From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f51.google.com (mail-wm0-f51.google.com [74.125.82.51]) by kanga.kvack.org (Postfix) with ESMTP id B94836B0257 for ; Fri, 13 Nov 2015 19:20:41 -0500 (EST) Received: by wmvv187 with SMTP id v187so104525935wmv.1 for ; Fri, 13 Nov 2015 16:20:41 -0800 (PST) Received: from mail-wm0-x22a.google.com (mail-wm0-x22a.google.com. [2a00:1450:400c:c09::22a]) by mx.google.com with ESMTPS id u4si29524977wjq.30.2015.11.13.16.20.40 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 13 Nov 2015 16:20:40 -0800 (PST) Received: by wmww144 with SMTP id w144so48537321wmw.1 for ; Fri, 13 Nov 2015 16:20:40 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <1447459610-14259-4-git-send-email-ross.zwisler@linux.intel.com> References: <1447459610-14259-1-git-send-email-ross.zwisler@linux.intel.com> <1447459610-14259-4-git-send-email-ross.zwisler@linux.intel.com> Date: Fri, 13 Nov 2015 16:20:39 -0800 Message-ID: Subject: Re: [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling From: Dan Williams Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Ross Zwisler Cc: "linux-kernel@vger.kernel.org" , "H. Peter Anvin" , "J. Bruce Fields" , Theodore Ts'o , Alexander Viro , Andreas Dilger , Dave Chinner , Ingo Molnar , Jan Kara , Jeff Layton , Matthew Wilcox , Thomas Gleixner , linux-ext4@vger.kernel.org, linux-fsdevel , Linux MM , "linux-nvdimm@lists.01.org" , X86 ML , xfs@oss.sgi.com, Andrew Morton , Matthew Wilcox , Dave Hansen On Fri, Nov 13, 2015 at 4:06 PM, Ross Zwisler wrote: > Currently the PMEM driver doesn't accept REQ_FLUSH or REQ_FUA bios. These > are sent down via blkdev_issue_flush() in response to a fsync() or msync() > and are used by filesystems to order their metadata, among other things. > > When we get an msync() or fsync() it is the responsibility of the DAX code > to flush all dirty pages to media. The PMEM driver then just has issue a > wmb_pmem() in response to the REQ_FLUSH to ensure that before we return all > the flushed data has been durably stored on the media. > > Signed-off-by: Ross Zwisler Hmm, I'm not seeing why we need this patch. If the actual flushing of the cache is done by the core why does the driver need support REQ_FLUSH? Especially since it's just a couple instructions. REQ_FUA only makes sense if individual writes can bypass the "drive" cache, but no I/O submitted to the driver proper is ever cached we always flush it through to media. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org