linux-kernel - Re: [PATCH v2 7/7] pmem, dax: have direct_access use _

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAPcyv4gHatJxtJ_Utc07L-EiX0f=SnkEoAVsB9PNDhtwmxrobQ@mail.gmail.com>
Date:	Sat, 15 Aug 2015 08:44:27 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Christoph Hellwig <hch@....de>
Cc:	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	Jonathan Corbet <corbet@....net>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Jens Axboe <axboe@...nel.dk>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux390@...ibm.com, Alexander Viro <viro@...iv.linux.org.uk>,
	Matthew Wilcox <willy@...ux.intel.com>,
	Jeff Layton <jlayton@...marydata.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Omar Sandoval <osandov@...ndov.com>,
	Boaz Harrosh <boaz@...xistor.com>,
	Miklos Szeredi <mszeredi@...e.cz>, Jan Kara <jack@...e.cz>,
	Wolfram Sang <wsa@...-dreams.de>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	Gerald Schaefer <gerald.schaefer@...ibm.com>,
	Ameen Ali <ameenali023@...il.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Sagi Grimberg <sagig@...lanox.com>,
	Mike Snitzer <snitzer@...hat.com>, Tejun Heo <tj@...nel.org>,
	Shaohua Li <shli@...com>, Ming Lei <ming.lei@...onical.com>,
	linux-doc@...r.kernel.org,
	linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
	linux-s390@...r.kernel.org,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Dave Chinner <david@...morbit.com>
Subject: Re: [PATCH v2 7/7] pmem, dax: have direct_access use __pmem annotation

On Sat, Aug 15, 2015 at 2:19 AM, Christoph Hellwig <hch@....de> wrote:
> On Thu, Aug 13, 2015 at 10:51:11AM -0600, Ross Zwisler wrote:
>> Update the annotation for the kaddr pointer returned by direct_access()
>> so that it is a __pmem pointer.  This is consistent with the PMEM driver
>> and with how this direct_access() pointer is used in the DAX code.
>
> IFF we stick to the __pmem annotations this looks good.
>
> That beeing said I start to really dislike them.  We don't special
> accesors to read/write from pmem, we just need to explicitly commit
> it if we want to make it persistent.  So I really don't see the need
> to treat it special and require all the force casts to and from the
> attribute.

I'm not going to put up much of a fight if it's really getting in the way....

That said, while we don't need special accessors we do need guarantees
that anything that has written to a persistent memory address has done
so in a way that wmb_pmem() is able to flush it.  It's more of a "I've
audited this code path for wmb_pmem() compatibility so use this api to
write to pmem."

Perhaps a better way to statically check for missed flushes might be
to have acquire_pmem_for_write() + release() annotations and the final
release does a wmb_pmem(), but as far as I can tell the sparse
acquire/release annotations don't stack.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/