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[209.85.220.65]) by mx.google.com with SMTPS id n129sor24246469jaa.12.2019.03.22.15.13.06 for (Google Transport Security); Fri, 22 Mar 2019 15:13:06 -0700 (PDT) Received-SPF: pass (google.com: domain of dan.j.williams@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@intel-com.20150623.gappssmtp.com header.s=20150623 header.b=Zb9Bl7Bn; spf=pass (google.com: domain of dan.j.williams@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=dan.j.williams@gmail.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=VnWfr5Cz9g8Ts5McgdJK3bb2nMan4nq5nXqWONnMsfs=; b=Zb9Bl7Bn4sqZs4rM2mwfzJd7rKnn+/+6ONyGGwJqa1scMrXWXjmi9yoQBAbfMlLpgS RGV1LtFJyFJAtRyqt7x4phr5CYLMLHxyjOqtaGBIgKlABbih3LbLp5n0OYCbWIHRLaHd TTQ98w8krLJnK39QE8Dp0ik11E8+01Sgyn1wW72V9bUGSzJ08oA4QbCqRZA5AnJQLOtm o3basMsLTQYqNorbmDjd4KoyjPrND/z4P2rEoZfVYQnDMfAEdcsp9b63663QinvyZoJp HOu5mHwb07RCBU+1v7ChvrPznU5/HmjF8OEnSTsQgs+cld8MrdbVwNZKadLpnlT93nHs Yb2w== X-Google-Smtp-Source: APXvYqwPCPjaWzKVXpURWg65K5fkBoLbrluPEoFqqgn2rT6o/InM1ko8UbBUfBaLU8H/oERd+79+VhkVDmrMWUaE2i4= X-Received: by 2002:a02:c007:: with SMTP id y7mr8517902jai.1.1553292786464; Fri, 22 Mar 2019 15:13:06 -0700 (PDT) MIME-Version: 1.0 References: <20190317183438.2057-1-ira.weiny@intel.com> <20190317183438.2057-5-ira.weiny@intel.com> In-Reply-To: <20190317183438.2057-5-ira.weiny@intel.com> From: Dan Williams Date: Fri, 22 Mar 2019 15:12:55 -0700 Message-ID: Subject: Re: [RESEND 4/7] mm/gup: Add FOLL_LONGTERM capability to GUP fast To: ira.weiny@intel.com Cc: Andrew Morton , John Hubbard , Michal Hocko , "Kirill A. Shutemov" , Peter Zijlstra , Jason Gunthorpe , Benjamin Herrenschmidt , Paul Mackerras , "David S. Miller" , Martin Schwidefsky , Heiko Carstens , Rich Felker , Yoshinori Sato , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Ralf Baechle , James Hogan , linux-mm , Linux Kernel Mailing List , linux-mips@vger.kernel.org, linuxppc-dev , linux-s390 , Linux-sh , sparclinux@vger.kernel.org, linux-rdma@vger.kernel.org, "netdev@vger.kernel.org" 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 Sun, Mar 17, 2019 at 7:36 PM wrote: > > From: Ira Weiny > > DAX pages were previously unprotected from longterm pins when users > called get_user_pages_fast(). > > Use the new FOLL_LONGTERM flag to check for DEVMAP pages and fall > back to regular GUP processing if a DEVMAP page is encountered. > > Signed-off-by: Ira Weiny > --- > mm/gup.c | 29 +++++++++++++++++++++++++---- > 1 file changed, 25 insertions(+), 4 deletions(-) > > diff --git a/mm/gup.c b/mm/gup.c > index 0684a9536207..173db0c44678 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1600,6 +1600,9 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, > goto pte_unmap; > > if (pte_devmap(pte)) { > + if (unlikely(flags & FOLL_LONGTERM)) > + goto pte_unmap; > + > pgmap = get_dev_pagemap(pte_pfn(pte), pgmap); > if (unlikely(!pgmap)) { > undo_dev_pagemap(nr, nr_start, pages); > @@ -1739,8 +1742,11 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, > if (!pmd_access_permitted(orig, flags & FOLL_WRITE)) > return 0; > > - if (pmd_devmap(orig)) > + if (pmd_devmap(orig)) { > + if (unlikely(flags & FOLL_LONGTERM)) > + return 0; > return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr); > + } > > refs = 0; > page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); > @@ -1777,8 +1783,11 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, > if (!pud_access_permitted(orig, flags & FOLL_WRITE)) > return 0; > > - if (pud_devmap(orig)) > + if (pud_devmap(orig)) { > + if (unlikely(flags & FOLL_LONGTERM)) > + return 0; > return __gup_device_huge_pud(orig, pudp, addr, end, pages, nr); > + } > > refs = 0; > page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); > @@ -2066,8 +2075,20 @@ int get_user_pages_fast(unsigned long start, int nr_pages, > start += nr << PAGE_SHIFT; > pages += nr; > > - ret = get_user_pages_unlocked(start, nr_pages - nr, pages, > - gup_flags); > + if (gup_flags & FOLL_LONGTERM) { > + down_read(¤t->mm->mmap_sem); > + ret = __gup_longterm_locked(current, current->mm, > + start, nr_pages - nr, > + pages, NULL, gup_flags); > + up_read(¤t->mm->mmap_sem); > + } else { > + /* > + * retain FAULT_FOLL_ALLOW_RETRY optimization if > + * possible > + */ > + ret = get_user_pages_unlocked(start, nr_pages - nr, > + pages, gup_flags); I couldn't immediately grok why this path needs to branch on FOLL_LONGTERM? Won't get_user_pages_unlocked(..., FOLL_LONGTERM) do the right thing?