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[184.144.111.238]) by smtp.gmail.com with ESMTPSA id b25sm1625854qka.123.2021.07.14.15.21.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Jul 2021 15:21:22 -0700 (PDT) From: Peter Xu To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Jason Gunthorpe , peterx@redhat.com, Matthew Wilcox , Andrew Morton , Axel Rasmussen , Nadav Amit , Jerome Glisse , Mike Rapoport , Miaohe Lin , Hugh Dickins , Alistair Popple , Andrea Arcangeli , Mike Kravetz , "Kirill A . Shutemov" , David Hildenbrand Subject: [PATCH v4 01/26] mm/shmem: Unconditionally set pte dirty in mfill_atomic_install_pte Date: Wed, 14 Jul 2021 18:20:52 -0400 Message-Id: <20210714222117.47648-2-peterx@redhat.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210714222117.47648-1-peterx@redhat.com> References: <20210714222117.47648-1-peterx@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="US-ASCII" Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=LSy3Mqf4; spf=none (imf29.hostedemail.com: domain of peterx@redhat.com has no SPF policy when checking 216.205.24.124) smtp.mailfrom=peterx@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Stat-Signature: s77b15gzx76omdwtbe5bdbfbw13sg8cu X-Rspamd-Queue-Id: 3A76F900024F X-Rspamd-Server: rspam01 X-HE-Tag: 1626301285-520925 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: It was conditionally done previously, as there's one shmem special case t= hat we use SetPageDirty() instead. However that's not necessary and it should b= e easier and cleaner to do it unconditionally in mfill_atomic_install_pte()= . The most recent discussion about this is here, where Hugh explained the h= istory of SetPageDirty() and why it's possible that it's not required at all: https://lore.kernel.org/lkml/alpine.LSU.2.11.2104121657050.1097@eggly.anv= ils/ Currently mfill_atomic_install_pte() has three callers: 1. shmem_mfill_atomic_pte 2. mcopy_atomic_pte 3. mcontinue_atomic_pte After the change: case (1) should have its SetPageDirty replaced by the d= irty bit on pte (so we unify them together, finally), case (2) should have no functional change at all as it has page_in_cache=3D=3Dfalse, case (3) may= add a dirty bit to the pte. However since case (3) is UFFDIO_CONTINUE for shme= m, it's merely 100% sure the page is dirty after all, so should not make a r= eal difference either. This should make it much easier to follow on which case will set dirty fo= r uffd, as we'll simply set it all now for all uffd related ioctls. Meanwh= ile, no special handling of SetPageDirty() if there's no need. Cc: Hugh Dickins Cc: Axel Rasmussen Cc: Andrea Arcangeli Signed-off-by: Peter Xu --- mm/shmem.c | 1 - mm/userfaultfd.c | 3 +-- 2 files changed, 1 insertion(+), 3 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index 70d9ce294bb4..dc9f95b5fb34 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2449,7 +2449,6 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm= , shmem_recalc_inode(inode); spin_unlock_irq(&info->lock); =20 - SetPageDirty(page); unlock_page(page); return 0; out_delete_from_cache: diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 0e2132834bc7..b30a3724c701 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -69,10 +69,9 @@ int mfill_atomic_install_pte(struct mm_struct *dst_mm,= pmd_t *dst_pmd, pgoff_t offset, max_off; =20 _dst_pte =3D mk_pte(page, dst_vma->vm_page_prot); + _dst_pte =3D pte_mkdirty(_dst_pte); if (page_in_cache && !vm_shared) writable =3D false; - if (writable || !page_in_cache) - _dst_pte =3D pte_mkdirty(_dst_pte); if (writable) { if (wp_copy) _dst_pte =3D pte_mkuffd_wp(_dst_pte); --=20 2.31.1