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Gokhale" , Linus Torvalds , Yang Shi , Marty Mcfadden , Kirill Shutemov , Jann Horn , Jan Kara , Kirill Tkhai , Andrea Arcangeli , Christoph Hellwig , Andrew Morton Subject: Re: [PATCH 1/4] mm: Trial do_wp_page() simplification Message-ID: <20200915150349.GA22415@redhat.com> References: <20200821234958.7896-1-peterx@redhat.com> <20200821234958.7896-2-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200821234958.7896-2-peterx@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Rspamd-Queue-Id: 6F4EA180865A9 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 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: On 08/21, Peter Xu wrote: > > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -2927,50 +2927,25 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) > * not dirty accountable. > */ > if (PageAnon(vmf->page)) { > - int total_map_swapcount; > - if (PageKsm(vmf->page) && (PageSwapCache(vmf->page) || > - page_count(vmf->page) != 1)) > + struct page *page = vmf->page; > + > + /* PageKsm() doesn't necessarily raise the page refcount */ > + if (PageKsm(page) || page_count(page) != 1) > + goto copy; > + if (!trylock_page(page)) > + goto copy; > + if (PageKsm(page) || page_mapcount(page) != 1 || page_count(page) != 1) { > + unlock_page(page); > goto copy; > - if (!trylock_page(vmf->page)) { > - get_page(vmf->page); > - pte_unmap_unlock(vmf->pte, vmf->ptl); > - lock_page(vmf->page); > - vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, > - vmf->address, &vmf->ptl); > - if (!pte_same(*vmf->pte, vmf->orig_pte)) { > - update_mmu_tlb(vma, vmf->address, vmf->pte); > - unlock_page(vmf->page); > - pte_unmap_unlock(vmf->pte, vmf->ptl); > - put_page(vmf->page); > - return 0; > - } > - put_page(vmf->page); > - } > - if (PageKsm(vmf->page)) { > - bool reused = reuse_ksm_page(vmf->page, vmf->vma, > - vmf->address); > - unlock_page(vmf->page); > - if (!reused) > - goto copy; > - wp_page_reuse(vmf); > - return VM_FAULT_WRITE; > - } > - if (reuse_swap_page(vmf->page, &total_map_swapcount)) { It seems that nobody else calls reuse_swap_page() with total_map_swapcount != NULL. Oleg.