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From: Christoph Hellwig <hch@infradead.org>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>
Subject: Re: [PATCH v2 3/3] dev-dax: add fallocate support to clear poison
Date: Mon, 19 Dec 2016 22:40:17 -0800	[thread overview]
Message-ID: <20161220064017.GA8390@infradead.org> (raw)
In-Reply-To: <CAPcyv4hQdOrFoct0bCYKciWffsV511zXX3oxQKHM+4vere6VtA@mail.gmail.com>

On Mon, Dec 19, 2016 at 04:46:00PM -0800, Dan Williams wrote:
> In the case of filesystem-dax (xfs or ext4) a punch hole operation is
> effective for clearing a media error.

Which at best is a third order side effect of what it actually does:
release allocated space.  Which is something we can do on various
block devices (SCSI with thin provisioning, device mapper) as well.

> It will deallocate blocks and
> the zeroing that is performed when the blocks are reallocated will
> clear media errors. We want the same semantic for device-dax.
> FALLOC_FL_PUNCH_HOLE triggers the driver stack to clear any media
> errors, although unlike the filesystem case there are no physical
> ranges de-allocated from the device. With support for this subset of
> fallocate we can avoid needing to add a custom ioctl for similar
> functionality.

It's in no way similar functionality.  It's absuing an interface for
something entirely different.

So NAK to this series.
_______________________________________________
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Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>
Subject: Re: [PATCH v2 3/3] dev-dax: add fallocate support to clear poison
Date: Mon, 19 Dec 2016 22:40:17 -0800	[thread overview]
Message-ID: <20161220064017.GA8390@infradead.org> (raw)
In-Reply-To: <CAPcyv4hQdOrFoct0bCYKciWffsV511zXX3oxQKHM+4vere6VtA@mail.gmail.com>

On Mon, Dec 19, 2016 at 04:46:00PM -0800, Dan Williams wrote:
> In the case of filesystem-dax (xfs or ext4) a punch hole operation is
> effective for clearing a media error.

Which at best is a third order side effect of what it actually does:
release allocated space.  Which is something we can do on various
block devices (SCSI with thin provisioning, device mapper) as well.

> It will deallocate blocks and
> the zeroing that is performed when the blocks are reallocated will
> clear media errors. We want the same semantic for device-dax.
> FALLOC_FL_PUNCH_HOLE triggers the driver stack to clear any media
> errors, although unlike the filesystem case there are no physical
> ranges de-allocated from the device. With support for this subset of
> fallocate we can avoid needing to add a custom ioctl for similar
> functionality.

It's in no way similar functionality.  It's absuing an interface for
something entirely different.

So NAK to this series.

  reply	other threads:[~2016-12-20  6:40 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-19 23:30 [PATCH v2 1/3] dev-dax: add support to display badblocks in sysfs for dev-dax Dave Jiang
2016-12-19 23:30 ` [PATCH v2 2/3] nvdimm-testing: providing dax support for nvdimm testing Dave Jiang
2016-12-19 23:30 ` [PATCH v2 3/3] dev-dax: add fallocate support to clear poison Dave Jiang
2016-12-20  0:46   ` Dan Williams
2016-12-20  0:46     ` Dan Williams
2016-12-20  6:40     ` Christoph Hellwig [this message]
2016-12-20  6:40       ` Christoph Hellwig
     [not found]   ` <148219024781.15885.1883996216561314302.stgit-Cxk7aZI4ujnJARH06PadV2t3HXsI98Cx0E9HWUfgJXw@public.gmane.org>
2016-12-20  6:04     ` Christoph Hellwig

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