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 CE5F3D33986 for ; Mon, 28 Oct 2024 14:04:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 664E16B008C; Mon, 28 Oct 2024 10:04:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 614216B0095; Mon, 28 Oct 2024 10:04:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 503106B0096; Mon, 28 Oct 2024 10:04:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 369BF6B008C for ; Mon, 28 Oct 2024 10:04:18 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id C0374A04C9 for ; Mon, 28 Oct 2024 14:04:17 +0000 (UTC) X-FDA: 82723179882.23.1ECB576 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf02.hostedemail.com (Postfix) with ESMTP id 0D98880020 for ; Mon, 28 Oct 2024 14:03:30 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=lxCZvALT; spf=none (imf02.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1730124099; 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=Sq3n4ZBLfS4RB/WURRVHc91SFe8DIKYxMpdakJNvepo=; b=a9CFuz3xvK5kCUdAbiwZBNO7vFVzi85srpHl7JWq/U/cQ40p4Uk984K6Jcr/3eoDF6FPC6 L8xDhzijGIwrOqZWaCpbs2CUwe+JyRFHgkBuNYafMat8JCysyPxExAXs+RuLc7SUeBY/GF e7ikGw4CoOFY5FX2Gbn1oj8rNAlz0ss= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1730124099; a=rsa-sha256; cv=none; b=KVSBBNtPSfy5hhf3+RespA2pa4uwGPJvW002auyW7LmgRezCs97w39jAB8GdMjqdpgai/2 TNtaRa7lHPonszRQ9QAFAt+uuwHS3DpNtw905Ww/dRUz0dAhbAi74MqC0pMW65zyfZaPl1 1q4aBRewsxXKHfPLSzRQuYC8J5wF0NY= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=lxCZvALT; spf=none (imf02.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Sq3n4ZBLfS4RB/WURRVHc91SFe8DIKYxMpdakJNvepo=; b=lxCZvALTryteSo3HihrYgynWDg Oafy7lbdM82qIS7vgdx0ipIdHZYfWkDki/wfqkX/v0pukUrMEgZA2OKbWwRiNNJYskP71Z3OvRgor wbVHDDcOWeLect7PRt27wSywAYt6K4YtXJa58xRao2Y7yJP6dKpej7uBUQyAA+MXJeOjk9BNTLVwy ANtmbqTMoq0Sc3klJWQSkhcx2f7F8J4ePu0a7EJZIhzjAhsMZ0CUpfjq8SoUq0UI6xwrLMmvpT6fZ 73KvxEkHaSKPWo+wSb/gRnii7xqzHolW0ZyTpMJa4Gd59Kyb505dhSiRRUG09ut1nhD+2XPJ6ndKl iq8hLzKA==; Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1t5QLm-00000008aT6-2tF9; Mon, 28 Oct 2024 14:04:06 +0000 Date: Mon, 28 Oct 2024 14:04:06 +0000 From: Matthew Wilcox To: Hugh Dickins Cc: Alexander Viro , Andrew Morton , Christian Brauner , Christoph Hellwig , Kent Overstreet , "Darrick J. Wong" , Thomas Gleixner , Peter Zijlstra , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] iov_iter: fix copy_page_from_iter_atomic() if KMAP_LOCAL_FORCE_MAP Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 0D98880020 X-Stat-Signature: fug54g5cgppysufcej4onb5e1rbdf3ea X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1730124210-363220 X-HE-Meta: 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 iqh7oljD 0j46x4gv38c0W4pG5GHSc11RKZTw+W0M3vgKG/sQXrwtfBn/UjEyW9zFfD+O4jZnNFbJHMjGpR7LgPRGS72j3U5vVMe+N6Rfr5B+x9ArRYg51eSEOUhbfolkyA9i/OWntBC0Cfmya5mRysQUk/5XdSRsmGqKMssecSSi25KUqPyEwnSlz4j3/l4ES4HKi7lR37V2C7YBQqJrAySOF9+mv+syo6UcUbanFHi6enGdP9F+m73MZZfwZq+G4UIUkFlcqLKOTnSYleUZjjaqzV3vIru3PKQ== 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: List-Subscribe: List-Unsubscribe: On Sun, Oct 27, 2024 at 03:23:23PM -0700, Hugh Dickins wrote: > generic/077 on x86_32 CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP=y with highmem, > on huge=always tmpfs, issues a warning and then hangs (interruptibly): > +++ b/lib/iov_iter.c > @@ -461,6 +461,8 @@ size_t copy_page_from_iter_atomic(struct page *page, size_t offset, > size_t bytes, struct iov_iter *i) > { > size_t n, copied = 0; > + bool uses_kmap = IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) || > + PageHighMem(page); > > if (!page_copy_sane(page, offset, bytes)) > return 0; > @@ -471,7 +473,7 @@ size_t copy_page_from_iter_atomic(struct page *page, size_t offset, > char *p; > > n = bytes - copied; > - if (PageHighMem(page)) { > + if (uses_kmap) { > page += offset / PAGE_SIZE; > offset %= PAGE_SIZE; > n = min_t(size_t, n, PAGE_SIZE - offset); Urgh. I've done this same optimisation elsewhere. memcpy_from_folio: if (folio_test_highmem(folio) && chunk > PAGE_SIZE - offset_in_page(offset)) chunk = PAGE_SIZE - offset_in_page(offset); also memcpy_to_folio(), folio_zero_tail(), folio_fill_tail(), memcpy_from_file_folio() I think that means we need a new predicate. I don't have a good name yet. folio_kmap_can_access_multiple_pages() is a bit too wordy. Anyone think of a good one?