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bh=qzK4ogixuaREht4MpkiqqhFPvzGg6ALQmBRRBO9bEhw=; b=Kwq3nV2qk0xO0Ne6RRdDvmjDTFVsboE4GBexKhuNhsq/wY7Hhcv3/R9zPmTfWmu/lbSuhq cjRmxyXHS+tgTEqhw/VtBlPT8HB9vH52VyeDiFeQYp61OdPifp4yHvwP9UotX8b7jnKA+W CwMgDI7sHk268elveK5I/MY0qKqPlf0= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-5-bQTcdzQuNdGs3XWMcEGz2w-1; Tue, 11 Apr 2023 10:15:42 -0400 X-MC-Unique: bQTcdzQuNdGs3XWMcEGz2w-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6FBF686A96C; Tue, 11 Apr 2023 14:15:32 +0000 (UTC) Received: from t480s.redhat.com (unknown [10.39.194.95]) by smtp.corp.redhat.com (Postfix) with ESMTP id DB346400F284; Tue, 11 Apr 2023 14:15:30 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, sparclinux@vger.kernel.org, David Hildenbrand Subject: [PATCH] mm/huge_memory: conditionally call maybe_mkwrite() and drop pte_wrprotect() in __split_huge_pmd_locked() Date: Tue, 11 Apr 2023 16:15:22 +0200 Message-Id: <20230411141529.428991-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 5ABA980036 X-Stat-Signature: be69kakybf8eracjibgp9ydu88xm97mm X-HE-Tag: 1681222548-984910 X-HE-Meta: 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 8d59ymuX 55b1q/c0bhfPmLGT30T3axZqgDda8LUs2OUI554+FjmmpZkPsCJozjonlj7tABg1NsWLdYRwu01Bb0CosyZF5faDUyu1bSbzfvof56EEWza8BcImK8ah9sjvtUpcDecx5GBNDt+B/Pj92doBSnSbr5tvq4Gvsb7JdWngl9ufTEdHhYc/2YdzT0Sthl90VCir+nYYOHMVSnvIlIY9POTutKqaqcGSiVxyY1KSdKsFWHGb1py0= 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: No need to call maybe_mkwrite() to then wrprotect if the source PMD was not writable. It's worth nothing that this now allows for PTEs to be writable even if the source PMD was not writable: if vma->vm_page_prot includes write permissions. As documented in commit 931298e103c2 ("mm/userfaultfd: rely on vma->vm_page_prot in uffd_wp_range()"), any mechanism that intends to have pages wrprotected (COW, writenotify, mprotect, uffd-wp, softdirty, ...) has to properly adjust vma->vm_page_prot upfront, to not include write permissions. If vma->vm_page_prot includes write permissions, the PTE/PMD can be writable as default. This now mimics the handling in mm/migrate.c:remove_migration_pte() and in mm/huge_memory.c:remove_migration_pmd(), which has been in place for a long time (except that 96a9c287e25d ("mm/migrate: fix wrongly apply write bit after mkdirty on sparc64") temporarily changed it). Signed-off-by: David Hildenbrand --- mm/huge_memory.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 6f3af65435c8..8332e16ac97b 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2235,11 +2235,10 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, entry = pte_swp_mkuffd_wp(entry); } else { entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot)); - entry = maybe_mkwrite(entry, vma); + if (write) + entry = maybe_mkwrite(entry, vma); if (anon_exclusive) SetPageAnonExclusive(page + i); - if (!write) - entry = pte_wrprotect(entry); if (!young) entry = pte_mkold(entry); /* NOTE: this may set soft-dirty too on some archs */