From: Jason Gunthorpe <jgg@nvidia.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: akpm@linux-foundation.org, Jan Kara <jack@suse.cz>,
Christoph Hellwig <hch@lst.de>,
"Darrick J. Wong" <djwong@kernel.org>,
Matthew Wilcox <willy@infradead.org>,
John Hubbard <jhubbard@nvidia.com>,
linux-fsdevel@vger.kernel.org, nvdimm@lists.linux.dev,
linux-xfs@vger.kernel.org, linux-mm@kvack.org,
linux-ext4@vger.kernel.org
Subject: Re: [PATCH v2 00/18] Fix the DAX-gup mistake
Date: Tue, 20 Sep 2022 11:29:49 -0300 [thread overview]
Message-ID: <YynOXa8+jxxCjH5k@nvidia.com> (raw)
In-Reply-To: <166329930818.2786261.6086109734008025807.stgit@dwillia2-xfh.jf.intel.com>
On Thu, Sep 15, 2022 at 08:35:08PM -0700, Dan Williams wrote:
> This hackery continues the status of DAX pages as special cases in the
> VM. The thought being carrying the Xarray / mapping infrastructure
> forward still allows for the continuation of the page-less DAX effort.
> Otherwise, the work to convert DAX pages to behave like typical
> vm_normal_page() needs more investigation to untangle transparent huge
> page assumptions.
I see it differently, ZONE_DEVICE by definition is page-based. As long
as DAX is using ZONE_DEVICE it should follow the normal struct page
rules, including proper reference counting everywhere.
By not doing this DAX is causing all ZONE_DEVICE users to suffer
because we haven't really special cased just DAX out of all the other
users.
If there is some kind of non-struct page future, then it will not be
ZONE_DEVICE and it will have its own mechanisms, somehow.
So, we should be systematically stripping away all the half-backed
non-struct page stuff from ZONE_DEVICE as a matter of principle. DAX
included, whatever DAX's future may hold.
The pte bit and the missing refcounting in the page table paths is the
remaining big issue and I hope we fix it. The main problem is that
FS-DAX must create compound pages for the 2M page size.
Jason
next prev parent reply other threads:[~2022-09-20 14:29 UTC|newest]
Thread overview: 84+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-16 3:35 [PATCH v2 00/18] Fix the DAX-gup mistake Dan Williams
2022-09-16 3:35 ` [PATCH v2 01/18] fsdax: Wait on @page not @page->_refcount Dan Williams
2022-09-20 14:30 ` Jason Gunthorpe
2022-09-16 3:35 ` [PATCH v2 02/18] fsdax: Use dax_page_idle() to document DAX busy page checking Dan Williams
2022-09-20 14:31 ` Jason Gunthorpe
2022-09-16 3:35 ` [PATCH v2 03/18] fsdax: Include unmapped inodes for page-idle detection Dan Williams
2022-09-16 3:35 ` [PATCH v2 04/18] ext4: Add ext4_break_layouts() to the inode eviction path Dan Williams
2022-09-16 3:35 ` [PATCH v2 05/18] xfs: Add xfs_break_layouts() " Dan Williams
2022-09-18 22:57 ` Dave Chinner
2022-09-19 16:11 ` Dan Williams
2022-09-19 21:29 ` Dave Chinner
2022-09-20 16:44 ` Dan Williams
2022-09-21 22:14 ` Dave Chinner
2022-09-21 22:28 ` Jason Gunthorpe
2022-09-23 0:18 ` Dave Chinner
2022-09-23 0:41 ` Dan Williams
2022-09-23 2:10 ` Dave Chinner
2022-09-23 9:38 ` Jan Kara
2022-09-23 23:06 ` Dan Williams
2022-09-25 23:54 ` Dave Chinner
2022-09-26 14:10 ` Jan Kara
2022-09-29 23:33 ` Dan Williams
2022-09-30 13:41 ` Jan Kara
2022-09-30 17:56 ` Dan Williams
2022-09-30 18:06 ` Jason Gunthorpe
2022-09-30 18:46 ` Dan Williams
2022-10-03 7:55 ` Jan Kara
2022-09-23 12:39 ` Jason Gunthorpe
2022-09-26 0:34 ` Dave Chinner
2022-09-26 13:04 ` Jason Gunthorpe
2022-09-22 0:02 ` Dan Williams
2022-09-22 0:10 ` Jason Gunthorpe
2022-09-16 3:35 ` [PATCH v2 06/18] fsdax: Rework dax_layout_busy_page() to dax_zap_mappings() Dan Williams
2022-09-16 3:35 ` [PATCH v2 07/18] fsdax: Update dax_insert_entry() calling convention to return an error Dan Williams
2022-09-16 3:35 ` [PATCH v2 08/18] fsdax: Cleanup dax_associate_entry() Dan Williams
2022-09-16 3:36 ` [PATCH v2 09/18] fsdax: Rework dax_insert_entry() calling convention Dan Williams
2022-09-16 3:36 ` [PATCH v2 10/18] fsdax: Manage pgmap references at entry insertion and deletion Dan Williams
2022-09-21 14:03 ` Jason Gunthorpe
2022-09-21 15:18 ` Dan Williams
2022-09-21 21:38 ` Dan Williams
2022-09-21 22:07 ` Jason Gunthorpe
2022-09-22 0:14 ` Dan Williams
2022-09-22 0:25 ` Jason Gunthorpe
2022-09-22 2:17 ` Dan Williams
2022-09-22 17:55 ` Jason Gunthorpe
2022-09-22 21:54 ` Dan Williams
2022-09-23 1:36 ` Dave Chinner
2022-09-23 2:01 ` Dan Williams
2022-09-23 13:24 ` Jason Gunthorpe
2022-09-23 16:29 ` Dan Williams
2022-09-23 17:42 ` Jason Gunthorpe
2022-09-23 19:03 ` Dan Williams
2022-09-23 19:23 ` Jason Gunthorpe
2022-09-27 6:07 ` Alistair Popple
2022-09-27 12:56 ` Jason Gunthorpe
2022-09-16 3:36 ` [PATCH v2 11/18] devdax: Minor warning fixups Dan Williams
2022-09-16 3:36 ` [PATCH v2 12/18] devdax: Move address_space helpers to the DAX core Dan Williams
2022-09-27 6:20 ` Alistair Popple
2022-09-29 22:38 ` Dan Williams
2022-09-16 3:36 ` [PATCH v2 13/18] dax: Prep mapping helpers for compound pages Dan Williams
2022-09-21 14:06 ` Jason Gunthorpe
2022-09-21 15:19 ` Dan Williams
2022-09-16 3:36 ` [PATCH v2 14/18] devdax: add PUD support to the DAX mapping infrastructure Dan Williams
2022-09-16 3:36 ` [PATCH v2 15/18] devdax: Use dax_insert_entry() + dax_delete_mapping_entry() Dan Williams
2022-09-21 14:10 ` Jason Gunthorpe
2022-09-21 15:48 ` Dan Williams
2022-09-21 22:23 ` Jason Gunthorpe
2022-09-22 0:15 ` Dan Williams
2022-09-16 3:36 ` [PATCH v2 16/18] mm/memremap_pages: Support initializing pages to a zero reference count Dan Williams
2022-09-21 15:24 ` Jason Gunthorpe
2022-09-21 23:45 ` Dan Williams
2022-09-22 0:03 ` Alistair Popple
2022-09-22 0:04 ` Jason Gunthorpe
2022-09-22 0:34 ` Dan Williams
2022-09-22 1:36 ` Alistair Popple
2022-09-22 2:34 ` Dan Williams
2022-09-26 6:17 ` Alistair Popple
2022-09-22 0:13 ` John Hubbard
2022-09-16 3:36 ` [PATCH v2 17/18] fsdax: Delete put_devmap_managed_page_refs() Dan Williams
2022-09-16 3:36 ` [PATCH v2 18/18] mm/gup: Drop DAX pgmap accounting Dan Williams
2022-09-20 14:29 ` Jason Gunthorpe [this message]
2022-09-20 16:50 ` [PATCH v2 00/18] Fix the DAX-gup mistake Dan Williams
2022-11-09 0:20 ` Andrew Morton
2022-11-09 11:38 ` Jan Kara
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