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[2003:cb:c708:de00:549e:e4e4:98df:ff72]) by smtp.gmail.com with ESMTPSA id d20-20020a05600c34d400b0038caf684679sm2800030wmq.0.2022.03.22.06.08.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 22 Mar 2022 06:08:14 -0700 (PDT) Message-ID: <019a2159-57d6-c330-53c5-38458b6b5ec9@redhat.com> Date: Tue, 22 Mar 2022 14:08:13 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.6.2 Subject: Re: [RFC 2/3] mm: export zap_page_range() Content-Language: en-US To: Xiaoguang Wang , linux-mm@kvack.org, target-devel@vger.kernel.org, linux-scsi@vger.kernel.org Cc: linux-block@vger.kernel.org, xuyu@linux.alibaba.com, bostroesser@gmail.com References: <20220318095531.15479-1-xiaoguang.wang@linux.alibaba.com> <20220318095531.15479-3-xiaoguang.wang@linux.alibaba.com> <37d6b269-dd9d-dbd1-74b1-4191cc3d4bf9@linux.alibaba.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <37d6b269-dd9d-dbd1-74b1-4191cc3d4bf9@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 22.03.22 14:02, Xiaoguang Wang wrote: > hi, > >> On 18.03.22 10:55, Xiaoguang Wang wrote: >>> Module target_core_user will use it to implement zero copy feature. >>> >>> Signed-off-by: Xiaoguang Wang >>> --- >>> mm/memory.c | 1 + >>> 1 file changed, 1 insertion(+) >>> >>> diff --git a/mm/memory.c b/mm/memory.c >>> index 1f745e4d11c2..9974d0406dad 100644 >>> --- a/mm/memory.c >>> +++ b/mm/memory.c >>> @@ -1664,6 +1664,7 @@ void zap_page_range(struct vm_area_struct *vma, unsigned long start, >>> mmu_notifier_invalidate_range_end(&range); >>> tlb_finish_mmu(&tlb); >>> } >>> +EXPORT_SYMBOL_GPL(zap_page_range); >>> >>> /** >>> * zap_page_range_single - remove user pages in a given range >> To which VMAs will you be applying zap_page_range? I assume only to some >> special ones where you previously vm_insert_page(s)_mkspecial'ed pages, >> not to some otherwise random VMAs, correct? > Yes, you're right :) I'd suggest exposing a dedicated function that performs sanity checks on the vma (VM_PFNMAP ?) and only zaps within a single VMA. Essentially zap_page_range_single(), excluding "struct zap_details *details" and including sanity checks. Reason is that we don't want anybody to blindly zap_page_range() within random VMAs from a kernel module. -- Thanks, David / dhildenb