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Fri, 29 Jan 2021 17:22:27 -0800 (PST) Received: from google.com ([2620:15c:211:201:b81c:be0c:d615:b5bb]) by smtp.gmail.com with ESMTPSA id p2sm10193766pgl.19.2021.01.29.17.22.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 29 Jan 2021 17:22:26 -0800 (PST) Date: Fri, 29 Jan 2021 17:22:24 -0800 From: Minchan Kim To: Matthew Wilcox Cc: hughd@google.com, kirill@shutemov.name, linux-mm Subject: Re: THP handling with driver compound page on fault Message-ID: References: <20210130010002.GE308988@casper.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210130010002.GE308988@casper.infradead.org> 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: Hi Mattew, On Sat, Jan 30, 2021 at 01:00:02AM +0000, Matthew Wilcox wrote: > On Fri, Jan 29, 2021 at 04:13:07PM -0800, Minchan Kim wrote: > > A custom driver overrides (vm_operations_struct.fault) and map their > > compound page(__GFP_COMP) to page table on userprocess on demand. > > You're looking to backport: > > commit d01ac3c35214ce362f50cada37cb7bab8c801896 > Author: Matthew Wilcox (Oracle) > Date: Thu Oct 15 20:05:26 2020 -0700 > > mm/memory: remove page fault assumption of compound page size > I guess you meant the check below. if (compound_order(page) != HPAGE_PMD_ORDER) What happens if driver allcoated HPAGE_PMD_ORDER size?