Re: [PATCH v8 3/7] mm, devm_memremap_pages: Fix shutdown handling

From: Logan Gunthorpe <logang@deltatee.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
	stable <stable@vger.kernel.org>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Christoph Hellwig" <hch@lst.de>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	"Linux MM" <linux-mm@kvack.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"Maling list - DRI developers" <dri-devel@lists.freedesktop.org>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Stephen Bates" <sbates@raithlin.com>
Subject: Re: [PATCH v8 3/7] mm, devm_memremap_pages: Fix shutdown handling
Date: Fri, 30 Nov 2018 15:34:07 -0700	[thread overview]
Message-ID: <b55bf34b-9ff2-2c28-afdb-08e20b9ba84e@deltatee.com> (raw)
In-Reply-To: <CAPcyv4iVCMo29SWM2jhnNTZ5ugYaqjeW_LKe9O2YmeNohwQG3A@mail.gmail.com>

On 2018-11-30 3:28 p.m., Dan Williams wrote:
> On Fri, Nov 30, 2018 at 2:19 PM Logan Gunthorpe <logang@deltatee.com> wrote:
>>
>> Hey,
>>
>> On 2018-11-29 11:51 a.m., Dan Williams wrote:
>>> Got it, let me see how bad moving arch_remove_memory() turns out,
>>> sounds like a decent approach to coordinate multiple users of a single
>>> ref.
>>
>> I've put together a patch set[1] that fixes all the users of
>> devm_memremap_pages() without moving arch_remove_memory(). It's pretty
>> clean except for the p2pdma case which is fairly tricky but I don't
>> think there's an easy way around that.
> 
> The solution I'm trying is to introduce a devm_memremap_pages_remove()
> that each user can call after they have called percpu_ref_exit(), it's
> just crashing for me currently...

Ok, that's probably less of a clean up for other users, but sounds like
it would be less tricky for p2pdma. I'd have to create a list of all
pgmaps, but that's not so hard and doesn't create any nasty races to
consider like my current solution.

>> If you come up with a better solution that's great, otherwise let me
>> know and I'll do some clean up and more testing and send this set to the
>> lists. Though, we might need to wait for your patch to land before we
>> can properly send the fix to it (the first patch in my series)...
> 
> I'd say go ahead and send it. We can fix p2pdma as a follow-on. Send
> it to Andrew as a patch relative to the current -next tree.

Ok, though, how do I reference the current patch in Andrew's tree? Or
does it matter?

Logan