us, it just did not
yet propagate through the merge cycle into bpf trees.. but I can see it
in linux-next tree, so it's probably just matter of time

jirka