Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Laurent Dufour <ldufour@linux.vnet.ibm.com>
To:     paulmck@linux.vnet.ibm.com, peterz@infradead.org,
        akpm@linux-foundation.org, kirill@shutemov.name,
        ak@linux.intel.com, mhocko@kernel.org, dave@stgolabs.net,
        jack@suse.cz, Matthew Wilcox <willy@infradead.org>,
        benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, hpa@zytor.com,
        Will Deacon <will.deacon@arm.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        kemi.wang@intel.com, sergey.senozhatsky.work@gmail.com,
        Daniel Jordan <daniel.m.jordan@oracle.com>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        haren@linux.vnet.ibm.com, khandual@linux.vnet.ibm.com,
        npiggin@gmail.com, bsingharora@gmail.com,
        Tim Chen <tim.c.chen@linux.intel.com>,
        linuxppc-dev@lists.ozlabs.org, x86@kernel.org
Subject: [PATCH v7 14/24] mm: Introduce __maybe_mkwrite()
Date:   Tue,  6 Feb 2018 17:50:00 +0100
In-Reply-To: <1517935810-31177-1-git-send-email-ldufour@linux.vnet.ibm.com>
References: <1517935810-31177-1-git-send-email-ldufour@linux.vnet.ibm.com>
Message-Id: <1517935810-31177-15-git-send-email-ldufour@linux.vnet.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

The current maybe_mkwrite() is getting passed the pointer to the vma
structure to fetch the vm_flags field.

When dealing with the speculative page fault handler, it will be better to
rely on the cached vm_flags value stored in the vm_fault structure.

This patch introduce a __maybe_mkwrite() service which can be called by
passing the value of the vm_flags field.

There is no change functional changes expected for the other callers of
maybe_mkwrite().

Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
---
 include/linux/mm.h | 9 +++++++--
 mm/memory.c        | 6 +++---
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index c034f478b73d..4976ea1a8c90 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -685,13 +685,18 @@ void free_compound_page(struct page *page);
  * pte_mkwrite.  But get_user_pages can cause write faults for mappings
  * that do not have writing enabled, when used by access_process_vm.
  */
-static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
+static inline pte_t __maybe_mkwrite(pte_t pte, unsigned long vma_flags)
 {
-	if (likely(vma->vm_flags & VM_WRITE))
+	if (likely(vma_flags & VM_WRITE))
 		pte = pte_mkwrite(pte);
 	return pte;
 }
 
+static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
+{
+	return __maybe_mkwrite(pte, vma->vm_flags);
+}
+
 int alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
 		struct page *page);
 int finish_fault(struct vm_fault *vmf);
diff --git a/mm/memory.c b/mm/memory.c
index 2e4c5755cbc1..eb84429be9ea 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2452,7 +2452,7 @@ static inline void wp_page_reuse(struct vm_fault *vmf)
 
 	flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
 	entry = pte_mkyoung(vmf->orig_pte);
-	entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+	entry = __maybe_mkwrite(pte_mkdirty(entry), vmf->vma_flags);
 	if (ptep_set_access_flags(vma, vmf->address, vmf->pte, entry, 1))
 		update_mmu_cache(vma, vmf->address, vmf->pte);
 	pte_unmap_unlock(vmf->pte, vmf->ptl);
@@ -2543,8 +2543,8 @@ static int wp_page_copy(struct vm_fault *vmf)
 			inc_mm_counter_fast(mm, MM_ANONPAGES);
 		}
 		flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
-		entry = mk_pte(new_page, vma->vm_page_prot);
-		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+		entry = mk_pte(new_page, vmf->vma_page_prot);
+		entry = __maybe_mkwrite(pte_mkdirty(entry), vmf->vma_flags);
 		/*
 		 * Clear the pte entry and flush it first, before updating the
 		 * pte with the new entry. This will avoid a race condition
-- 
2.7.4