From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7283B394EBA; Tue, 4 Aug 2026 18:57:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785869823; cv=none; b=eF7siKxBvALoDX1/CkhHSq1TsWCwHZKY8Y2wDyJGrHv3vHtsffZu+9kbneXpwY/eJhEYQpYw43XRQTPL2fENqwOsemZMiRSo8Q6bCbwvza3eKEeYNGKfyd1H6/z7yQWqhg/h0ueFST2mkq54r21H2UX3q3E0s2qlwucwBxHhS98= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785869823; c=relaxed/simple; bh=LHSZsrwWDBaz8zP92XmnGn8A5ADmrhSn0wLK+F/uS0I=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=b9YmQsrZEJJdskLOWI/x2t15agmwDRDXyK6loL8lq3h/QoiR3pk1VzdqUMotWa5qQIlG/ZpzAiEaa8cigu0gNiVv3NEro7AQ6Rodmm1u5WSidRrjtQs1KfOIlV53eJNNQvxIcVZNQ8PQ/EOPegyIJTCKjmsSDCgcIbqta8VokOY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bTBfxSVx; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bTBfxSVx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8DD491F000E9; Tue, 4 Aug 2026 18:57:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785869822; bh=uhwOVppSRbXMKKCTiEx73huPloNqZB23NIsD+UJKgS4=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=bTBfxSVxHNSSiTMy+XjmV9JBgdMXcWkEebXrsyCKAkbJNr8hufQTkhA6FGGPT2uzo iZYvyjT3K2TFnrn3clOypQEb4II+OrC8nJvvox9oLcUqGhJfIEUvW/+P+vFJZ6xMK+ gFxLsdaYceaMJzuiWoV+70e6FHCwN8TL33ngig3OwaoZEawbkDLSE5snIUptVic/Bt GCABBSFvEra2BcEDwDwK5/5LASdWsesh/FNkh9B8Hgdnf1J+VnTqbAtpf9Gylcsmct dgSVt7rxeCQPVfNr6yaiMTOj3KxtKb9jzMjxe54cdXAPZAcE7PQoB8FxDk+43jgl3B 5evwlyUajkuCg== Date: Tue, 4 Aug 2026 18:57:00 +0000 From: Eric Biggers To: Christoph Hellwig Cc: Andrey Albershteyn , linux-xfs@vger.kernel.org, fsverity@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-btrfs@vger.kernel.org, djwong@kernel.org Subject: Re: [PATCH v14 05/21] fsverity: improve flushing performance of fsverity_fill_zerohash Message-ID: <20260804185700.GE2904385@google.com> References: <20260803200820.393203-1-aalbersh@kernel.org> <20260803200820.393203-6-aalbersh@kernel.org> <20260804174223.GB14046@lst.de> <20260804183752.GC2904385@google.com> Precedence: bulk X-Mailing-List: fsverity@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260804183752.GC2904385@google.com> On Tue, Aug 04, 2026 at 06:37:52PM +0000, Eric Biggers wrote: > On Tue, Aug 04, 2026 at 07:42:23PM +0200, Christoph Hellwig wrote: > > On Mon, Aug 03, 2026 at 10:07:55PM +0200, Andrey Albershteyn wrote: > > > The current version calls flush_dcache_folio(), in memcpy_to_folio(), to > > > flush whole folio on every digest (which is 128 for 4k) on the HIGHMEM > > > systems. Open code folio mapping and flushing to copy all digests at > > > once. > > > > This looks correct, although to me optimizing for this feels like > > premature optimizations not worth the ugly code unless we have numbers > > to justify it. > > > > If Eric wants it: > > > > Reviewed-by: Christoph Hellwig > > > > > + if (folio_test_partial_kmap(folio) && > > > + off > PAGE_SIZE - offset_in_page(offset)) > > > + off = PAGE_SIZE - offset_in_page(offset); > > > + for (; to < (vaddr + off); to += vi->tree_params.digest_size) > > > > Style nitpick: no need for braces when comparing with simple > > integer arithmetics like this. > > > > > + for (off = offset; off < (offset + len); > > > > Same here. > > Well I didn't ask for it per se, but I pointed it out and asked whether > anyone will care about the combination of XFS && FS_VERITY && HIGHMEM. > Based on Darrick's email it seems the answer may be no? > > If it's kept as-is, adding a comment mentioning that it doesn't need to > be optimized for HIGHMEM would help preempt any questions about it. Note that the explanation in the commit message seems to be confusing people as well. It only mentions flush_dcache_folio(), when the actual performance problem on HIGHMEM would be the mapping and unmapping. - Eric