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Groups > linux.kernel > #1564720
| From | Dan Williams <dan.j.williams@intel.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm |
| Date | 2017-01-23 08:20 +0100 |
| Message-ID | <t2H50-3rt-7@gated-at.bofh.it> (permalink) |
| References | (5 earlier) <t2uUa-46y-5@gated-at.bofh.it> <t2vdv-4dV-11@gated-at.bofh.it> <t2vdw-4dV-19@gated-at.bofh.it> <t2vnb-4hj-9@gated-at.bofh.it> <t2Gsh-2Za-1@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Sun, Jan 22, 2017 at 10:37 PM, Matthew Wilcox <mawilcox@microsoft.com> wrote: > From: Christoph Hellwig [mailto:hch@lst.de] >> On Sun, Jan 22, 2017 at 06:39:28PM +0000, Matthew Wilcox wrote: >> > Two guests on the same physical machine (or a guest and a host) have access >> > to the same set of physical addresses. This might be an NV-DIMM, or it might >> > just be DRAM (for the purposes of reducing guest overhead). The network >> > filesystem has been enhanced with a call to allow the client to ask the server >> > "What is the physical address for this range of bytes in this file?" >> > >> > We don't want to use the guest pagecache here. That's antithetical to the >> > second usage, and it's inefficient for the first usage. >> >> And the answer is that you need a dax device for whatever memoery exposed >> in this way, as it needs to show up in the memory map for example. > > Wow, DAX devices look painful and awful. I certainly don't want to be exposing the memory fronted by my network filesystem to userspace to access. That just seems like a world of pain and bad experiences. Absolutely the filesystem (or perhaps better, the ACPI tables) need to mark that chunk of memory as reserved, but it's definitely not available for anyone to access without the filesystem being aware. > > Even if we let the filesystem create a DAX device that doesn't show up in /dev (for example), Dan's patches don't give us a way to go from a file on the filesystem to a set of dax_ops. And it does need to be a per-file operation, eg to support a file on an XFS volume which might be on a RT device or a normal device. That was why I leaned towards an address_space operation, but I'd be happy to see an inode_operation instead. How about we solve the copy_from_user() abuse first before we hijack this thread for some future feature that afaics has no patches posted yet. An incremental step towards disentangling filesystem-dax from block_devices is a lookup mechanism to go from a block_device to a dax object that holds dax_ops. When this brave new filesystem enabling appears it can grow a mechanism to lookup, or mount on, the dax object directly. One idea is to just hang a pointer to this dax object off of bdev_inode, set at bdev open() time.
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[PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Dan Williams <dan.j.williams@intel.com> - 2017-01-20 05:00 +0100
[PATCH 08/13] x86, libnvdimm, dax: stop abusing __copy_user_nocache Dan Williams <dan.j.williams@intel.com> - 2017-01-20 05:00 +0100
[PATCH 10/13] libnvdimm, pmem: fix persistence warning Dan Williams <dan.j.williams@intel.com> - 2017-01-20 05:00 +0100
[PATCH 07/13] x86, libnvdimm, pmem: move arch_invalidate_pmem() to libnvdimm Dan Williams <dan.j.williams@intel.com> - 2017-01-20 05:00 +0100
[PATCH 01/13] x86, dax, pmem: remove indirection around memcpy_from_pmem() Dan Williams <dan.j.williams@intel.com> - 2017-01-20 05:00 +0100
[PATCH 05/13] x86, dax: replace clear_pmem() with open coded memset + dax_ops->flush Dan Williams <dan.j.williams@intel.com> - 2017-01-20 05:00 +0100
Re: [PATCH 05/13] x86, dax: replace clear_pmem() with open coded memset + dax_ops->flush Jan Kara <jack@suse.cz> - 2017-01-20 11:50 +0100
Re: [PATCH 05/13] x86, dax: replace clear_pmem() with open coded memset + dax_ops->flush Dan Williams <dan.j.williams@intel.com> - 2017-01-20 16:40 +0100
[PATCH 03/13] x86, dax, pmem: introduce 'copy_from_iter' dax operation Dan Williams <dan.j.williams@intel.com> - 2017-01-20 05:00 +0100
[PATCH 13/13] libnvdimm, pmem: disable dax flushing for 'cache flush on fail' platforms Dan Williams <dan.j.williams@intel.com> - 2017-01-20 05:00 +0100
[PATCH 09/13] libnvdimm, pmem: implement cache bypass for all copy_from_iter() operations Dan Williams <dan.j.williams@intel.com> - 2017-01-20 05:00 +0100
[PATCH 04/13] dax, pmem: introduce an optional 'flush' dax operation Dan Williams <dan.j.williams@intel.com> - 2017-01-20 05:00 +0100
[PATCH 06/13] x86, dax, libnvdimm: move wb_cache_pmem() to libnvdimm Dan Williams <dan.j.williams@intel.com> - 2017-01-20 05:00 +0100
RE: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Matthew Wilcox <mawilcox@microsoft.com> - 2017-01-21 17:30 +0100
Re: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Christoph Hellwig <hch@lst.de> - 2017-01-21 19:00 +0100
RE: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Matthew Wilcox <mawilcox@microsoft.com> - 2017-01-22 16:50 +0100
Re: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Christoph Hellwig <hch@lst.de> - 2017-01-22 17:40 +0100
RE: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Matthew Wilcox <mawilcox@microsoft.com> - 2017-01-22 19:20 +0100
Re: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Christoph Hellwig <hch@lst.de> - 2017-01-22 19:40 +0100
RE: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Matthew Wilcox <mawilcox@microsoft.com> - 2017-01-22 19:40 +0100
Re: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Christoph Hellwig <hch@lst.de> - 2017-01-22 19:50 +0100
RE: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Matthew Wilcox <mawilcox@microsoft.com> - 2017-01-23 07:40 +0100
Re: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Dan Williams <dan.j.williams@intel.com> - 2017-01-23 08:20 +0100
Re: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Christoph Hellwig <hch@lst.de> - 2017-01-23 17:10 +0100
Re: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Dan Williams <dan.j.williams@intel.com> - 2017-01-23 18:20 +0100
Re: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Christoph Hellwig <hch@lst.de> - 2017-01-23 19:10 +0100
Re: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Dan Williams <dan.j.williams@intel.com> - 2017-01-23 19:40 +0100
Re: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Christoph Hellwig <hch@lst.de> - 2017-01-23 17:00 +0100
Re: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Dan Williams <dan.j.williams@intel.com> - 2017-01-22 18:40 +0100
Re: [PATCH 00/13] dax, pmem: move cpu cache maintenance to libnvdimm Christoph Hellwig <hch@lst.de> - 2017-01-23 17:10 +0100
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