From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Williams Subject: Re: [PATCH v2 00/10] evacuate struct page from the block layer, introduce __pfn_t Date: Thu, 7 May 2015 09:03:27 -0700 Message-ID: References: <20150506200219.40425.74411.stgit@dwillia2-desk3.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: Linux Kernel Mailing List , Boaz Harrosh , Jan Kara , Mike Snitzer , Neil Brown , Benjamin Herrenschmidt , Dave Hansen , Heiko Carstens , Chris Mason , Paul Mackerras , "H. Peter Anvin" , Christoph Hellwig , Alasdair Kergon , "linux-nvdimm@lists.01.org" , Ingo Molnar , Mel Gorman , Matthew Wilcox , Ross Zwisler , Rik van Riel , Martin Schwidefsky , Jens Axboe , "Theodore Ts'o" , "Martin K. Petersen" , Juli To: Linus Torvalds Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Thu, May 7, 2015 at 8:58 AM, Linus Torvalds wrote: > On Thu, May 7, 2015 at 8:40 AM, Dan Williams wrote: >> >> blkdev_get(FMODE_EXCL) is the protection in this case. > > Ugh. That looks like a horrible nasty big hammer that will bite us > badly some day. Since you'd have to hold it for the whole IO. But I > guess it at least works. Oh no, that wouldn't be per-I/O that would be permanent at configuration set up time just like a raid member device. Something like: mdadm --create /dev/md0 --cache=/dev/pmem0p1 --storage=/dev/sda > Anyway, I did want to say that while I may not be convinced about the > approach, I think the patches themselves don't look horrible. I > actually like your "__pfn_t". So while I (very obviously) have some > doubts about this approach, it may be that the most convincing > argument is just in the code. Ok, I'll keep thinking about this and come back when we have a better story about passing mmap'd persistent memory around in userspace.