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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A8884C6FD18 for ; Wed, 19 Apr 2023 04:19:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231652AbjDSETz (ORCPT ); Wed, 19 Apr 2023 00:19:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51594 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229577AbjDSETv (ORCPT ); Wed, 19 Apr 2023 00:19:51 -0400 Received: from mx0a-0031df01.pphosted.com (mx0a-0031df01.pphosted.com [205.220.168.131]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 847341705 for ; Tue, 18 Apr 2023 21:19:50 -0700 (PDT) Received: from pps.filterd (m0279867.ppops.net [127.0.0.1]) by mx0a-0031df01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 33J45ixm023745; Wed, 19 Apr 2023 04:19:35 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=qcppdkim1; bh=fxFKsrUL3l9DMaDGWHS5NCZlebiGDfNwYCxNcetUNBI=; b=V5FMRvugaf4bdoIHuEk4KuRgC7bMQNKKqgTlvbx6HKkvG9eZU54T3NzwdXP7kCtREiId vnWLL8tXV7pEHyQi9PUBRGBvCQWtGXXjQ2y1lqtPR5axa587orvJLe1PaOCyO+ccp5sv kv0oQOu6fCxzY2rJ7eFjatIjD2pvQQr5tuy9tXg9IGZmrp5Kn1MyXmfOWqftwKzQBoeX d/URtWKr82IlNUrqRCYqw8aQbB8ap+5LUhm5ZkmVXBnZCZzvtC1DnsoGunFN1IphRpBQ QlbL9aFwh492XL8q2ODLbQL++Nn4VrkaBGraWfG+WVXgOfB4PTO7KhuTlsVj6Ye0QouR mQ== Received: from nalasppmta05.qualcomm.com (Global_NAT1.qualcomm.com [129.46.96.20]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 3q1w219s5t-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 19 Apr 2023 04:19:35 +0000 Received: from nalasex01a.na.qualcomm.com (nalasex01a.na.qualcomm.com [10.47.209.196]) by NALASPPMTA05.qualcomm.com (8.17.1.5/8.17.1.5) with ESMTPS id 33J4JYU4001769 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 19 Apr 2023 04:19:34 GMT Received: from hu-pkondeti-hyd.qualcomm.com (10.80.80.8) by nalasex01a.na.qualcomm.com (10.47.209.196) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.42; Tue, 18 Apr 2023 21:19:30 -0700 Date: Wed, 19 Apr 2023 09:49:26 +0530 From: Pavan Kondeti To: Frank van der Linden CC: , , , , , , , , , , Subject: Re: [PATCH V7 0/2] mm: shmem: support POSIX_FADV_[WILL|DONT]NEED for shmem files Message-ID: <20230419041926.GA99028@hu-pkondeti-hyd.qualcomm.com> References: <20230418172942.740769-1-fvdl@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20230418172942.740769-1-fvdl@google.com> X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01b.na.qualcomm.com (10.46.141.250) To nalasex01a.na.qualcomm.com (10.47.209.196) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-ORIG-GUID: 6612H3_FDH4H_60UzHBow5lb_5Einqbp X-Proofpoint-GUID: 6612H3_FDH4H_60UzHBow5lb_5Einqbp X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.942,Hydra:6.0.573,FMLib:17.11.170.22 definitions=2023-04-18_17,2023-04-18_01,2023-02-09_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 bulkscore=0 priorityscore=1501 lowpriorityscore=0 impostorscore=0 phishscore=0 mlxscore=0 mlxlogscore=845 malwarescore=0 suspectscore=0 clxscore=1011 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2303200000 definitions=main-2304190039 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 18, 2023 at 05:29:42PM +0000, Frank van der Linden wrote: > Below is a quick patch to allow FADVISE_DONTNEED for shmem to reclaim > mapped pages too. This would fit our usecase, and matches MADV_PAGEOUT > more closely. > > The patch series as posted skips mapped pages even if you remove > the folio_mapped() check, because page_referenced() in > shrink_page_list() will find page tables with the page mapped, > and ignore_references is not set when called from reclaim_pages(). > > You can make this work in a similar fashion to MADV_PAGEOUT by > first unmapping a page, but only if the mapping belongs to > the caller. You just have to change the check for "is there > only one mapping and am I the owner". To do that, change a few > lines in try_to_unmap to allow for checking the mm the mapping > belongs to, and pass in current->mm (NULL still unmaps all mappings). > > I lightly tested this in a somewhat older codebase, so the diff > below isn't fully tested. But if there are no objections to > this approach, we could add it on top of your patchset after > better testing. > > - Frank > > diff --git a/include/linux/rmap.h b/include/linux/rmap.h > index b87d01660412..4403cc2ccc4c 100644 > --- a/include/linux/rmap.h > +++ b/include/linux/rmap.h > @@ -368,6 +368,8 @@ int folio_referenced(struct folio *, int is_locked, > > void try_to_migrate(struct folio *folio, enum ttu_flags flags); > void try_to_unmap(struct folio *, enum ttu_flags flags); > +void try_to_unmap_mm(struct mm_struct *mm, struct folio *folio, > + enum ttu_flags flags); > > int make_device_exclusive_range(struct mm_struct *mm, unsigned long start, > unsigned long end, struct page **pages, > diff --git a/mm/rmap.c b/mm/rmap.c > index 8632e02661ac..4d30e8f5afe2 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1443,6 +1443,11 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma, > munlock_vma_folio(folio, vma, compound); > } > > +struct unmap_arg { > + enum ttu_flags flags; > + struct mm_struct *mm; > +}; > + > /* > * @arg: enum ttu_flags will be passed to this argument > */ > @@ -1455,7 +1460,11 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, > struct page *subpage; > bool anon_exclusive, ret = true; > struct mmu_notifier_range range; > - enum ttu_flags flags = (enum ttu_flags)(long)arg; > + struct unmap_arg *uap = (struct unmap_arg *)arg; > + enum ttu_flags flags = uap->flags; > + > + if (uap->mm && uap->mm != mm) > + return true; > > /* > * When racing against e.g. zap_pte_range() on another cpu, > @@ -1776,6 +1785,7 @@ static int folio_not_mapped(struct folio *folio) > > /** > * try_to_unmap - Try to remove all page table mappings to a folio. > + * @mm: mm to unmap from (NULL to unmap from all) > * @folio: The folio to unmap. > * @flags: action and flags > * > @@ -1785,11 +1795,16 @@ static int folio_not_mapped(struct folio *folio) > * > * Context: Caller must hold the folio lock. > */ > -void try_to_unmap(struct folio *folio, enum ttu_flags flags) > +void try_to_unmap_mm(struct mm_struct *mm, struct folio *folio, > + enum ttu_flags flags) > { > + struct unmap_arg ua = { > + .flags = flags, > + .mm = mm, > + }; > struct rmap_walk_control rwc = { > .rmap_one = try_to_unmap_one, > - .arg = (void *)flags, > + .arg = (void *)&ua, > .done = folio_not_mapped, > .anon_lock = folio_lock_anon_vma_read, > }; > @@ -1800,6 +1815,11 @@ void try_to_unmap(struct folio *folio, enum ttu_flags flags) > rmap_walk(folio, &rwc); > } > > +void try_to_unmap(struct folio *folio, enum ttu_flags flags) > +{ > + try_to_unmap_mm(NULL, folio, flags); > +} > + > /* > * @arg: enum ttu_flags will be passed to this argument. > * > diff --git a/mm/shmem.c b/mm/shmem.c > index 1af85259b6fc..b24af2fb3378 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -2362,8 +2362,24 @@ static void shmem_isolate_pages_range(struct address_space *mapping, loff_t star > > if (!folio_try_get(folio)) > continue; > - if (folio_test_unevictable(folio) || folio_mapped(folio) || > - folio_isolate_lru(folio)) { > + > + if (folio_test_unevictable(folio)) { > + folio_put(folio); > + continue; > + } > + > + /* > + * If the folio is mapped once, try to unmap it from the > + * caller's page table. If it's still mapped afterwards, > + * it belongs to someone else, and we're not going to > + * change someone else's mapping. > + */ > + if (folio_mapcount(folio) == 1 && folio_trylock(folio)) { > + try_to_unmap_mm(current->mm, folio, TTU_BATCH_FLUSH); > + folio_unlock(folio); > + } Is rmap walk can be done from a RCU read critical section which does not allow explicit blocking? Thanks, Pavan