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=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 77E6FC433E2 for ; Sat, 29 Aug 2020 09:52:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3A3572075B for ; Sat, 29 Aug 2020 09:52:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=mykernel.net header.i=cgxu519@mykernel.net header.b="f462YgeL" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3A3572075B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=mykernel.net Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 48E206B0006; Sat, 29 Aug 2020 05:52:01 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3F1306B0007; Sat, 29 Aug 2020 05:52:01 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 21C396B0008; Sat, 29 Aug 2020 05:52:01 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0133.hostedemail.com [216.40.44.133]) by kanga.kvack.org (Postfix) with ESMTP id 068256B0006 for ; Sat, 29 Aug 2020 05:52:01 -0400 (EDT) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id B741412E5 for ; Sat, 29 Aug 2020 09:52:00 +0000 (UTC) X-FDA: 77203140000.06.can19_531514e2707d Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin06.hostedemail.com (Postfix) with ESMTP id 7A88010062C94 for ; Sat, 29 Aug 2020 09:52:00 +0000 (UTC) X-HE-Tag: can19_531514e2707d X-Filterd-Recvd-Size: 5986 Received: from sender2-op-o12.zoho.com.cn (sender2-op-o12.zoho.com.cn [163.53.93.243]) by imf12.hostedemail.com (Postfix) with ESMTP for ; Sat, 29 Aug 2020 09:51:59 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; t=1598694691; cv=none; d=zoho.com.cn; s=zohoarc; b=e6IcCG4tFosqzZgL/24g7rTR8CwHArbFn8gqoyeP0usMaoVI6u6AceplXcn6hbW69hHYTCP4L1IzblceuMvXyosITHt8bWStg5jdPiODCObfFX5vScf/wRUodv5P9LVXq2BQ+P5pdYhuWGFGRHyW0s3yKwa2jRkxnEFsqzxXqmo= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com.cn; s=zohoarc; t=1598694691; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:To; bh=ccEWT3RLuwiPMu/BBIgZh5/ZgyfZBB6tStaJtH+L+JY=; b=LyzBXJnBuVVu6950HiaP7Fwrfz5g4BSeqm4kwWZGEa02R+JuXLeSpYdNh90xhJmcsLqMHNeK+VVG3mQtz9x8ZWlBbn++dEft84k6cUUWVmbddciR+BeIk2cVFAMm5Ca79aGeKIQGFhkjneKuNjIkA3AzbtpSVfXxhwmjnYWIZ+k= ARC-Authentication-Results: i=1; mx.zoho.com.cn; dkim=pass header.i=mykernel.net; spf=pass smtp.mailfrom=cgxu519@mykernel.net; dmarc=pass header.from= header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1598694691; s=zohomail; d=mykernel.net; i=cgxu519@mykernel.net; h=From:To:Cc:Message-ID:Subject:Date:In-Reply-To:References:MIME-Version:Content-Transfer-Encoding:Content-Type; bh=ccEWT3RLuwiPMu/BBIgZh5/ZgyfZBB6tStaJtH+L+JY=; b=f462YgeLswSRXtYIq+DvgwbLsEFk5nGTD1bHb+XueyiqlOt1/vAUH/qKwya3brpu 0UF3EModFvQfCwiHAU1nO9n9rnEyxIYz9xWBoNhxRpnMCvdtd+djaZK6y+x2ve6i+SC Mdx1wvDvj8FNOF0UwZi0X/QNCrla4UaH9o2L23AA= Received: from localhost.localdomain (116.30.194.36 [116.30.194.36]) by mx.zoho.com.cn with SMTPS id 1598694689422660.411788621191; Sat, 29 Aug 2020 17:51:29 +0800 (CST) From: Chengguang Xu To: linux-unionfs@vger.kernel.org, linux-mm@kvack.org Cc: miklos@szeredi.hu, akpm@linux-foundation.org, amir73il@gmail.com, riteshh@linux.ibm.com, Chengguang Xu Message-ID: <20200829095101.25350-2-cgxu519@mykernel.net> Subject: [RFC PATCH 1/3] mm: mmap: export necessary functions for overlayfs' mmap Date: Sat, 29 Aug 2020 17:50:59 +0800 X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200829095101.25350-1-cgxu519@mykernel.net> References: <20200829095101.25350-1-cgxu519@mykernel.net> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ZohoCNMailClient: External Content-Type: text/plain; charset=utf8 X-Rspamd-Queue-Id: 7A88010062C94 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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: In shared mode mmap, if overlayfs' inode does not have data in upper layer, it should call maybe_unlock_mmap_for_io() to release lock and waiting for IO in ->fault handler. Meanwhile, in order to avoid endless retry we should also check flag FAULT_FLAG_TRIED carefully in ->fault handler. Signed-off-by: Chengguang Xu --- include/linux/mm.h | 2 ++ mm/filemap.c | 28 ++++++++++++++++++++++++++++ mm/internal.h | 22 ---------------------- 3 files changed, 30 insertions(+), 22 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index dc7b87310c10..214b23734eed 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1656,6 +1656,8 @@ void unmap_mapping_pages(struct address_space *mappin= g, =09=09pgoff_t start, pgoff_t nr, bool even_cows); void unmap_mapping_range(struct address_space *mapping, =09=09loff_t const holebegin, loff_t const holelen, int even_cows); +struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf, struct file *f= pin); +bool fault_flag_check(struct vm_fault *vmf, unsigned int flag); #else static inline vm_fault_t handle_mm_fault(struct vm_area_struct *vma, =09=09unsigned long address, unsigned int flags) diff --git a/mm/filemap.c b/mm/filemap.c index f0ae9a6308cb..8a226f8ca262 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2704,6 +2704,34 @@ int generic_file_readonly_mmap(struct file *file, st= ruct vm_area_struct *vma) =09=09return -EINVAL; =09return generic_file_mmap(file, vma); } + +struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf, +=09=09=09=09 struct file *fpin) +{ +=09int flags =3D vmf->flags; + +=09if (fpin) +=09=09return fpin; + +=09/* +=09 * FAULT_FLAG_RETRY_NOWAIT means we don't want to wait on page locks or +=09 * anything, so we only pin the file and drop the mmap_lock if only +=09 * FAULT_FLAG_ALLOW_RETRY is set, while this is the first attempt. +=09 */ +=09if (fault_flag_allow_retry_first(flags) && +=09 !(flags & FAULT_FLAG_RETRY_NOWAIT)) { +=09=09fpin =3D get_file(vmf->vma->vm_file); +=09=09mmap_read_unlock(vmf->vma->vm_mm); +=09} +=09return fpin; +} +EXPORT_SYMBOL(maybe_unlock_mmap_for_io); + +bool fault_flag_check(struct vm_fault *vmf, unsigned int flag) +{ +=09return vmf->flags & flag; +} +EXPORT_SYMBOL(fault_flag_check); #else vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf) { diff --git a/mm/internal.h b/mm/internal.h index 9886db20d94f..ef19235c6bf1 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -402,28 +402,6 @@ vma_address(struct page *page, struct vm_area_struct *= vma) =20 =09return max(start, vma->vm_start); } - -static inline struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf, -=09=09=09=09=09=09 struct file *fpin) -{ -=09int flags =3D vmf->flags; - -=09if (fpin) -=09=09return fpin; - -=09/* -=09 * FAULT_FLAG_RETRY_NOWAIT means we don't want to wait on page locks or -=09 * anything, so we only pin the file and drop the mmap_lock if only -=09 * FAULT_FLAG_ALLOW_RETRY is set, while this is the first attempt. -=09 */ -=09if (fault_flag_allow_retry_first(flags) && -=09 !(flags & FAULT_FLAG_RETRY_NOWAIT)) { -=09=09fpin =3D get_file(vmf->vma->vm_file); -=09=09mmap_read_unlock(vmf->vma->vm_mm); -=09} -=09return fpin; -} - #else /* !CONFIG_MMU */ static inline void clear_page_mlock(struct page *page) { } static inline void mlock_vma_page(struct page *page) { } --=20 2.20.1