On 8/4/2023 4:46 AM, Yu Zhao wrote: > On Wed, Aug 2, 2023 at 6:56 AM Yin, Fengwei <fengwei.yin@xxxxxxxxx> wrote: >> >> >> >> On 8/2/2023 8:49 PM, Ryan Roberts wrote: >>> On 02/08/2023 13:42, Yin, Fengwei wrote: >>>> >>>> >>>> On 8/2/2023 8:40 PM, Ryan Roberts wrote: >>>>> On 02/08/2023 13:35, Yin, Fengwei wrote: >>>>>> >>>>>> >>>>>> On 8/2/2023 6:27 PM, Ryan Roberts wrote: >>>>>>> On 28/07/2023 17:13, Yin Fengwei wrote: >>>>>>>> In madvise_cold_or_pageout_pte_range() and madvise_free_pte_range(), >>>>>>>> folio_mapcount() is used to check whether the folio is shared. But it's >>>>>>>> not correct as folio_mapcount() returns total mapcount of large folio. >>>>>>>> >>>>>>>> Use folio_estimated_sharers() here as the estimated number is enough. >>>>>>>> >>>>>>>> Yin Fengwei (2): >>>>>>>> madvise: don't use mapcount() against large folio for sharing check >>>>>>>> madvise: don't use mapcount() against large folio for sharing check >>>>>>>> >>>>>>>> mm/huge_memory.c | 2 +- >>>>>>>> mm/madvise.c | 6 +++--- >>>>>>>> 2 files changed, 4 insertions(+), 4 deletions(-) >>>>>>>> >>>>>>> >>>>>>> As a set of fixes, I agree this is definitely an improvement, so: >>>>>>> >>>>>>> Reviewed-By: Ryan Roberts >>>>>> Thanks. >>>>>> >>>>>>> >>>>>>> >>>>>>> But I have a couple of comments around further improvements; >>>>>>> >>>>>>> Once we have the scheme that David is working on to be able to provide precise >>>>>>> exclusive vs shared info, we will probably want to move to that. Although that >>>>>>> scheme will need access to the mm_struct of a process known to be mapping the >>>>>>> folio. We have that info, but its not passed to folio_estimated_sharers() so we >>>>>>> can't just reimplement folio_estimated_sharers() - we will need to rework these >>>>>>> call sites again. >>>>>> Yes. This could be extra work. Maybe should delay till David's work is done. >>>>> >>>>> What you have is definitely an improvement over what was there before. And is >>>>> probably the best we can do without David's scheme. So I wouldn't delay this. >>>>> Just pointing out that we will be able to make it even better later on (if >>>>> David's stuff goes in). >>>> Yes. I agree that we should wait for David's work ready and do fix based on that. >>> >>> I was suggesting the opposite - not waiting. Then we can do separate improvement >>> later. >> Let's wait for David's work ready. > > Waiting is fine as long as we don't miss the next merge window -- we > don't want these two bugs to get into another release. Also I think we > should cc stable, since as David mentioned, they have been causing > selftest failures. Stable was CCed. Andrew asked about the user-visible impact and I replied: https://lore.kernel.org/linux-mm/24e7429c-14ed-d953-e652-eac178de76e3@xxxxxxxxx/ I was not aware that selftest is impact by the issue. And waiting for whether these patches are necessary for stable. But I don't want to promote this kind of change in other place as we will move to David's solution. Regards Yin, Fengwei
