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Mon, 21 Dec 2020 07:53:06 -0800 (PST) MIME-Version: 1.0 References: <20201217121303.13386-1-songmuchun@bytedance.com> <20201217121303.13386-4-songmuchun@bytedance.com> <20201221091123.GB14343@linux> <20201221134345.GA19324@linux> In-Reply-To: <20201221134345.GA19324@linux> From: Muchun Song Date: Mon, 21 Dec 2020 23:52:30 +0800 Message-ID: Subject: Re: [External] Re: [PATCH v10 03/11] mm/hugetlb: Free the vmemmap pages associated with each HugeTLB page To: Oscar Salvador Cc: Jonathan Corbet , Mike Kravetz , Thomas Gleixner , mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, Peter Zijlstra , viro@zeniv.linux.org.uk, Andrew Morton , paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, Randy Dunlap , oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, Mina Almasry , David Rientjes , Matthew Wilcox , Michal Hocko , "Song Bao Hua (Barry Song)" , David Hildenbrand , naoya.horiguchi@nec.com, Xiongchun duan , linux-doc@vger.kernel.org, LKML , Linux Memory Management List , linux-fsdevel Content-Type: text/plain; charset="UTF-8" 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 Mon, Dec 21, 2020 at 9:44 PM Oscar Salvador wrote: > > On Mon, Dec 21, 2020 at 07:25:15PM +0800, Muchun Song wrote: > > > Should we add a BUG_ON in vmemmap_remap_free() for now? > > > > BUG_ON(reuse != start + PAGE_SIZE); > > I do not think we have to, plus we would be BUG_ing for some specific use > case in "generic" function. The vmemmap_remap_range() walks page table range [start, end), if reuse is equal to (start + PAGE_SIZE), the range can adjust to [start - PAGE_SIZE, end). But if not, we need some work to implement the "generic" function. - adjust range to [min(start, reuse), end) and call vmemmap_remap_rangeand which skip the hole which is [reuse + PAGE_SIZE, start) or [end, reuse). - call vmemmap_remap_range(reuse, reuse + PAGE_SIZE) to get the reuse page.Then, call vmemmap_remap_range(start, end) again to remap. Which one do you prefer? > Maybe others think different though. > > -- > Oscar Salvador > SUSE L3 -- Yours, Muchun