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[70.27.3.10]) by smtp.gmail.com with ESMTPSA id o9-20020a056e0214c900b002de990656f5sm2248531ilk.32.2022.08.10.08.13.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Aug 2022 08:13:40 -0700 (PDT) Date: Wed, 10 Aug 2022 11:13:39 -0400 From: Peter Xu To: "Huang, Ying" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Minchan Kim , David Hildenbrand , Nadav Amit , Andrew Morton , Hugh Dickins , Vlastimil Babka , Andrea Arcangeli , Andi Kleen , "Kirill A . Shutemov" Subject: Re: [PATCH v3 4/7] mm/thp: Carry over dirty bit when thp splits on pmd Message-ID: References: <20220809220100.20033-1-peterx@redhat.com> <20220809220100.20033-5-peterx@redhat.com> <877d3gfwf2.fsf@yhuang6-desk2.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <877d3gfwf2.fsf@yhuang6-desk2.ccr.corp.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 10, 2022 at 02:24:33PM +0800, Huang, Ying wrote: > Peter Xu writes: > > > Carry over the dirty bit from pmd to pte when a huge pmd splits. It > > shouldn't be a correctness issue since when pmd_dirty() we'll have the page > > marked dirty anyway, however having dirty bit carried over helps the next > > initial writes of split ptes on some archs like x86. > > > > Signed-off-by: Peter Xu > > --- > > mm/huge_memory.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > index 0611b2fd145a..e8e78d1bac5f 100644 > > --- a/mm/huge_memory.c > > +++ b/mm/huge_memory.c > > @@ -2005,7 +2005,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > > pgtable_t pgtable; > > pmd_t old_pmd, _pmd; > > bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false; > > - bool anon_exclusive = false; > > + bool anon_exclusive = false, dirty = false; > > unsigned long addr; > > int i; > > > > @@ -2098,6 +2098,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > > SetPageDirty(page); > > write = pmd_write(old_pmd); > > young = pmd_young(old_pmd); > > + dirty = pmd_dirty(old_pmd); > > Nitpick: This can be put under > > if (pmd_dirty(old_pmd)) > SetPageDirty(page); > > Not a big deal. > > Reviewed-by: "Huang, Ying" Yeah will do, thanks. -- Peter Xu