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Miller" , Peter Xu , Hugh Dickins , Shuah Khan , Sam Ravnborg , Yu Zhao , Anshuman Khandual Subject: [PATCH v1 RESEND 6/6] mm/huge_memory: conditionally call maybe_mkwrite() and drop pte_wrprotect() in __split_huge_pmd_locked() Date: Tue, 11 Apr 2023 16:25:12 +0200 Message-Id: <20230411142512.438404-7-david@redhat.com> In-Reply-To: <20230411142512.438404-1-david@redhat.com> References: <20230411142512.438404-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 3A548C000E X-Stat-Signature: c831ezww6pmsjgtcjxaxzz84nbtwitkg X-HE-Tag: 1681223136-453165 X-HE-Meta: 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 3qJh0+2B zjNxvx/3sIy9tPd4MQPpqMunWrF2rI89W3q+xURmPHaobUTw3tvvFCa5H9qFVf3RRPM6OG1XhcLdIF1m2yUCxD58Dc0f/x6z+3Nu/fDG96FGuK7xZT43hvqSrjObsO1rEG6vuxqqjSaDLR8H5KHPt8lXowjusY6jY85rk8X9PeDeSAsL0g3x6NvtoyvcWMf8nZFEwIecJZFM4RVTNfPqV4iE9cav2IFxeVWZKv4/5o6finhQ= 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 */