From patchwork Thu Aug 26 13:55:02 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christoph Hellwig X-Patchwork-Id: 12459919 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 919B13FC0 for ; Thu, 26 Aug 2021 13:57:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description; bh=gkQP9uUaGfS5wkgQnCeApEQiDrXMIWuavFG8HhovtVM=; b=YELdD3RiXQmIZRDAWJG6StBpiW 8V8yP1Pv4+xmDpG2E0lNxgeQVUcF8r1bZUK3PKxOMkl+JoG7pViWpazRfEWyh1Dd8Alcl5lu3eFxK omCf4HTx5zmokNJEEJBiMLTzY8S1h7HjYcGxDlURxr9dXmrwM76ga0XO064FxQsJZg1uU858pPrkf ZKFur1VoreyfW3nGnHuCvCxW3SXVmbRiDrHrjwNUZUsrDRVsklWvmaUI/OuChxfvRbQ/xrsohUEB4 eHoSSlPMjpIjQZDE6kAzD+aUk2EdEvW8xW31RVMNr6h3Z6NXZvlzgCfsP1HeksIyxiUTwnEKjHJ0i Owm2hheg==; Received: from [2001:4bb8:193:fd10:d9d9:6c15:481b:99c4] (helo=localhost) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mJFra-00DM3M-3A; Thu, 26 Aug 2021 13:56:26 +0000 From: Christoph Hellwig To: Dan Williams , Vishal Verma , Dave Jiang Cc: Mike Snitzer , Matthew Wilcox , linux-xfs@vger.kernel.org, nvdimm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org Subject: [PATCH 1/9] fsdax: improve the FS_DAX Kconfig description and help text Date: Thu, 26 Aug 2021 15:55:02 +0200 Message-Id: <20210826135510.6293-2-hch@lst.de> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210826135510.6293-1-hch@lst.de> References: <20210826135510.6293-1-hch@lst.de> Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Rename the main option text to clarify it is for file system access, and add a bit of text that explains how to actually switch a nvdimm to a fsdax capable state. Signed-off-by: Christoph Hellwig --- fs/Kconfig | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/fs/Kconfig b/fs/Kconfig index a7749c126b8e..bd21535a7620 100644 --- a/fs/Kconfig +++ b/fs/Kconfig @@ -43,7 +43,7 @@ source "fs/f2fs/Kconfig" source "fs/zonefs/Kconfig" config FS_DAX - bool "Direct Access (DAX) support" + bool "File system based Direct Access (DAX) support" depends on MMU depends on !(ARM || MIPS || SPARC) select DEV_PAGEMAP_OPS if (ZONE_DEVICE && !FS_DAX_LIMITED) @@ -53,8 +53,23 @@ config FS_DAX Direct Access (DAX) can be used on memory-backed block devices. If the block device supports DAX and the filesystem supports DAX, then you can avoid using the pagecache to buffer I/Os. Turning - on this option will compile in support for DAX; you will need to - mount the filesystem using the -o dax option. + on this option will compile in support for DAX. + + For a DAX device to support file system access it needs to have + struct pages. For the nfit based NVDIMMs this can be enabled + using the ndctl utility: + + # ndctl create-namespace --force --reconfig=namespace0.0 \ + --mode=fsdax --map=mem + + See the 'create-namespace' man page for details on the overhead of + --map=mem: + https://docs.pmem.io/ndctl-user-guide/ndctl-man-pages/ndctl-create-namespace + + For ndctl to work CONFIG_DEV_DAX needs to be enabled as well. For most + file systems DAX support needs to be manually enabled globally or + per-inode using a mount option as well. See the file documentation in + Documentation/filesystems/dax.rst for details. If you do not have a block device that is capable of using this, or if unsure, say N. Saying Y will increase the size of the kernel