From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4FF27C32750 for ; Tue, 13 Aug 2019 14:50:38 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id EFABE20844 for ; Tue, 13 Aug 2019 14:50:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EFABE20844 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=hpe.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 7DA0B6B000A; Tue, 13 Aug 2019 10:50:37 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 78AA86B000C; Tue, 13 Aug 2019 10:50:37 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 679456B000D; Tue, 13 Aug 2019 10:50:37 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0076.hostedemail.com [216.40.44.76]) by kanga.kvack.org (Postfix) with ESMTP id 421606B000A for ; Tue, 13 Aug 2019 10:50:37 -0400 (EDT) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id D8D7B8248AA1 for ; Tue, 13 Aug 2019 14:50:36 +0000 (UTC) X-FDA: 75817690872.16.salt43_79b1185617043 X-HE-Tag: salt43_79b1185617043 X-Filterd-Recvd-Size: 9078 Received: from mx0b-002e3701.pphosted.com (mx0b-002e3701.pphosted.com [148.163.143.35]) by imf28.hostedemail.com (Postfix) with ESMTP for ; Tue, 13 Aug 2019 14:50:36 +0000 (UTC) Received: from pps.filterd (m0150245.ppops.net [127.0.0.1]) by mx0b-002e3701.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x7DEfI83009101; Tue, 13 Aug 2019 14:50:31 GMT Received: from g2t2354.austin.hpe.com (g2t2354.austin.hpe.com [15.233.44.27]) by mx0b-002e3701.pphosted.com with ESMTP id 2ubwwp8qrs-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 13 Aug 2019 14:50:31 +0000 Received: from g2t2360.austin.hpecorp.net (g2t2360.austin.hpecorp.net [16.196.225.135]) by g2t2354.austin.hpe.com (Postfix) with ESMTP id B3DF9AE; Tue, 13 Aug 2019 14:50:30 +0000 (UTC) Received: from hpe.com (teo-eag.americas.hpqcorp.net [10.33.152.10]) by g2t2360.austin.hpecorp.net (Postfix) with ESMTP id E0DF13B; Tue, 13 Aug 2019 14:50:29 +0000 (UTC) Date: Tue, 13 Aug 2019 09:50:29 -0500 From: Dimitri Sivanich To: Bharath Vedartham Cc: jhubbard@nvidia.com, gregkh@linuxfoundation.org, sivanich@hpe.com, arnd@arndb.de, ira.weiny@intel.com, jglisse@redhat.com, william.kucharski@oracle.com, hch@lst.de, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kernel-mentees@lists.linuxfoundation.org Subject: Re: [Linux-kernel-mentees][PATCH v5 1/1] sgi-gru: Remove *pte_lookup functions, Convert to get_user_page*() Message-ID: <20190813145029.GA32451@hpe.com> References: <1565379497-29266-1-git-send-email-linux.bhar@gmail.com> <1565379497-29266-2-git-send-email-linux.bhar@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <1565379497-29266-2-git-send-email-linux.bhar@gmail.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-HPE-SCL: -1 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-08-13_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908130156 Content-Transfer-Encoding: quoted-printable 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: Bharath, I do not believe that __get_user_pages_fast will work for the atomic case= , as there is no guarantee that the 'current->mm' will be the correct one for = the process in question, as the process might have moved away from the cpu th= at is handling interrupts for it's context. On Sat, Aug 10, 2019 at 01:08:17AM +0530, Bharath Vedartham wrote: > For pages that were retained via get_user_pages*(), release those pages > via the new put_user_page*() routines, instead of via put_page() or > release_pages(). >=20 > This is part a tree-wide conversion, as described in commit fc1d8e7cca2= d > ("mm: introduce put_user_page*(), placeholder versions"). >=20 > As part of this conversion, the *pte_lookup functions can be removed an= d > be easily replaced with get_user_pages_fast() functions. In the case of > atomic lookup, __get_user_pages_fast() is used, because it does not fal= l > back to the slow path: get_user_pages(). get_user_pages_fast(), on the = other > hand, first calls __get_user_pages_fast(), but then falls back to the > slow path if __get_user_pages_fast() fails. >=20 > Also: remove unnecessary CONFIG_HUGETLB ifdefs. >=20 > Cc: Ira Weiny > Cc: John Hubbard > Cc: J=E9r=F4me Glisse > Cc: Greg Kroah-Hartman > Cc: Dimitri Sivanich > Cc: Arnd Bergmann > Cc: William Kucharski > Cc: Christoph Hellwig > Cc: linux-kernel@vger.kernel.org > Cc: linux-mm@kvack.org > Cc: linux-kernel-mentees@lists.linuxfoundation.org > Reviewed-by: Ira Weiny > Reviewed-by: John Hubbard > Reviewed-by: William Kucharski > Signed-off-by: Bharath Vedartham > --- > This is a fold of the 3 patches in the v2 patch series. > The review tags were given to the individual patches. >=20 > Changes since v3 > - Used gup flags in get_user_pages_fast rather than > boolean flags. > Changes since v4 > - Updated changelog according to John Hubbard. > --- > drivers/misc/sgi-gru/grufault.c | 112 +++++++++-----------------------= -------- > 1 file changed, 24 insertions(+), 88 deletions(-) >=20 > diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/gru= fault.c > index 4b713a8..304e9c5 100644 > --- a/drivers/misc/sgi-gru/grufault.c > +++ b/drivers/misc/sgi-gru/grufault.c > @@ -166,96 +166,20 @@ static void get_clear_fault_map(struct gru_state = *gru, > } > =20 > /* > - * Atomic (interrupt context) & non-atomic (user context) functions to > - * convert a vaddr into a physical address. The size of the page > - * is returned in pageshift. > - * returns: > - * 0 - successful > - * < 0 - error code > - * 1 - (atomic only) try again in non-atomic context > - */ > -static int non_atomic_pte_lookup(struct vm_area_struct *vma, > - unsigned long vaddr, int write, > - unsigned long *paddr, int *pageshift) > -{ > - struct page *page; > - > -#ifdef CONFIG_HUGETLB_PAGE > - *pageshift =3D is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > -#else > - *pageshift =3D PAGE_SHIFT; > -#endif > - if (get_user_pages(vaddr, 1, write ? FOLL_WRITE : 0, &page, NULL) <=3D= 0) > - return -EFAULT; > - *paddr =3D page_to_phys(page); > - put_page(page); > - return 0; > -} > - > -/* > - * atomic_pte_lookup > + * mmap_sem is already helod on entry to this function. This guarantee= s > + * existence of the page tables. > * > - * Convert a user virtual address to a physical address > * Only supports Intel large pages (2MB only) on x86_64. > - * ZZZ - hugepage support is incomplete > - * > - * NOTE: mmap_sem is already held on entry to this function. This > - * guarantees existence of the page tables. > + * ZZZ - hugepage support is incomplete. > */ > -static int atomic_pte_lookup(struct vm_area_struct *vma, unsigned long= vaddr, > - int write, unsigned long *paddr, int *pageshift) > -{ > - pgd_t *pgdp; > - p4d_t *p4dp; > - pud_t *pudp; > - pmd_t *pmdp; > - pte_t pte; > - > - pgdp =3D pgd_offset(vma->vm_mm, vaddr); > - if (unlikely(pgd_none(*pgdp))) > - goto err; > - > - p4dp =3D p4d_offset(pgdp, vaddr); > - if (unlikely(p4d_none(*p4dp))) > - goto err; > - > - pudp =3D pud_offset(p4dp, vaddr); > - if (unlikely(pud_none(*pudp))) > - goto err; > - > - pmdp =3D pmd_offset(pudp, vaddr); > - if (unlikely(pmd_none(*pmdp))) > - goto err; > -#ifdef CONFIG_X86_64 > - if (unlikely(pmd_large(*pmdp))) > - pte =3D *(pte_t *) pmdp; > - else > -#endif > - pte =3D *pte_offset_kernel(pmdp, vaddr); > - > - if (unlikely(!pte_present(pte) || > - (write && (!pte_write(pte) || !pte_dirty(pte))))) > - return 1; > - > - *paddr =3D pte_pfn(pte) << PAGE_SHIFT; > -#ifdef CONFIG_HUGETLB_PAGE > - *pageshift =3D is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT; > -#else > - *pageshift =3D PAGE_SHIFT; > -#endif > - return 0; > - > -err: > - return 1; > -} > - > static int gru_vtop(struct gru_thread_state *gts, unsigned long vaddr, > int write, int atomic, unsigned long *gpa, int *pageshift) > { > struct mm_struct *mm =3D gts->ts_mm; > struct vm_area_struct *vma; > unsigned long paddr; > - int ret, ps; > + int ret; > + struct page *page; > =20 > vma =3D find_vma(mm, vaddr); > if (!vma) > @@ -263,21 +187,33 @@ static int gru_vtop(struct gru_thread_state *gts,= unsigned long vaddr, > =20 > /* > * Atomic lookup is faster & usually works even if called in non-atom= ic > - * context. > + * context. get_user_pages_fast does atomic lookup before falling bac= k to > + * slow gup. > */ > rmb(); /* Must/check ms_range_active before loading PTEs */ > - ret =3D atomic_pte_lookup(vma, vaddr, write, &paddr, &ps); > - if (ret) { > - if (atomic) > + if (atomic) { > + ret =3D __get_user_pages_fast(vaddr, 1, write, &page); > + if (!ret) > goto upm; > - if (non_atomic_pte_lookup(vma, vaddr, write, &paddr, &ps)) > + } else { > + ret =3D get_user_pages_fast(vaddr, 1, write ? FOLL_WRITE : 0, &page)= ; > + if (!ret) > goto inval; > } > + > + paddr =3D page_to_phys(page); > + put_user_page(page); > + > + if (unlikely(is_vm_hugetlb_page(vma))) > + *pageshift =3D HPAGE_SHIFT; > + else > + *pageshift =3D PAGE_SHIFT; > + > if (is_gru_paddr(paddr)) > goto inval; > - paddr =3D paddr & ~((1UL << ps) - 1); > + paddr =3D paddr & ~((1UL << *pageshift) - 1); > *gpa =3D uv_soc_phys_ram_to_gpa(paddr); > - *pageshift =3D ps; > + > return VTOP_SUCCESS; > =20 > inval: > --=20 > 2.7.4 >=20