From patchwork Tue Apr 24 04:00:50 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yang Shi X-Patchwork-Id: 10358595 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 0A8B360225 for ; Tue, 24 Apr 2018 04:01:23 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id ED65C28CCF for ; Tue, 24 Apr 2018 04:01:22 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id E163728CD3; Tue, 24 Apr 2018 04:01:22 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00, MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,UNPARSEABLE_RELAY autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7D72328CD1 for ; Tue, 24 Apr 2018 04:01:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750815AbeDXEBS (ORCPT ); Tue, 24 Apr 2018 00:01:18 -0400 Received: from out30-132.freemail.mail.aliyun.com ([115.124.30.132]:37184 "EHLO out30-132.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750731AbeDXEBR (ORCPT ); Tue, 24 Apr 2018 00:01:17 -0400 X-Alimail-AntiSpam: AC=PASS; BC=-1|-1; BR=01201311R271e4; CH=green; FP=0|-1|-1|-1|0|-1|-1|-1; HT=e01e01422; MF=yang.shi@linux.alibaba.com; NM=1; PH=DS; RN=10; SR=0; TI=SMTPD_---0T.lvGxf_1524542450; Received: from e19h19392.et15sqa.tbsite.net(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0T.lvGxf_1524542450) by smtp.aliyun-inc.com(127.0.0.1); Tue, 24 Apr 2018 12:00:57 +0800 From: Yang Shi To: kirill.shutemov@linux.intel.com, hughd@google.com, mhocko@kernel.org, hch@infradead.org, viro@zeniv.linux.org.uk, akpm@linux-foundation.org Cc: yang.shi@linux.alibaba.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [RFC v4 PATCH] mm: shmem: make stat.st_blksize return huge page size if THP is on Date: Tue, 24 Apr 2018 12:00:50 +0800 Message-Id: <1524542450-92577-1-git-send-email-yang.shi@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Since tmpfs THP was supported in 4.8, hugetlbfs is not the only filesystem with huge page support anymore. tmpfs can use huge page via THP when mounting by "huge=" mount option. When applications use huge page on hugetlbfs, it just need check the filesystem magic number, but it is not enough for tmpfs. Make stat.st_blksize return huge page size if it is mounted by appropriate "huge=" option to give applications a hint to optimize the behavior with THP. Some applications may not do wisely with THP. For example, QEMU may mmap file on non huge page aligned hint address with MAP_FIXED, which results in no pages are PMD mapped even though THP is used. Some applications may mmap file with non huge page aligned offset. Both behaviors make THP pointless. statfs.f_bsize still returns 4KB for tmpfs since THP could be split, and it also may fallback to 4KB page silently if there is not enough huge page. Furthermore, different f_bsize makes max_blocks and free_blocks calculation harder but without too much benefit. Returning huge page size via stat.st_blksize sounds good enough. Since PUD size huge page for THP has not been supported, now it just returns HPAGE_PMD_SIZE. Signed-off-by: Yang Shi Cc: "Kirill A. Shutemov" Cc: Hugh Dickins Cc: Michal Hocko Cc: Alexander Viro Suggested-by: Christoph Hellwig --- v3 --> v4: * Rework the commit log per the education from Michal and Kirill * Fix build error if CONFIG_TRANSPARENT_HUGEPAGE is disabled v2 --> v3: * Use shmem_sb_info.huge instead of global variable per Michal's comment v2 --> v1: * Adopted the suggestion from hch to return huge page size via st_blksize instead of creating a new flag. mm/shmem.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/mm/shmem.c b/mm/shmem.c index b859192..19b8055 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -988,6 +988,7 @@ static int shmem_getattr(const struct path *path, struct kstat *stat, { struct inode *inode = path->dentry->d_inode; struct shmem_inode_info *info = SHMEM_I(inode); + struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb); if (info->alloced - info->swapped != inode->i_mapping->nrpages) { spin_lock_irq(&info->lock); @@ -995,6 +996,11 @@ static int shmem_getattr(const struct path *path, struct kstat *stat, spin_unlock_irq(&info->lock); } generic_fillattr(inode, stat); +#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE + if (sbinfo->huge > 0) + stat->blksize = HPAGE_PMD_SIZE; +#endif + return 0; }