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 E7234C433F5 for ; Tue, 10 May 2022 21:05:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229714AbiEJVFy (ORCPT ); Tue, 10 May 2022 17:05:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38354 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229529AbiEJVFw (ORCPT ); Tue, 10 May 2022 17:05:52 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B96AD193CE; Tue, 10 May 2022 14:05:49 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 88466B81D0E; Tue, 10 May 2022 21:05:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9051EC385C8; Tue, 10 May 2022 21:05:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1652216747; bh=HK/U9ZnYCVJJhfgJnWA8+Meia8HhzwzQcw7dOhhRSYA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=BrzDyZjB5HvQ/Lev6VHmoi8QLWXi1sqqO2eCbz1H5Kb/qtiFlZDGpbFcNkpBziSTz 7vVlUcChs1pklgTI5UQYb7AYjsQHAMwYL2sB+rbc7eWN8ewEIN+i3NnQYGyG322tXw ESstyyt9vP8bP9xx1HH3klVgQidq1/dDTNdIilH4= Date: Tue, 10 May 2022 14:05:45 -0700 From: Andrew Morton To: Yang Shi Cc: vbabka@suse.cz, kirill.shutemov@linux.intel.com, linmiaohe@huawei.com, songliubraving@fb.com, riel@surriel.com, willy@infradead.org, ziy@nvidia.com, tytso@mit.edu, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [v4 PATCH 6/8] mm: khugepaged: make hugepage_vma_check() non-static Message-Id: <20220510140545.5dd9d3145b53cb7e226c236a@linux-foundation.org> In-Reply-To: <20220510203222.24246-7-shy828301@gmail.com> References: <20220510203222.24246-1-shy828301@gmail.com> <20220510203222.24246-7-shy828301@gmail.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, 10 May 2022 13:32:20 -0700 Yang Shi wrote: > The hugepage_vma_check() could be reused by khugepaged_enter() and > khugepaged_enter_vma_merge(), but it is static in khugepaged.c. > Make it non-static and declare it in khugepaged.h. > > .. > > @@ -508,20 +508,13 @@ void __khugepaged_enter(struct mm_struct *mm) > void khugepaged_enter_vma_merge(struct vm_area_struct *vma, > unsigned long vm_flags) > { > - unsigned long hstart, hend; > - > - /* > - * khugepaged only supports read-only files for non-shmem files. > - * khugepaged does not yet work on special mappings. And > - * file-private shmem THP is not supported. > - */ > - if (!hugepage_vma_check(vma, vm_flags)) > - return; > - > - hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; > - hend = vma->vm_end & HPAGE_PMD_MASK; > - if (hstart < hend) > - khugepaged_enter(vma, vm_flags); > + if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) && > + khugepaged_enabled() && > + (((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) < > + (vma->vm_end & HPAGE_PMD_MASK))) { Reviewing these bounds-checking tests is so hard :( Can we simplify? > + if (hugepage_vma_check(vma, vm_flags)) > + __khugepaged_enter(vma->vm_mm); > + } > } void khugepaged_enter_vma(struct vm_area_struct *vma, unsigned long vm_flags) { if (test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags)) return; if (!khugepaged_enabled()) return; if (round_up(vma->vm_start, HPAGE_PMD_SIZE) >= (vma->vm_end & HPAGE_PMD_MASK)) return; /* vma is too small */ if (!hugepage_vma_check(vma, vm_flags)) return; __khugepaged_enter(vma->vm_mm); } Also, it might be slightly faster to have checked MMF_VM_HUGEPAGE before khugepaged_enabled(), but it looks odd. And it might be slower, too - more pointer chasing. I wish someone would document hugepage_vma_check().