From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 D5F0F339A8 for ; Wed, 22 Oct 2025 11:17:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761131882; cv=none; b=qnvIZBh/vgG0aGFS50v2R6P81cGeVLPK9jJd+P+GTnDg8wk1IMMU+pwV7TZh9G49MOCzz1pwHiMd2w/OLT8ve3bwKnPKdpEFW95g0+c5DZC3xVqm82qsERZSrtrUmD2pA/fc90yUShLTDji3G5YsV2QkNUBqSEWmmzLXexfRRDU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761131882; c=relaxed/simple; bh=4HqLHGPLDY1DNEX4Ff2d4AQFWEOeQnQF1Yqsnf4KDbs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=L2cgKD/IbSR/Pt22sk3jK7w8A9VDc1RZ2gHjxGTWgc7TWcPArlCqpENHvFwrhgENB5J6jQzV0DK9oBX+sGTQz/z2g6aTQTm9douOx1AwNicaMAwspy2qQpnfnP2rjX6EvL/nLS8OAmx0zbL7lrcXN18mqwLudr6INrjVchasgfg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=d9dgilan; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="d9dgilan" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; 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=mCffRK2PUwrNqXHxelp3tc71Mmymc8MJR9C74MpMwyw=; b=d9dgilanaLealda45VKfrJubrB xGiwOPkrEp+dqX9iQtQyh3xK2fz6fxEz6RP0qsvDKef1EPOhNJHImfzJdFKzLFwPRc7EUXRbd8RrH HDdUoMkRc063Hw2weV42Xt5SeDgPmANwAAQbwNhmcMsI1TAuJj/2ithlVt3seaY8ote0ExBc8M84+ N+flF3lwQYC639hADSdRDutKfFLlBWMnpMfJ6/aEFjC49FqrjgExaFNXo727I2jDzICCOdjZ9VXV+ uzPYU9dphhrZIltg9bzoXpafyQq+T9L/pUAfac3wsYF4y/7a9lUWDS/vzkPFvuYyPte7uMe4+Ky+W PvxOMInA==; Received: from hch by bombadil.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1vBWqq-00000002cdk-1qe6; Wed, 22 Oct 2025 11:17:56 +0000 Date: Wed, 22 Oct 2025 04:17:56 -0700 From: Christoph Hellwig To: Jeff Layton Cc: Christoph Hellwig , Chuck Lever , NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey , linux-nfs@vger.kernel.org, Mike Snitzer Subject: Re: [PATCH v4 2/3] NFSD: Implement NFSD_IO_DIRECT for NFS WRITE Message-ID: References: <20251018005431.3403-1-cel@kernel.org> <20251018005431.3403-3-cel@kernel.org> <63a440d869e3f8a9ecf13537e2da6c6439933ed1.camel@kernel.org> Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <63a440d869e3f8a9ecf13537e2da6c6439933ed1.camel@kernel.org> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Wed, Oct 22, 2025 at 06:15:44AM -0400, Jeff Layton wrote: > Cache coherency. If the timestamps roll back, some clients may not > notice that data has changed after a write. > > It's not the end of the world -- non-evident timestamp changes were > typical prior to the multigrain timestamp patches going in, but it's > not ideal. Well, in that case nfsd_vfs_write needs to use IOCB_SYNC as well. And both that and this code need a big fat comment about it.