From patchwork Fri Dec 16 19:21:48 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nhat Pham X-Patchwork-Id: 13075339 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 8DB3AC4167B for ; Fri, 16 Dec 2022 19:21:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2CD6E8E0007; Fri, 16 Dec 2022 14:21:58 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2A63C8E0001; Fri, 16 Dec 2022 14:21:58 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 00D318E0007; Fri, 16 Dec 2022 14:21:57 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id E3BA98E0001 for ; Fri, 16 Dec 2022 14:21:57 -0500 (EST) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id AC2C9A1233 for ; Fri, 16 Dec 2022 19:21:57 +0000 (UTC) X-FDA: 80249139474.21.1D3E122 Received: from mail-pj1-f43.google.com (mail-pj1-f43.google.com [209.85.216.43]) by imf29.hostedemail.com (Postfix) with ESMTP id D9E53120006 for ; Fri, 16 Dec 2022 19:21:55 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=XyvoQwzM; spf=pass (imf29.hostedemail.com: domain of nphamcs@gmail.com designates 209.85.216.43 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=1671218516; a=rsa-sha256; cv=none; b=z742+czWik8Qe3AhNEqgRVlyx5TFE5SH2siU7sT/EcmzVYjbGtBvWQsynwhK/5b1Me7233 JZlB1ULaIza4KtJhg1dJHjenJILgkq95is7Iaecghdz4xLP9L/oqjZo/xYsj9rV1+AsVH1 JqVpYrvINm6F3p9daaBN7wyzRkMEfk0= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=XyvoQwzM; spf=pass (imf29.hostedemail.com: domain of nphamcs@gmail.com designates 209.85.216.43 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=1671218516; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=mcfj7//KZGx3L4vs1asXbZHiEbvSE2W37vabxM0hoJ8=; b=stUgltcBayVK1NUNSIwDOBkIpBbIVbjendcRv5W5agkDDZSH8Z6S1yYzXZFQRRzMZE9tAM CQbV3CEB/V/rDKlQjUK7SyE6sWdy1/DSJPtyUVZNlCTKodk7fmsiXd+zazwiwAT8Bp2eRV bW9sSKl+fqCSIbLrxKWNqbawkKSZWMA= Received: by mail-pj1-f43.google.com with SMTP id z8-20020a17090abd8800b00219ed30ce47so7066589pjr.3 for ; Fri, 16 Dec 2022 11:21:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=mcfj7//KZGx3L4vs1asXbZHiEbvSE2W37vabxM0hoJ8=; b=XyvoQwzMgd30oKLXbNCSHtBaFKuZiO62uBdvtZ0V+ri6ypZX1wYUEYC6CfR9jnAIUZ oXovRbwVtPxgB8xGuhGfdOAADmxaUqygXmHamXKxCPOW7eJGEjBIOevihiXmmdOUuJyS SgBWKEpogOMb60EJL+GTwP/hvCjtOhvPAz2zhaG85oCoYeHRVFzrS80EM1bztbhLchFv P/XiJqCIg7w3Rlhu8FFDAxviL1e5ahSEpx7hnFilhVJCF0KDDYz1TzJV0glGWt7CDykz uSSwLQYRrFFBnKL4sTFD6V/4jx2878YW6rR4B+iHRm431MXqy3QZIxSiDTMMv3qrp7QO /ehA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=mcfj7//KZGx3L4vs1asXbZHiEbvSE2W37vabxM0hoJ8=; b=JIfiNHZGtW85gmGZmBnuHUa0ygQ0kcDaAMtUY11sdrlAQ4liMfw3eIW0spqhLylVOn P1eEVovvYVLJ2vk3HmmO5DDWxN/nFTvIRe3tbctcwHdQprPN9tYWzs/YE8yGJsbDEe9U sDSLA8iJecpQ3Mn4+94/M4FxFl091V+DfP8c4tV+sH3tfcjjxe7hFPoWzgZsec47nYnd Nsk9yVm07Nz6T2G/watIW0PXXchIQ62PKI770PUnZJwST9I58M8mNqzw9aMzvaZuRCwk qwmNRe+brAlpGZTfc++W3+su1GWc4f4GdBRBN1vp5kGB8an12HqHhxrKT6IoTWS2izGx kL3A== X-Gm-Message-State: ANoB5pnA6sWMghFTp+10a31e7kSYwrABv97mN0wBwix6dgB/cJuVkDr6 U2WgbaIQW8jyQNhgHQ0f4bDc8Rr+Jc4= X-Google-Smtp-Source: AA0mqf4bcRH4p+Q+rVHAlrlNkaHfUfl6OGuj5i02Ow7BCv6Ht00/D1exiyR13xkrkMCQSdy3+eT0/g== X-Received: by 2002:a17:902:8548:b0:18c:fd25:a934 with SMTP id d8-20020a170902854800b0018cfd25a934mr30262434plo.61.1671218514611; Fri, 16 Dec 2022 11:21:54 -0800 (PST) Received: from localhost (fwdproxy-prn-118.fbsv.net. [2a03:2880:ff:76::face:b00c]) by smtp.gmail.com with ESMTPSA id ja5-20020a170902efc500b001873aa85e1fsm1953676plb.305.2022.12.16.11.21.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Dec 2022 11:21:54 -0800 (PST) From: Nhat Pham To: akpm@linux-foundation.org Cc: hannes@cmpxchg.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, bfoster@redhat.com, willy@infradead.org, kernel-team@meta.com Subject: [PATCH v4 3/4] cachestat: implement cachestat syscall Date: Fri, 16 Dec 2022 11:21:48 -0800 Message-Id: <20221216192149.3902877-4-nphamcs@gmail.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20221216192149.3902877-1-nphamcs@gmail.com> References: <20221216192149.3902877-1-nphamcs@gmail.com> MIME-Version: 1.0 X-Rspam-User: X-Rspamd-Queue-Id: D9E53120006 X-Rspamd-Server: rspam01 X-Stat-Signature: d8tif3fys9ki11kgmt6hpwg878bt5xqq X-HE-Tag: 1671218515-29732 X-HE-Meta: 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 r1cW7vCe BSTVyaccTUAMtR7fWk3EMNFbLtDf7SSoHhgPS8skHVpbqkh8ss4EnwxJ1niUE2ZLAOLnnUmXOO4gr5vwO6lDvsbd4NW7rm1bxkvKkjgkK1BlaAm/QBMlFChXyXWxQG1F29gum 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: Implement 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 status 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, size_t cstat_size, 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 (recently) evicted pages, in the bytes range given by `off` and `len`. 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_size` allows users to obtain partial results. The syscall will copy the first `csstat_size` bytes to the specified userspace memory. `cstat_size` must be a non-negative value that is no larger than the current size of the cachestat struct. 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_size` 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 | 3 + include/uapi/asm-generic/unistd.h | 5 +- include/uapi/linux/mman.h | 9 ++ init/Kconfig | 10 ++ kernel/sys_ni.c | 1 + mm/filemap.c | 137 ++++++++++++++++++++ 20 files changed, 180 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..8902799121c9 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -46,6 +46,7 @@ #include #include +#include struct backing_dev_info; struct bdi_writeback; @@ -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..50f8c6999d99 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 +1057,8 @@ 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, + size_t cstat_size, 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..ecc4f781dd6c 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1798,6 +1798,16 @@ config RSEQ If unsure, say Y. +config CACHESTAT + 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..29ffb906caa4 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -22,6 +22,7 @@ #include #include #include +#include #include #include #include @@ -55,6 +56,9 @@ #include /* for try_to_free_buffers */ #include +#include + +#include "swap.h" /* * Shared mappings implemented 30.11.1994. It's not fully working yet, @@ -3949,3 +3953,136 @@ bool filemap_release_folio(struct folio *folio, gfp_t gfp) return try_to_free_buffers(folio); } EXPORT_SYMBOL(filemap_release_folio); + +#ifdef CONFIG_CACHESTAT +/** + * 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; + + continue; + } + + /* 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; + } + rcu_read_unlock(); +} +EXPORT_SYMBOL(filemap_cachestat); + +/* + * The cachestat(5) system call. + * + * cachestat() returns the page cache statistics of a file in the + * bytes specified by `off` and `len`: number of cached pages, + * number of dirty pages, number of pages marked for writeback, + * number of (recently) evicted pages. + * + * `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_size` allows users to obtain partial results. The syscall + * will copy the first `csstat_size` bytes to the specified userspace + * memory. It also makes the cachestat struct extensible - new fields + * can be added in the future without breaking existing usage. + * `cstat_size` must be a non-negative value that is no larger than + * the current size of the cachestat struct. + * + * 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, + size_t, cstat_size, 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 (off < 0 || cstat_size > sizeof(struct cachestat) || flags != 0) + return -EINVAL; + + if (!f.file) + return -EBADF; + + 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, cstat_size)) + return -EFAULT; + + return 0; +} +#endif /* CONFIG_CACHESTAT */