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From: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Heiko Carstens <hca@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Dan Williams <dan.j.williams@intel.com>,
	nvdimm@lists.linux.dev, linux-s390@vger.kernel.org
Subject: Re: can we finally kill off CONFIG_FS_DAX_LIMITED
Date: Mon, 23 Aug 2021 16:05:46 +0200	[thread overview]
Message-ID: <20210823160546.0bf243bf@thinkpad> (raw)
In-Reply-To: <20210820054340.GA28560@lst.de>

On Fri, 20 Aug 2021 07:43:40 +0200
Christoph Hellwig <hch@lst.de> wrote:

> Hi all,
> 
> looking at the recent ZONE_DEVICE related changes we still have a
> horrible maze of different code paths.  I already suggested to
> depend on ARCH_HAS_PTE_SPECIAL for ZONE_DEVICE there, which all modern
> architectures have anyway.  But the other odd special case is
> CONFIG_FS_DAX_LIMITED which is just used for the xpram driver.  Does
> this driver still see use?  If so can we make it behave like the
> other DAX drivers and require a pgmap?  I think the biggest missing
> part would be to implement ARCH_HAS_PTE_DEVMAP for s390.

Puh, yes, that seems to be needed in order to enable ZONE_DEVICE, and
then we could use devm_memremap_pages(), at least that was my plan
some time ago. However, either the ARCH_HAS_PTE_DEVMAP dependency
is new, or I overlooked it before, but we do not have any free bits
in the pte left, so this is not going to work.

Would it strictly be necessary to implement ZONE_DEVICE, or would
it be enough if we would use e.g. add_memory() instead of just
adding the DCSS memory directly to the kernel mapping via
vmem_add_mapping()? That way we might at least get the struct pages,
but somehow it doesn't feel completely right.

  parent reply	other threads:[~2021-08-23 14:06 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-20  5:43 can we finally kill off CONFIG_FS_DAX_LIMITED Christoph Hellwig
2021-08-20 15:41 ` Dan Williams
2021-08-20 15:41   ` Dan Williams
2021-08-20 17:42   ` Dan Williams
2021-08-20 17:42     ` Dan Williams
2021-08-20 19:03     ` Gerald Schaefer
2021-08-24 14:17     ` Joao Martins
2021-08-23 14:05 ` Gerald Schaefer [this message]
2021-08-23 19:47   ` Gerald Schaefer
2021-08-23 20:21     ` Dan Williams
2021-08-23 20:21       ` Dan Williams
2021-08-24 14:09       ` Joao Martins
2021-08-24 14:53         ` Dan Williams
2021-08-24 14:53           ` Dan Williams
2021-08-24 18:24           ` Gerald Schaefer
2021-08-24 18:44             ` Dan Williams
2021-08-24 18:44               ` Dan Williams
2021-10-14 23:04               ` Jason Gunthorpe
2021-10-15  0:22                 ` Joao Martins
2021-10-18 23:30                   ` Jason Gunthorpe
2021-10-19  4:26                     ` Dan Williams
2021-10-19 14:20                       ` Jason Gunthorpe
2021-10-19 15:20                         ` Joao Martins
2021-10-19 15:38                         ` Felix Kuehling
2021-10-19 17:38                         ` Dan Williams
2021-10-19 17:54                           ` Jason Gunthorpe
2021-08-24  6:49   ` David Hildenbrand

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