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From: Dan Williams <dan.j.williams@intel.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jane Chu <jane.chu@oracle.com>,
	"david@fromorbit.com" <david@fromorbit.com>,
	 "djwong@kernel.org" <djwong@kernel.org>,
	"vishal.l.verma@intel.com" <vishal.l.verma@intel.com>,
	 "dave.jiang@intel.com" <dave.jiang@intel.com>,
	"agk@redhat.com" <agk@redhat.com>,
	 "snitzer@redhat.com" <snitzer@redhat.com>,
	"dm-devel@redhat.com" <dm-devel@redhat.com>,
	 "ira.weiny@intel.com" <ira.weiny@intel.com>,
	"willy@infradead.org" <willy@infradead.org>,
	 "vgoyal@redhat.com" <vgoyal@redhat.com>,
	 "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	 "nvdimm@lists.linux.dev" <nvdimm@lists.linux.dev>,
	 "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	 "linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>
Subject: Re: [dm-devel] [PATCH 0/6] dax poison recovery with RWF_RECOVERY_DATA flag
Date: Tue, 2 Nov 2021 09:03:55 -0700	[thread overview]
Message-ID: <CAPcyv4hK18DetEf9+NcDqM5y07Vp-=nhysHJ3JSnKbS-ET2ppw@mail.gmail.com> (raw)
In-Reply-To: <YXj2lwrxRxHdr4hb@infradead.org>

On Tue, Oct 26, 2021 at 11:50 PM Christoph Hellwig <hch@infradead.org> wrote:
>
> On Fri, Oct 22, 2021 at 08:52:55PM +0000, Jane Chu wrote:
> > Thanks - I try to be honest.  As far as I can tell, the argument
> > about the flag is a philosophical argument between two views.
> > One view assumes design based on perfect hardware, and media error
> > belongs to the category of brokenness. Another view sees media
> > error as a build-in hardware component and make design to include
> > dealing with such errors.
>
> No, I don't think so.  Bit errors do happen in all media, which is
> why devices are built to handle them.  It is just the Intel-style
> pmem interface to handle them which is completely broken.

No, any media can report checksum / parity errors. NVME also seems to
do a poor job with multi-bit ECC errors consumed from DRAM. There is
nothing "pmem" or "Intel" specific here.

> > errors in mind from start.  I guess I'm trying to articulate why
> > it is acceptable to include the RWF_DATA_RECOVERY flag to the
> > existing RWF_ flags. - this way, pwritev2 remain fast on fast path,
> > and its slow path (w/ error clearing) is faster than other alternative.
> > Other alternative being 1 system call to clear the poison, and
> > another system call to run the fast pwrite for recovery, what
> > happens if something happened in between?
>
> Well, my point is doing recovery from bit errors is by definition not
> the fast path.  Which is why I'd rather keep it away from the pmem
> read/write fast path, which also happens to be the (much more important)
> non-pmem read/write path.

I would expect this interface to be useful outside of pmem as a
"failfast" or "try harder to recover" flag for reading over media
errors.

  parent reply	other threads:[~2021-11-02 16:04 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-21  0:10 [PATCH 0/6] dax poison recovery with RWF_RECOVERY_DATA flag Jane Chu
2021-10-21  0:10 ` [PATCH 1/6] dax: introduce RWF_RECOVERY_DATA flag to preadv2() and pwritev2() Jane Chu
2021-10-21  0:10 ` [PATCH 2/6] dax: prepare dax_direct_access() API with DAXDEV_F_RECOVERY flag Jane Chu
2021-10-21 11:20   ` Christoph Hellwig
2021-10-21 18:19     ` Jane Chu
2021-10-21  0:10 ` [PATCH 3/6] pmem: pmem_dax_direct_access() to honor the " Jane Chu
2021-10-21 11:23   ` Christoph Hellwig
2021-10-21 18:24     ` Jane Chu
2021-10-21  0:10 ` [PATCH 4/6] dm,dax,pmem: prepare dax_copy_to/from_iter() APIs with DAXDEV_F_RECOVERY Jane Chu
2021-10-21 11:27   ` Christoph Hellwig
2021-10-22  0:49     ` Jane Chu
2021-10-22  1:41       ` correction: " Jane Chu
2021-10-22  5:33       ` Christoph Hellwig
2021-10-22 20:30         ` Jane Chu
2021-10-21  0:10 ` [PATCH 5/6] dax,pmem: Add data recovery feature to pmem_copy_to/from_iter() Jane Chu
2021-10-21 11:28   ` Christoph Hellwig
2021-10-22  0:58     ` Jane Chu
2021-10-21  0:10 ` [PATCH 6/6] dm: Ensure dm honors DAXDEV_F_RECOVERY flag on dax only Jane Chu
2021-10-21 11:31 ` [dm-devel] [PATCH 0/6] dax poison recovery with RWF_RECOVERY_DATA flag Christoph Hellwig
2021-10-22  1:37   ` Jane Chu
2021-10-22  1:58     ` Darrick J. Wong
2021-10-22  5:38       ` Christoph Hellwig
2021-10-22  5:36     ` Christoph Hellwig
2021-10-22 20:52       ` Jane Chu
2021-10-27  6:49         ` Christoph Hellwig
2021-10-28  0:24           ` Darrick J. Wong
2021-10-28 22:59             ` Dave Chinner
2021-10-29 11:46               ` Pavel Begunkov
2021-10-29 16:57                 ` Darrick J. Wong
2021-10-29 19:23                   ` Pavel Begunkov
2021-10-29 20:08                     ` Darrick J. Wong
2021-10-31 13:27                       ` Pavel Begunkov
2021-10-29 18:53                 ` Jane Chu
2021-10-29 22:32                 ` Dave Chinner
2021-10-31 13:19                   ` Pavel Begunkov
2021-11-01  2:31                     ` Matthew Wilcox
2021-11-02  6:18             ` Christoph Hellwig
2021-11-02 19:57               ` Dan Williams
2021-11-03 16:58                 ` Christoph Hellwig
2021-11-03 20:33                   ` Dan Williams
2021-11-04  8:30                     ` Christoph Hellwig
2021-11-04 12:29                       ` Matthew Wilcox
2021-11-04 16:24                       ` Dan Williams
2021-11-04 17:43                         ` Christoph Hellwig
2021-11-04 17:50                           ` Dan Williams
2021-11-04 18:05                           ` Matthew Wilcox
2021-11-04 18:33                         ` Jane Chu
2021-11-04 19:00                           ` Dan Williams
2021-11-04 20:27                             ` Jane Chu
2021-11-05  0:46                               ` Dan Williams
2021-11-05  1:35                                 ` Dan Williams
2021-11-05  5:56                             ` Christoph Hellwig
2021-11-03 18:09               ` Jane Chu
2021-11-04  6:21                 ` Dan Williams
2021-11-04  8:36                   ` Christoph Hellwig
2021-11-04 16:08                     ` Dan Williams
2021-11-04 17:46                       ` Christoph Hellwig
2021-11-04  8:21                 ` Christoph Hellwig
2021-11-02 16:12             ` Dan Williams
2021-11-02 16:03           ` Dan Williams [this message]
2021-11-03 16:53             ` Christoph Hellwig
2021-11-06  7:41             ` Lukas Straub

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