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 C8417C05027 for ; Fri, 20 Jan 2023 18:27:13 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0B42F6B0071; Fri, 20 Jan 2023 13:27:13 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 064066B0081; Fri, 20 Jan 2023 13:27:13 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E49056B0082; Fri, 20 Jan 2023 13:27:12 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id D35706B0071 for ; Fri, 20 Jan 2023 13:27:12 -0500 (EST) Received: from smtpin18.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 7ACBFAB541 for ; Fri, 20 Jan 2023 18:27:12 +0000 (UTC) X-FDA: 80376009504.18.82AF8EC Received: from mail-qk1-f179.google.com (mail-qk1-f179.google.com [209.85.222.179]) by imf17.hostedemail.com (Postfix) with ESMTP id B4FB340006 for ; Fri, 20 Jan 2023 18:27:10 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=IfDIWfPY; spf=pass (imf17.hostedemail.com: domain of nphamcs@gmail.com designates 209.85.222.179 as permitted sender) smtp.mailfrom=nphamcs@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1674239230; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=xHL87ld3fhJK3FBOZCvDaUreZbi4ooyG7eGSrOm7Go4=; b=fig53UyzBSzzEK3W6oy22UTGansViHAKBTHr0LWxG84anpR/DBZE18CpJ1WQt/SkOkdQdi 9WHQo4paygbyuVOX3EPnDK6440A04hc5/p6XwfeyYEPGoLROhB2K0Kv0FqdcUe2NWEaBDu pGRe0la3f/+5peyIRTI/VaX6qGUISuA= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=IfDIWfPY; spf=pass (imf17.hostedemail.com: domain of nphamcs@gmail.com designates 209.85.222.179 as permitted sender) smtp.mailfrom=nphamcs@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1674239230; a=rsa-sha256; cv=none; b=bvJxYuvEWprUzxsnVrdvetXGX0WoXPzaP07nn+VAI064Vs93KYX6PdTNiKfn6pC6M626mP BV8Z+XTNK+4SEZlRAvhMpjcpv2p9Mhq/emfOzqOAkhqC5uMtrLKpdBrTgLiWWZ4TQjTbYj yH2bBqGrCNSShZWhOH/VA77TJ63EFJU= Received: by mail-qk1-f179.google.com with SMTP id z9so3323531qkl.13 for ; Fri, 20 Jan 2023 10:27:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=xHL87ld3fhJK3FBOZCvDaUreZbi4ooyG7eGSrOm7Go4=; b=IfDIWfPYYKZcdJ/me74bxWUAH2vcXwJrlwkrFCHwD1h0/SNAMx2Iha4XORYmPF4kWP GrFZKshnR+dYpV/MFvMcsPg1vq4TUHC3nCqyNKXwwLCaDHZ6Zl/d4FN0lFHFUASHF6QC U6G3O0yeyVkXGC3hAtXYytKj0lV2TemqD6rkyvXWGKKDjzP7p2zyL8jVHcycYMY6nTl6 qT6TzSCo42NEVPcOjZLhTALGEMkb//7y8dCuG9883qrZ8sJDDyid6ydpnr/j6Z5LMHGa ilQM64Eb71VGvwKCVXoNXyaAVa8Gyvdm1H0sgDQ5tN7UZitBrUe9R4YtWbf2ikI8vzer a9bA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=xHL87ld3fhJK3FBOZCvDaUreZbi4ooyG7eGSrOm7Go4=; b=1i/ZyM+aH5YJy1SXMTjToGT0HwXxNSuWeZNcAcvIe8Rc3Dj8u0/urqD5y6TLJ4noup BNx17JKAWs1AP4HD7ntvDLu6S4rBVWuNBC3mb1MbjIOHP/0JtYWSdac+EL+QGNA+u93S TH5xjwv8gVOmFewixvdkzsxln7YL93WXfp/byfJxPRRNvp+b7gn+SEU5ZKucYh4J5OAU HT4F2X0Kjcym7/ANk1gizFd55aEkgWZp9SLwcB9dK/R/5IHnOZ7ONQxmqPdHgrqTUas6 FM8OrNzs8b4o5qqUoCOuurgPahZaLoGuyWgotm5i74IjG88ZjPxHtuMh0eG9NGajwvjf VNlA== X-Gm-Message-State: AFqh2ko4XbGuJQACq2yQ1dl/OVY5sjf/FPn59xkkHFhMMuAvCGodNCBm PktW8Ms2Sw0oSsbeDth2su8JNV13SQJoKb9R2Mg= X-Google-Smtp-Source: AMrXdXtVScLglh0AJAAZrefEor8FTpbarQnSKKCQfgpuv9vDdBSoJVYiHs0dBsef6ADhG9FAQyJ4vuA0bohQjy6kD+4= X-Received: by 2002:a05:620a:1657:b0:709:1d0e:aee3 with SMTP id c23-20020a05620a165700b007091d0eaee3mr143054qko.587.1674239229612; Fri, 20 Jan 2023 10:27:09 -0800 (PST) MIME-Version: 1.0 References: <20230117195959.29768-1-nphamcs@gmail.com> <20230117195959.29768-3-nphamcs@gmail.com> In-Reply-To: From: Nhat Pham Date: Fri, 20 Jan 2023 10:26:54 -0800 Message-ID: Subject: Re: [PATCH v6 2/3] cachestat: implement cachestat syscall To: Brian Foster Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, willy@infradead.org, linux-api@vger.kernel.org, kernel-team@meta.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: B4FB340006 X-Stat-Signature: k755uxpy5sht331bmw1qjturrgwsywtk X-Rspam-User: X-HE-Tag: 1674239230-278444 X-HE-Meta: U2FsdGVkX19AecmjVku/nDzTMjcEm7s2e/kvTvdsVPh8O8vPs4F4JcPW/7qX8PXBcQ8FsVYasrkV1bGt7yybyDAtB9Ym3D3cai/y+xluo8pShU5Vs8qtKoNHqKspODFoLUhROB+XE7TKQKZwvoD5EotrkqYBGY+bV7Q2yBxw6nYj+4Bz+SuSmKN6EkqnNR62C5q6HFgnpjZXcBXGEYBZBNM9Yec56+JVI0OaCyZ4KFGTApg3sl0dTDVzu+3IyT/Xr18y4xrL+bHT1s5GlesUcQdOVSm1NK2S2KeoGkn9iEIqyqCmzP+vZfEoZgodQK/K2Fu5hRJ75j1JTWcpUSrnakHAUypASEs4vfEPcMckykgcRxSndw50vIMoMNTgoluMkVp1L5qxuOsKISctAQ2yHjKgz20+5AvrpQrusw7F5KRLXGMn0EOP93JsLMcDu7B0MPF8L/BE9VDaO32iB4cY5qbqFEA367t54T8gVutM82sf5k5XUkDZoRtWe4UKky239FcsxobGidoIjpR7QNc3sSNzwIBSewSyY1DHcq40sNLrBNwCcWZy5xNax9WN0SRpUwdBK+68zmiUpA5OkhrWeTaaUhQxbLjd/UaEZzKNbRkMFE1dTgA3tgCCvWmSIoIeM+/xyK+PNsi71NDKCUULqOgi2hrgt+xQqvDQPCAMJWsAY/VgD6H9ezroPOISDoxfSous3wlW6houYRpGnqpcEBKT5sVrOKZuVmj6rBcHRb9AS+X3dglc7Kgt/k3Z2tmGB6RJzBwXEXf89K3A3SN7y5/xRmn2F4aJ+ulQbYSdEQcKyiaCTdb+0egwLonnPBZD+B0Fx+hF9sfCyizC0hC2igORn/5ejY0ELLo5TTE+s41NwX3zgYgSCCMfC1lTF1/sruQxwUtHWnr0skVygzfGzupYtRlMkv1gn1/MV7pwYXIpzLpfPi8s+0feoWQ70A2EXAeOJi9q38nPWEgFGyN XBtlEjx0 ddPQxw83CeeN3nBir6WX57leWRJXzyOmPUoF/zxv2VdVA3a2fhY+hqIYsZnH4rWSyjjQf1xWbZ6Lfa301vIN7+BoDDSppEHNtCmC+mkQleBh5atWwoGNx64/yCXwMWoA48jqUaWeThpnjetnpCXtU+6C+DcEeIaeDeU1RsH/IVtGdQVAXJIyzoWTOVOeMy8dYFQ1jSlaxI6uRz5ozeg1Mjja5yrlm0f1bxqerzSRws1QOLpJaAzIG2r6KpSHRZ/fMRacq2dYH3+TmPC0HIB7b7X/71Sx0w93f60biS6vlCm8IBibBWCOGWsFzTXzUw0wCBJOxKeXvza5JyZSxDHGaMU68Wi7FY2jUJDDEr2IZeRfiu3YVMdHhxl64EHsVap0SkENH3cQXU2ZjmauMaEoZ0LAzuXPubp0+0sJK 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 Fri, Jan 20, 2023 at 6:35 AM Brian Foster wrote: > > On Tue, Jan 17, 2023 at 11:59:58AM -0800, Nhat Pham wrote: > > There is currently no good way to query the page cache state of large > > file sets and directory trees. There is mincore(), but it scales poorly: > > the kernel writes out a lot of bitmap data that userspace has to > > aggregate, when the user really doesn not care about per-page > > information in that case. The user also needs to mmap and unmap each > > file as it goes along, which can be quite slow as well. > > > > This patch implements a new syscall that queries cache state of a file > > and summarizes the number of cached pages, number of dirty pages, number > > of pages marked for writeback, number of (recently) evicted pages, etc. > > in a given range. > > > > NAME > > cachestat - query the page cache statistics of a file. > > > > SYNOPSIS > > #include > > > > struct cachestat { > > __u64 nr_cache; > > __u64 nr_dirty; > > __u64 nr_writeback; > > __u64 nr_evicted; > > __u64 nr_recently_evicted; > > }; > > > > int cachestat(unsigned int fd, off_t off, size_t len, > > unsigned int cstat_version, struct cachestat *cstat, > > unsigned int flags); > > > > DESCRIPTION > > cachestat() queries the number of cached pages, number of dirty > > pages, number of pages marked for writeback, number of evicted > > pages, number of recently evicted pages, in the bytes range given by > > `off` and `len`. > > > > An evicted page is a page that is previously in the page cache but > > has been evicted since. A page is recently evicted if its last > > eviction was recent enough that its reentry to the cache would > > indicate that it is actively being used by the system, and that > > there is memory pressure on the system. > > > > These values are returned in a cachestat struct, whose address is > > given by the `cstat` argument. > > > > The `off` and `len` arguments must be non-negative integers. If > > `len` > 0, the queried range is [`off`, `off` + `len`]. If `len` == > > 0, we will query in the range from `off` to the end of the file. > > > > `cstat_version` is an unsigned integer indicating the specific > > version of the cachestat struct. It must be at least 1, and does > > not exceed the latest version number (which is currently 1). For > > now, user should just pass 1. > > > > Still not sure about this vs. just requiring the structure size to match > (and maybe padding it), but perhaps linux-api can comment on the best > way to future proof. > > I'm not the person to ack a syscall regardless, but since I've had > various previous comments on this patch and no further issues stand out > to me: > > Reviewed-by: Brian Foster Thanks for the review and feedback, Brian! > > > The `flags` argument is unused for now, but is included for future > > extensibility. User should pass 0 (i.e no flag specified). > > > > RETURN VALUE > > On success, cachestat returns 0. On error, -1 is returned, and errno > > is set to indicate the error. > > > > ERRORS > > EFAULT cstat points to an invalid address. > > > > EINVAL invalid `cstat_version` or `flags` > > > > EBADF invalid file descriptor. > > > > Signed-off-by: Nhat Pham > > --- > > arch/alpha/kernel/syscalls/syscall.tbl | 1 + > > arch/arm/tools/syscall.tbl | 1 + > > arch/ia64/kernel/syscalls/syscall.tbl | 1 + > > arch/m68k/kernel/syscalls/syscall.tbl | 1 + > > arch/microblaze/kernel/syscalls/syscall.tbl | 1 + > > arch/parisc/kernel/syscalls/syscall.tbl | 1 + > > arch/powerpc/kernel/syscalls/syscall.tbl | 1 + > > arch/s390/kernel/syscalls/syscall.tbl | 1 + > > arch/sh/kernel/syscalls/syscall.tbl | 1 + > > arch/sparc/kernel/syscalls/syscall.tbl | 1 + > > arch/x86/entry/syscalls/syscall_32.tbl | 1 + > > arch/x86/entry/syscalls/syscall_64.tbl | 1 + > > arch/xtensa/kernel/syscalls/syscall.tbl | 1 + > > include/linux/fs.h | 3 + > > include/linux/syscalls.h | 4 + > > include/uapi/asm-generic/unistd.h | 5 +- > > include/uapi/linux/mman.h | 9 ++ > > init/Kconfig | 10 ++ > > kernel/sys_ni.c | 1 + > > mm/filemap.c | 154 ++++++++++++++++++++ > > 20 files changed, 198 insertions(+), 1 deletion(-) > > > > diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl > > index 8ebacf37a8cf..1f13995d00d7 100644 > > --- a/arch/alpha/kernel/syscalls/syscall.tbl > > +++ b/arch/alpha/kernel/syscalls/syscall.tbl > > @@ -490,3 +490,4 @@ > > 558 common process_mrelease sys_process_mrelease > > 559 common futex_waitv sys_futex_waitv > > 560 common set_mempolicy_home_node sys_ni_syscall > > +561 common cachestat sys_cachestat > > diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl > > index ac964612d8b0..8ebed8a13874 100644 > > --- a/arch/arm/tools/syscall.tbl > > +++ b/arch/arm/tools/syscall.tbl > > @@ -464,3 +464,4 @@ > > 448 common process_mrelease sys_process_mrelease > > 449 common futex_waitv sys_futex_waitv > > 450 common set_mempolicy_home_node sys_set_mempolicy_home_node > > +451 common cachestat sys_cachestat > > diff --git a/arch/ia64/kernel/syscalls/syscall.tbl b/arch/ia64/kernel/syscalls/syscall.tbl > > index 72c929d9902b..f8c74ffeeefb 100644 > > --- a/arch/ia64/kernel/syscalls/syscall.tbl > > +++ b/arch/ia64/kernel/syscalls/syscall.tbl > > @@ -371,3 +371,4 @@ > > 448 common process_mrelease sys_process_mrelease > > 449 common futex_waitv sys_futex_waitv > > 450 common set_mempolicy_home_node sys_set_mempolicy_home_node > > +451 common cachestat sys_cachestat > > diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl > > index b1f3940bc298..4f504783371f 100644 > > --- a/arch/m68k/kernel/syscalls/syscall.tbl > > +++ b/arch/m68k/kernel/syscalls/syscall.tbl > > @@ -450,3 +450,4 @@ > > 448 common process_mrelease sys_process_mrelease > > 449 common futex_waitv sys_futex_waitv > > 450 common set_mempolicy_home_node sys_set_mempolicy_home_node > > +451 common cachestat sys_cachestat > > diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl > > index 820145e47350..858d22bf275c 100644 > > --- a/arch/microblaze/kernel/syscalls/syscall.tbl > > +++ b/arch/microblaze/kernel/syscalls/syscall.tbl > > @@ -456,3 +456,4 @@ > > 448 common process_mrelease sys_process_mrelease > > 449 common futex_waitv sys_futex_waitv > > 450 common set_mempolicy_home_node sys_set_mempolicy_home_node > > +451 common cachestat sys_cachestat > > diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl > > index 8a99c998da9b..7c84a72306d1 100644 > > --- a/arch/parisc/kernel/syscalls/syscall.tbl > > +++ b/arch/parisc/kernel/syscalls/syscall.tbl > > @@ -448,3 +448,4 @@ > > 448 common process_mrelease sys_process_mrelease > > 449 common futex_waitv sys_futex_waitv > > 450 common set_mempolicy_home_node sys_set_mempolicy_home_node > > +451 common cachestat sys_cachestat > > diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl > > index 2bca64f96164..937460f0a8ec 100644 > > --- a/arch/powerpc/kernel/syscalls/syscall.tbl > > +++ b/arch/powerpc/kernel/syscalls/syscall.tbl > > @@ -530,3 +530,4 @@ > > 448 common process_mrelease sys_process_mrelease > > 449 common futex_waitv sys_futex_waitv > > 450 nospu set_mempolicy_home_node sys_set_mempolicy_home_node > > +451 common cachestat sys_cachestat > > diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl > > index 799147658dee..7df0329d46cb 100644 > > --- a/arch/s390/kernel/syscalls/syscall.tbl > > +++ b/arch/s390/kernel/syscalls/syscall.tbl > > @@ -453,3 +453,4 @@ > > 448 common process_mrelease sys_process_mrelease sys_process_mrelease > > 449 common futex_waitv sys_futex_waitv sys_futex_waitv > > 450 common set_mempolicy_home_node sys_set_mempolicy_home_node sys_set_mempolicy_home_node > > +451 common cachestat sys_cachestat sys_cachestat > > diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl > > index 2de85c977f54..97377e8c5025 100644 > > --- a/arch/sh/kernel/syscalls/syscall.tbl > > +++ b/arch/sh/kernel/syscalls/syscall.tbl > > @@ -453,3 +453,4 @@ > > 448 common process_mrelease sys_process_mrelease > > 449 common futex_waitv sys_futex_waitv > > 450 common set_mempolicy_home_node sys_set_mempolicy_home_node > > +451 common cachestat sys_cachestat > > diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl > > index 4398cc6fb68d..faa835f3c54a 100644 > > --- a/arch/sparc/kernel/syscalls/syscall.tbl > > +++ b/arch/sparc/kernel/syscalls/syscall.tbl > > @@ -496,3 +496,4 @@ > > 448 common process_mrelease sys_process_mrelease > > 449 common futex_waitv sys_futex_waitv > > 450 common set_mempolicy_home_node sys_set_mempolicy_home_node > > +451 common cachestat sys_cachestat > > diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl > > index 320480a8db4f..bc0a3c941b35 100644 > > --- a/arch/x86/entry/syscalls/syscall_32.tbl > > +++ b/arch/x86/entry/syscalls/syscall_32.tbl > > @@ -455,3 +455,4 @@ > > 448 i386 process_mrelease sys_process_mrelease > > 449 i386 futex_waitv sys_futex_waitv > > 450 i386 set_mempolicy_home_node sys_set_mempolicy_home_node > > +451 i386 cachestat sys_cachestat > > diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl > > index c84d12608cd2..227538b0ce80 100644 > > --- a/arch/x86/entry/syscalls/syscall_64.tbl > > +++ b/arch/x86/entry/syscalls/syscall_64.tbl > > @@ -372,6 +372,7 @@ > > 448 common process_mrelease sys_process_mrelease > > 449 common futex_waitv sys_futex_waitv > > 450 common set_mempolicy_home_node sys_set_mempolicy_home_node > > +451 common cachestat sys_cachestat > > > > # > > # Due to a historical design error, certain syscalls are numbered differently > > diff --git a/arch/xtensa/kernel/syscalls/syscall.tbl b/arch/xtensa/kernel/syscalls/syscall.tbl > > index 52c94ab5c205..2b69c3c035b6 100644 > > --- a/arch/xtensa/kernel/syscalls/syscall.tbl > > +++ b/arch/xtensa/kernel/syscalls/syscall.tbl > > @@ -421,3 +421,4 @@ > > 448 common process_mrelease sys_process_mrelease > > 449 common futex_waitv sys_futex_waitv > > 450 common set_mempolicy_home_node sys_set_mempolicy_home_node > > +451 common cachestat sys_cachestat > > diff --git a/include/linux/fs.h b/include/linux/fs.h > > index e654435f1651..83300f1491e7 100644 > > --- a/include/linux/fs.h > > +++ b/include/linux/fs.h > > @@ -75,6 +75,7 @@ struct fs_context; > > struct fs_parameter_spec; > > struct fileattr; > > struct iomap_ops; > > +struct cachestat; > > > > extern void __init inode_init(void); > > extern void __init inode_init_early(void); > > @@ -830,6 +831,8 @@ void filemap_invalidate_lock_two(struct address_space *mapping1, > > struct address_space *mapping2); > > void filemap_invalidate_unlock_two(struct address_space *mapping1, > > struct address_space *mapping2); > > +void filemap_cachestat(struct address_space *mapping, pgoff_t first_index, > > + pgoff_t last_index, struct cachestat *cs); > > > > > > /* > > diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h > > index a34b0f9a9972..d3fe6ba8eb38 100644 > > --- a/include/linux/syscalls.h > > +++ b/include/linux/syscalls.h > > @@ -72,6 +72,7 @@ struct open_how; > > struct mount_attr; > > struct landlock_ruleset_attr; > > enum landlock_rule_type; > > +struct cachestat; > > > > #include > > #include > > @@ -1056,6 +1057,9 @@ asmlinkage long sys_memfd_secret(unsigned int flags); > > asmlinkage long sys_set_mempolicy_home_node(unsigned long start, unsigned long len, > > unsigned long home_node, > > unsigned long flags); > > +asmlinkage long sys_cachestat(unsigned int fd, off_t off, size_t len, > > + unsigned int cstat_version, struct cachestat __user *cstat, > > + unsigned int flags); > > > > /* > > * Architecture-specific system calls > > diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h > > index 45fa180cc56a..cd639fae9086 100644 > > --- a/include/uapi/asm-generic/unistd.h > > +++ b/include/uapi/asm-generic/unistd.h > > @@ -886,8 +886,11 @@ __SYSCALL(__NR_futex_waitv, sys_futex_waitv) > > #define __NR_set_mempolicy_home_node 450 > > __SYSCALL(__NR_set_mempolicy_home_node, sys_set_mempolicy_home_node) > > > > +#define __NR_cachestat 451 > > +__SYSCALL(__NR_cachestat, sys_cachestat) > > + > > #undef __NR_syscalls > > -#define __NR_syscalls 451 > > +#define __NR_syscalls 452 > > > > /* > > * 32 bit systems traditionally used different > > diff --git a/include/uapi/linux/mman.h b/include/uapi/linux/mman.h > > index f55bc680b5b0..fe03ed0b7587 100644 > > --- a/include/uapi/linux/mman.h > > +++ b/include/uapi/linux/mman.h > > @@ -4,6 +4,7 @@ > > > > #include > > #include > > +#include > > > > #define MREMAP_MAYMOVE 1 > > #define MREMAP_FIXED 2 > > @@ -41,4 +42,12 @@ > > #define MAP_HUGE_2GB HUGETLB_FLAG_ENCODE_2GB > > #define MAP_HUGE_16GB HUGETLB_FLAG_ENCODE_16GB > > > > +struct cachestat { > > + __u64 nr_cache; > > + __u64 nr_dirty; > > + __u64 nr_writeback; > > + __u64 nr_evicted; > > + __u64 nr_recently_evicted; > > +}; > > + > > #endif /* _UAPI_LINUX_MMAN_H */ > > diff --git a/init/Kconfig b/init/Kconfig > > index 694f7c160c9c..da96ac29af1d 100644 > > --- a/init/Kconfig > > +++ b/init/Kconfig > > @@ -1798,6 +1798,16 @@ config RSEQ > > > > If unsure, say Y. > > > > +config CACHESTAT_SYSCALL > > + bool "Enable cachestat() system call" if EXPERT > > + default y > > + help > > + Enable the cachestat system call, which queries the page cache > > + statistics of a file (number of cached pages, dirty pages, > > + pages marked for writeback, (recently) evicted pages). > > + > > + If unsure say Y here. > > + > > config DEBUG_RSEQ > > default n > > bool "Enabled debugging of rseq() system call" if EXPERT > > diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c > > index 860b2dcf3ac4..04bfb1e4d377 100644 > > --- a/kernel/sys_ni.c > > +++ b/kernel/sys_ni.c > > @@ -299,6 +299,7 @@ COND_SYSCALL(set_mempolicy); > > COND_SYSCALL(migrate_pages); > > COND_SYSCALL(move_pages); > > COND_SYSCALL(set_mempolicy_home_node); > > +COND_SYSCALL(cachestat); > > > > COND_SYSCALL(perf_event_open); > > COND_SYSCALL(accept4); > > diff --git a/mm/filemap.c b/mm/filemap.c > > index 08341616ae7a..0305eaf5b3f5 100644 > > --- a/mm/filemap.c > > +++ b/mm/filemap.c > > @@ -22,6 +22,7 @@ > > #include > > #include > > #include > > +#include > > #include > > #include > > #include > > @@ -55,6 +56,13 @@ > > #include /* for try_to_free_buffers */ > > > > #include > > +#include > > + > > +#include "swap.h" > > + > > +#ifdef CONFIG_CACHESTAT_SYSCALL > > +#define LATEST_CACHESTAT_VERSION 1 > > +#endif > > > > /* > > * Shared mappings implemented 30.11.1994. It's not fully working yet, > > @@ -3949,3 +3957,149 @@ bool filemap_release_folio(struct folio *folio, gfp_t gfp) > > return try_to_free_buffers(folio); > > } > > EXPORT_SYMBOL(filemap_release_folio); > > + > > +/** > > + * filemap_cachestat() - compute the page cache statistics of a mapping > > + * @mapping: The mapping to compute the statistics for. > > + * @first_index: The starting page cache index. > > + * @last_index: The final page index (inclusive). > > + * @cs: the cachestat struct to write the result to. > > + * > > + * This will query the page cache statistics of a mapping in the > > + * page range of [first_index, last_index] (inclusive). The statistics > > + * queried include: number of dirty pages, number of pages marked for > > + * writeback, and the number of (recently) evicted pages. > > + */ > > +void filemap_cachestat(struct address_space *mapping, pgoff_t first_index, > > + pgoff_t last_index, struct cachestat *cs) > > +{ > > + XA_STATE(xas, &mapping->i_pages, first_index); > > + struct folio *folio; > > + > > + rcu_read_lock(); > > + xas_for_each(&xas, folio, last_index) { > > + unsigned long nr_pages; > > + pgoff_t folio_first_index, folio_last_index; > > + > > + if (xas_retry(&xas, folio)) > > + continue; > > + > > + nr_pages = folio_nr_pages(folio); > > + folio_first_index = folio_pgoff(folio); > > + folio_last_index = folio_first_index + nr_pages - 1; > > + > > + /* Folios might straddle the range boundaries, only count covered subpages */ > > + if (folio_first_index < first_index) > > + nr_pages -= first_index - folio_first_index; > > + > > + if (folio_last_index > last_index) > > + nr_pages -= folio_last_index - last_index; > > + > > + if (xa_is_value(folio)) { > > + /* page is evicted */ > > + void *shadow = (void *)folio; > > + bool workingset; /* not used */ > > + > > + cs->nr_evicted += nr_pages; > > + > > +#ifdef CONFIG_SWAP /* implies CONFIG_MMU */ > > + if (shmem_mapping(mapping)) { > > + /* shmem file - in swap cache */ > > + swp_entry_t swp = radix_to_swp_entry(folio); > > + > > + shadow = get_shadow_from_swap_cache(swp); > > + } > > +#endif > > + if (workingset_test_recent(shadow, true, &workingset)) > > + cs->nr_recently_evicted += nr_pages; > > + > > + goto resched; > > + } > > + > > + /* page is in cache */ > > + cs->nr_cache += nr_pages; > > + > > + if (folio_test_dirty(folio)) > > + cs->nr_dirty += nr_pages; > > + > > + if (folio_test_writeback(folio)) > > + cs->nr_writeback += nr_pages; > > + > > +resched: > > + if (need_resched()) { > > + xas_pause(&xas); > > + cond_resched_rcu(); > > + } > > + } > > + rcu_read_unlock(); > > +} > > +EXPORT_SYMBOL(filemap_cachestat); > > + > > +#ifdef CONFIG_CACHESTAT_SYSCALL > > +/* > > + * The cachestat(5) system call. > > + * > > + * cachestat() returns the page cache statistics of a file in the > > + * bytes range specified by `off` and `len`: number of cached pages, > > + * number of dirty pages, number of pages marked for writeback, > > + * number of evicted pages, and number of recently evicted pages. > > + * > > + * An evicted page is a page that is previously in the page cache > > + * but has been evicted since. A page is recently evicted if its last > > + * eviction was recent enough that its reentry to the cache would > > + * indicate that it is actively being used by the system, and that > > + * there is memory pressure on the system. > > + * > > + * `off` and `len` must be non-negative integers. If `len` > 0, > > + * the queried range is [`off`, `off` + `len`]. If `len` == 0, > > + * we will query in the range from `off` to the end of the file. > > + * > > + * `cstat_version` is an unsigned integer indicating the specific version > > + * of the cachestat struct. It must be at least 1, and does not exceed the > > + * latest version number (which is currently 1). For now, user should > > + * just pass 1. > > + * > > + * The `flags` argument is unused for now, but is included for future > > + * extensibility. User should pass 0 (i.e no flag specified). > > + * > > + * Because the status of a page can change after cachestat() checks it > > + * but before it returns to the application, the returned values may > > + * contain stale information. > > + * > > + * return values: > > + * zero - success > > + * -EFAULT - cstat points to an illegal address > > + * -EINVAL - invalid arguments > > + * -EBADF - invalid file descriptor > > + */ > > +SYSCALL_DEFINE6(cachestat, unsigned int, fd, off_t, off, size_t, len, > > + unsigned int, cstat_version, struct cachestat __user *, cstat, > > + unsigned int, flags) > > +{ > > + struct fd f = fdget(fd); > > + struct address_space *mapping; > > + struct cachestat cs; > > + pgoff_t first_index = off >> PAGE_SHIFT; > > + pgoff_t last_index = > > + len == 0 ? ULONG_MAX : (off + len - 1) >> PAGE_SHIFT; > > + > > + if (!f.file) > > + return -EBADF; > > + > > + if (off < 0 || flags != 0 || cstat_version < 1 || > > + cstat_version > LATEST_CACHESTAT_VERSION) { > > + fdput(f); > > + return -EINVAL; > > + } > > + > > + memset(&cs, 0, sizeof(struct cachestat)); > > + mapping = f.file->f_mapping; > > + filemap_cachestat(mapping, first_index, last_index, &cs); > > + fdput(f); > > + > > + if (copy_to_user(cstat, &cs, sizeof(struct cachestat))) > > + return -EFAULT; > > + > > + return 0; > > +} > > +#endif /* CONFIG_CACHESTAT_SYSCALL */ > > -- > > 2.30.2 > > >