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 B029DC83F22 for ; Tue, 15 Jul 2025 14:30:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 522B36B0098; Tue, 15 Jul 2025 10:30:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4AC7E6B0099; Tue, 15 Jul 2025 10:30:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3C2A46B009A; Tue, 15 Jul 2025 10:30:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 2DA2B6B0098 for ; Tue, 15 Jul 2025 10:30:46 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id E754F1A04FA for ; Tue, 15 Jul 2025 14:30:45 +0000 (UTC) X-FDA: 83666735250.01.1B97832 Received: from nyc.source.kernel.org (nyc.source.kernel.org [147.75.193.91]) by imf02.hostedemail.com (Postfix) with ESMTP id 412AF80017 for ; Tue, 15 Jul 2025 14:30:43 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=fFmIrfPm; spf=pass (imf02.hostedemail.com: domain of djwong@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=djwong@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1752589844; 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=Vvj6AP7csVKhYE6WjrjjcSJX0XHsge9yeLFU2mLqsvE=; b=EhvqUQKEqlW2neJNcaaAEF78KCWk3jlGS3zasz/YIOuXrw0vqy3TEAW8TX6WBPh/dAKBhw TAQ5Dz9rOUGRKkrLp41gQQHbWq/UIS7DtNTxj93S7s+vohPKYKDNbEwbHuYti3f+gB7wYQ 8/HVJEDj5cvs6YwqprRjgVwDAg/kD/g= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1752589844; a=rsa-sha256; cv=none; b=rcO62sEw/ESeWx3cUAhJrbLnS6TCSpM7UgSjteTmN+dIzJhfLEdipYb2wAgkbT6u7r3Pq9 tCZqwYwdaqsmXu+Y6MC9mLQ7buDZbaXH0DH6w0FafrhQq1Ftxw2wvIhzDLUs1AL9TecN+X ZV0vIOg38UMZm+g47A7vjd5Xmolm2A0= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=fFmIrfPm; spf=pass (imf02.hostedemail.com: domain of djwong@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=djwong@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id A87C5A5079C; Tue, 15 Jul 2025 14:30:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4B8C9C4CEE3; Tue, 15 Jul 2025 14:30:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752589842; bh=sV1OZP5WMBeyKyulfXGILmszhTuQ8xOGFvfPdffvOJ0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=fFmIrfPmJ7DAsHWOUFFVRGodoN8liMahk8iM7VXw3B4q+tfagwCYomKPsHLGjw8tC DMTG4TdnPN+ppLpbKF07Qqcq+jEEe3uPHEvKkL3+TTT4/f8mWadzhV+VildbgUx7/Y r5ugytVSnUVAezv+EsFWTy7W9gNy3LmqGBrmiybyLbpgpacc4jae2bwuTDpV2/i5/D gzmjgIR5tcH0Q2IzGdMIC4FC3mmHAxVzDhLxHmTiG0xRPu6Rmoq3FCxAIF/fjtDrzJ FQuN9LseWR1zN0mMvQ08GUIA45xgdup4iKjOVC9aOw5qqVoInuUrafaW1Qm1KziLpG aEpL7JDge/YGA== Date: Tue, 15 Jul 2025 07:30:41 -0700 From: "Darrick J. Wong" To: Brian Foster Cc: linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, hch@infradead.org, willy@infradead.org Subject: Re: [PATCH v3 7/7] xfs: error tag to force zeroing on debug kernels Message-ID: <20250715143041.GN2672029@frogsfrogsfrogs> References: <20250714204122.349582-1-bfoster@redhat.com> <20250714204122.349582-8-bfoster@redhat.com> <20250715052444.GP2672049@frogsfrogsfrogs> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 412AF80017 X-Stat-Signature: zy4mpisk6hbahbtm9fhxy4kfgazio3w6 X-Rspam-User: X-HE-Tag: 1752589843-864961 X-HE-Meta: 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 uqfSc//E MKPysVBl0MvfoRW1pKsX5r9W/Z9HNulMJdIA6Pl2irKdshDLiqRiVHBZKOZBWMPd6ESUl6ifK11LsspGh++3ofwvb0Tq7DwLPDGsTGMjly6Lhm/4C/WbzhhCGwCc7tPrJpqr86LhX0z3euxZvoEZsDYy9bbHIlIccQn3cuInUVJTfGC/JLvXrEIcYlqrwmLmbAZFpbUChzLcdTAS2ftUNxNrHgzVrHBEkp22Ln182uMIhZX6WGnhoB27ZnHBZLUO8X7Oe7OGvCqzC3GIa9fPsEC+pQNwqbJgbAgXFMwLuBBmg4csxN6Jz1ew3DVqzZlcgNrIx 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 Tue, Jul 15, 2025 at 08:39:03AM -0400, Brian Foster wrote: > On Mon, Jul 14, 2025 at 10:24:44PM -0700, Darrick J. Wong wrote: > > On Mon, Jul 14, 2025 at 04:41:22PM -0400, Brian Foster wrote: > > > iomap_zero_range() has to cover various corner cases that are > > > difficult to test on production kernels because it is used in fairly > > > limited use cases. For example, it is currently only used by XFS and > > > mostly only in partial block zeroing cases. > > > > > > While it's possible to test most of these functional cases, we can > > > provide more robust test coverage by co-opting fallocate zero range > > > to invoke zeroing of the entire range instead of the more efficient > > > block punch/allocate sequence. Add an errortag to occasionally > > > invoke forced zeroing. > > > > > > Signed-off-by: Brian Foster > > > Reviewed-by: Christoph Hellwig > > > --- > > > fs/xfs/libxfs/xfs_errortag.h | 4 +++- > > > fs/xfs/xfs_error.c | 3 +++ > > > fs/xfs/xfs_file.c | 26 ++++++++++++++++++++------ > > > 3 files changed, 26 insertions(+), 7 deletions(-) > > > > ... > > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > > > index 0b41b18debf3..c865f9555b77 100644 > > > --- a/fs/xfs/xfs_file.c > > > +++ b/fs/xfs/xfs_file.c > > > @@ -27,6 +27,8 @@ > > > #include "xfs_file.h" > > > #include "xfs_aops.h" > > > #include "xfs_zone_alloc.h" > > > +#include "xfs_error.h" > > > +#include "xfs_errortag.h" > > > > > > #include > > > #include > > > @@ -1269,13 +1271,25 @@ xfs_falloc_zero_range( > > > if (error) > > > return error; > > > > > > - error = xfs_free_file_space(XFS_I(inode), offset, len, ac); > > > - if (error) > > > - return error; > > > + /* > > > + * Zero range implements a full zeroing mechanism but is only used in > > > + * limited situations. It is more efficient to allocate unwritten > > > + * extents than to perform zeroing here, so use an errortag to randomly > > > + * force zeroing on DEBUG kernels for added test coverage. > > > + */ > > > + if (XFS_TEST_ERROR(false, XFS_I(inode)->i_mount, > > > + XFS_ERRTAG_FORCE_ZERO_RANGE)) { > > > + error = xfs_zero_range(XFS_I(inode), offset, len, ac, NULL); > > > > Isn't this basically the ultra slow version fallback version of > > FALLOC_FL_WRITE_ZEROES ? > > > > ~/linux$ git grep FALLOC_FL_WRITE_ZEROES > ~/linux$ > > IIRC write zeroes is intended to expose fast hardware (physical) zeroing > (i.e. zeroed written extents)..? If so, I suppose you could consider > this a fallback of sorts. I'm not sure what write zeroes is expected to > do in the unwritten extent case, whereas iomap zero range is happy to > skip those mappings unless they're already dirty in pagecache. Sorry, forgot that they weren't wiring anything up in xfs so it never showed up here: https://lore.kernel.org/linux-fsdevel/20250619111806.3546162-1-yi.zhang@huaweicloud.com/ Basically they want to avoid the unwritten extent conversion overhead by providing a way to preallocate written zeroed extents and sending magic commands to hardware that unmaps LBAs in such a way that rereads return zero. > Regardless, the purpose of this patch is not to add support for physical > zeroing, but rather to increase test coverage for the additional code on > debug kernels because the production use case tends to be more limited. > This could easily be moved/applied to write zeroes if it makes sense in > the future and test infra grows support for it. On second look, I don't think the new fallocate flag allows for letting the kernel do pagecache zeroing + flush. Admittedly that would be beside the point (and userspaces already do that anyway). Anyway enough mumbling from me, Reviewed-by: "Darrick J. Wong" --D > Brian > > > --D > > > > > + } else { > > > + error = xfs_free_file_space(XFS_I(inode), offset, len, ac); > > > + if (error) > > > + return error; > > > > > > - len = round_up(offset + len, blksize) - round_down(offset, blksize); > > > - offset = round_down(offset, blksize); > > > - error = xfs_alloc_file_space(XFS_I(inode), offset, len); > > > + len = round_up(offset + len, blksize) - > > > + round_down(offset, blksize); > > > + offset = round_down(offset, blksize); > > > + error = xfs_alloc_file_space(XFS_I(inode), offset, len); > > > + } > > > if (error) > > > return error; > > > return xfs_falloc_setsize(file, new_size); > > > -- > > > 2.50.0 > > > > > > > > > >