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Date: Tue, 22 Dec 2020 10:49:35 +0800 From: Muchun Song <songmuchun@...edance.com> To: Oscar Salvador <osalvador@...e.de> Cc: Jonathan Corbet <corbet@....net>, Mike Kravetz <mike.kravetz@...cle.com>, Thomas Gleixner <tglx@...utronix.de>, mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com, dave.hansen@...ux.intel.com, luto@...nel.org, Peter Zijlstra <peterz@...radead.org>, viro@...iv.linux.org.uk, Andrew Morton <akpm@...ux-foundation.org>, paulmck@...nel.org, mchehab+huawei@...nel.org, pawan.kumar.gupta@...ux.intel.com, Randy Dunlap <rdunlap@...radead.org>, oneukum@...e.com, anshuman.khandual@....com, jroedel@...e.de, Mina Almasry <almasrymina@...gle.com>, David Rientjes <rientjes@...gle.com>, Matthew Wilcox <willy@...radead.org>, Michal Hocko <mhocko@...e.com>, "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>, David Hildenbrand <david@...hat.com>, naoya.horiguchi@....com, Xiongchun duan <duanxiongchun@...edance.com>, linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>, Linux Memory Management List <linux-mm@...ck.org>, linux-fsdevel <linux-fsdevel@...r.kernel.org> Subject: Re: [External] Re: [PATCH v10 03/11] mm/hugetlb: Free the vmemmap pages associated with each HugeTLB page On Tue, Dec 22, 2020 at 2:00 AM Oscar Salvador <osalvador@...e.de> wrote: > > On Mon, Dec 21, 2020 at 11:52:30PM +0800, Muchun Song wrote: > > On Mon, Dec 21, 2020 at 9:44 PM Oscar Salvador <osalvador@...e.de> 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? > > I would not overcomplicate things at this stage. > Just follow my sugestion and add a BUG_ON as you said, that might be the > easier way now. > We can overthink this in the future when some other usecases come > around, right? You are right. Will do this. Thanks for your suggestions. > > Thanks > > > -- > Oscar Salvador > SUSE L3 -- Yours, Muchun
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