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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7243EE732C9 for ; Thu, 28 Sep 2023 11:59:50 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D6B698D007E; Thu, 28 Sep 2023 07:59:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D1AD68D0038; Thu, 28 Sep 2023 07:59:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C31388D007E; Thu, 28 Sep 2023 07:59:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id B4B5D8D0038 for ; Thu, 28 Sep 2023 07:59:49 -0400 (EDT) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 89BB3B3792 for ; Thu, 28 Sep 2023 11:59:49 +0000 (UTC) X-FDA: 81285862098.05.BE1F76C Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf10.hostedemail.com (Postfix) with ESMTP id 70CC4C0011 for ; Thu, 28 Sep 2023 11:59:47 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf10.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1695902387; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=eErpPbAfD0HzNbDWCSq0NqTvXCcidCAJPs5lDgztij4=; b=FAioQpwH13bQ54TxovA1CSBaWS4pfXEaYr7qtPUuOEJ919q64lSL59ZC0ECJkNuevZxBqK pwVjbfi8vlRDn77dMv5LqZ6Ukza7XTwLI6XOwhQKBzOSwRQBwf8LUj3lcSJYkOEdrA155o nR3JyH61WLYn8L6ax+2SG6TxBfPF6n0= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf10.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1695902387; a=rsa-sha256; cv=none; b=jUws1pKcVkAiUqt8KLMAljPwgY8IizGgW1wbw19VS+Y6tF+sWAf7GtksJdSq+1pc5bCb9K X3EXpDm2WlVFQnkEfKzL7tiuOTfmwLVQ3oibiePNTFd43nVk0kLxHAmFE4742l+0dU5AZw Hd9lshe4JNWtUgfUywZIr/kB1lEnbMg= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A25D51FB; Thu, 28 Sep 2023 05:00:24 -0700 (PDT) Received: from [10.1.37.161] (XHFQ2J9959.cambridge.arm.com [10.1.37.161]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id EF6F23F5A1; Thu, 28 Sep 2023 04:59:44 -0700 (PDT) Message-ID: <54e5accf-1a56-495a-a4f5-d57504bc2fc8@arm.com> Date: Thu, 28 Sep 2023 12:59:43 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: BUG: MADV_COLLAPSE doesn't work for XFS files Content-Language: en-GB To: Bagas Sanjaya , Hugh Dickins , David Hildenbrand , Matthew Wilcox , zokeefe@google.com, Chandan Babu R , "Darrick J. Wong" Cc: Linux Memory Management List , Linux XFS , Linux Kernel Mailing List References: <4d6c9b19-cdbb-4a00-9a40-5ed5c36332e5@arm.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 70CC4C0011 X-Stat-Signature: okhnhzhiswo3fpq4typ77ish7tnm5sok X-HE-Tag: 1695902387-930942 X-HE-Meta: U2FsdGVkX1997Cz58KW8ss+TPq3EoAFttnEkXfn+/Rwk8oD+rYOAtdHsloxJEuUk0pJXqgt8msFvx29jFbNAaBT0N43Z8HSZCOfo7VXjnmtnGGfL7fHj5pEzSc0ENXVUlU9U5j12jNldYv3qjOxwXXSX63AI8rdicYzEH7MzFA/Bz6iGSwlXYA11TU7lcEJ2Qq81enLde8tGKT5i1EKx7jFNI+ICG7OADQ0s4rVrjXcM7Ok8xyesAxD7cx5KV53v89kOz8j96ysMLKtPGin5rjIHYcGt6ak8+9XuScwc8koKHleRnqqkulNy9tuTGFdhoowle8/I0M7aAUQp+AWn+iWi8Pi5p10UKPdv6byqexglXBwF2FJTjeT0exrPGfF9olFnPqSv9UBFCgwq+zygOpnGW2/6miXB7Ykfp84Q/njll489bpd32nJus15oddOr6NhJjCXYycop6e3OnWeo7di67tyXc5KM4wRLrDy7k323tgfYoam9aj18mVPX1MyQBC2vEakfNlZki9/5o75XdS6fSmvyU8cBPuRmF2E30786vb5XkBCQEArOFD5ndu73w5IPhHg/z17D8ghno7ZtOlo8Vd76I24mcAp+j0okRx1EZ0E7oGimongMkZU8YeiObf+1+MP5yGppIZ103k0dAC8VSdAoB5WOh5ICrbyIhjVcM4tlzKfwp26XtmudSgrntAHjxKF0Eyvo8cVYo0i8O1Xqebm0oUiSPzPpffwgztuv/MW7tjkr/CADrz7t1tF+dBXGIh8PJRH+yz+SvzNvk7CqrjzBdh8LAxKAWByLo2LXe+7c1Z1taY/CmrbmCP0hFFAHwCWHCDOmmorssvMH36wlmy/mc5slHabfhiGY8DaqAm8ernbWMXRjH3TSNa9bkX6p8njJrKkC1Z7fpDd4BLWebHFWoeD+ze5zWcwMBHxftOy/HTAv/4sAWXZTFxMUvYrwBkuIsX3mOcy4VhY lfQmCQXS 3ovuT+A+TIWe1glwyBp8zEPUF80cR0sF7lsvn9I3z7OH84zZR7HMKXvazIQJp4BBImwGACYYLy5uVTRzPbidJcoMd9tDLfzk1MY2qcyWud52d99V53lk5TqmyQNdoOV64uER413VkUphFLRawS395GhKwbKzEI7CBnIXzeoBuowLT0o0nC7ZVxyG56nzIN2CsXy/r 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: On 28/09/2023 11:54, Bagas Sanjaya wrote: > On Thu, Sep 28, 2023 at 10:55:17AM +0100, Ryan Roberts wrote: >> Hi all, >> >> I've just noticed that when applied to a file mapping for a file on xfs, MADV_COLLAPSE returns EINVAL. The same test case works fine if the file is on ext4. >> >> I think the root cause is that the implementation bails out if it finds a (non-PMD-sized) large folio in the page cache for any part of the file covered by the region. XFS does readahead into large folios so we hit this issue. See khugepaged.h:collapse_file(): >> >> if (PageTransCompound(page)) { >> struct page *head = compound_head(page); >> >> result = compound_order(head) == HPAGE_PMD_ORDER && >> head->index == start >> /* Maybe PMD-mapped */ >> ? SCAN_PTE_MAPPED_HUGEPAGE >> : SCAN_PAGE_COMPOUND; >> goto out_unlock; >> } > > I don't see any hint to -EINVAL above. Am I missing something? The SCAN_PAGE_COMPOUND result ends up back at madvise_collapse() where it eventually gets converted to -EINVAL by madvise_collapse_errno(). > >> >> I'm not sure if this is already a known issue? I don't have time to work on a fix for this right now, so thought I would highlight it at least. I might get around to it at some point in the future if nobody else tackles it. >> >> Thanks, >> Ryan >> >> >> Test case I've been using: >> >> -->8-- >> >> #include >> #include >> #include >> #include >> #include >> #include >> #include >> >> #ifndef MADV_COLLAPSE >> #define MADV_COLLAPSE 25 >> #endif >> >> #define handle_error(msg) do { perror(msg); exit(EXIT_FAILURE); } while (0) >> >> #define SZ_1K 1024 >> #define SZ_1M (SZ_1K * SZ_1K) >> #define ALIGN(val, align) (((val) + ((align) - 1)) & ~((align) - 1)) >> >> #if 1 >> // ext4 >> #define DATA_FILE "/home/ubuntu/data.txt" >> #else >> // xfs >> #define DATA_FILE "/boot/data.txt" >> #endif >> >> int main(void) >> { >> int fd; >> char *mem; >> int ret; >> >> fd = open(DATA_FILE, O_RDONLY); >> if (fd == -1) >> handle_error("open"); >> >> mem = mmap(NULL, SZ_1M * 4, PROT_READ | PROT_EXEC, MAP_PRIVATE, fd, 0); >> close(fd); >> if (mem == MAP_FAILED) >> handle_error("mmap"); >> >> printf("1: pid=%d, mem=%p\n", getpid(), mem); >> getchar(); >> >> mem = (char *)ALIGN((unsigned long)mem, SZ_1M * 2); >> ret = madvise(mem, SZ_1M * 2, MADV_COLLAPSE); >> if (ret) >> handle_error("madvise"); >> >> printf("2: pid=%d, mem=%p\n", getpid(), mem); >> getchar(); >> >> return 0; >> } >> >> -->8-- >> > > Confused... This is a user space test case that shows the problem; data.txt needs to be at least 4MB and on a mounted ext4 and xfs filesystem. By toggling the '#if 1' to 0, you can see the different behaviours for ext4 and xfs - handle_error("madvise") fires with EINVAL in the xfs case. The getchar()s are leftovers from me looking at the smaps file. >