Messages in this thread | | | From | Yu Zhao <> | Date | Fri, 21 Jul 2023 12:57:37 -0600 | Subject | Re: [RFC PATCH v2 1/4] madvise: not use mapcount() against large folio for sharing check |
| |
On Fri, Jul 21, 2023 at 3:41 AM Yin Fengwei <fengwei.yin@intel.com> wrote: > > The commit > 07e8c82b5eff ("madvise: convert madvise_cold_or_pageout_pte_range() to > use folios") replaced the page_mapcount() with folio_mapcount() to > check whether the folio is shared by other mapping. > > But it's not correct for large folio. folio_mapcount() returns the > total mapcount of large folio which is not suitable to detect whether > the folio is shared. > > Use folio_estimated_sharers() which returns a estimated number of > shares. That means it's not 100% correct. But it should be OK for > madvise case here. > > Signed-off-by: Yin Fengwei <fengwei.yin@intel.com>
Fixes: Cc: stable
> @@ -383,7 +383,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, > folio = pfn_folio(pmd_pfn(orig_pmd)); > > /* Do not interfere with other mappings of this folio */ > - if (folio_mapcount(folio) != 1) > + if (folio_estimated_sharers(folio) != 1)
Strictly speaking, this isn't a bug. But it may be ok to include it in the same patch.
> goto huge_unlock; > > if (pageout_anon_only_filter && !folio_test_anon(folio)) > @@ -459,7 +459,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, > if (folio_test_large(folio)) { > int err; > > - if (folio_mapcount(folio) != 1) > + if (folio_estimated_sharers(folio) != 1) > break; > if (pageout_anon_only_filter && !folio_test_anon(folio)) > break; > @@ -682,7 +682,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
What about madvise_free_huge_pmd()? Should it be changed as well so that it's consistent with the first change? Either change both or neither.
> if (folio_test_large(folio)) { > int err; > > - if (folio_mapcount(folio) != 1) > + if (folio_estimated_sharers(folio) != 1)
This is another bug fix and should be in a separate patch.
> break; > if (!folio_trylock(folio)) > break;
Please send two separate fixes, and then:
Reviewed-by: Yu Zhao <yuzhao@google.com>
| |