From: Jason Gunthorpe <jgg@nvidia.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Alistair Popple <apopple@nvidia.com>,
linux-mm@kvack.org, david@fromorbit.com, jhubbard@nvidia.com,
rcampbell@nvidia.com, willy@infradead.org,
linux-fsdevel@vger.kernel.org, jack@suse.cz, djwong@kernel.org,
hch@lst.de, david@redhat.com, ruansy.fnst@fujitsu.com,
nvdimm@lists.linux.dev, linux-xfs@vger.kernel.org,
linux-ext4@vger.kernel.org, jglisse@redhat.com
Subject: Re: [RFC 00/10] fs/dax: Fix FS DAX page reference counts
Date: Thu, 11 Apr 2024 14:35:59 -0300 [thread overview]
Message-ID: <20240411173559.GX5383@nvidia.com> (raw)
In-Reply-To: <66181dd83f74e_15786294e8@dwillia2-mobl3.amr.corp.intel.com.notmuch>
On Thu, Apr 11, 2024 at 10:28:56AM -0700, Dan Williams wrote:
> Alistair Popple wrote:
> > FS DAX pages have always maintained their own page reference counts
> > without following the normal rules for page reference counting. In
> > particular pages are considered free when the refcount hits one rather
> > than zero and refcounts are not added when mapping the page.
>
> > Tracking this requires special PTE bits (PTE_DEVMAP) and a secondary
> > mechanism for allowing GUP to hold references on the page (see
> > get_dev_pagemap). However there doesn't seem to be any reason why FS
> > DAX pages need their own reference counting scheme.
>
> This is fair. However, for anyone coming in fresh to this situation
> maybe some more "how we get here" history helps. That longer story is
> here:
>
> http://lore.kernel.org/all/166579181584.2236710.17813547487183983273.stgit@dwillia2-xfh.jf.intel.com/
This never got merged? :(
Jason
next prev parent reply other threads:[~2024-04-11 17:36 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-11 0:57 [RFC 00/10] fs/dax: Fix FS DAX page reference counts Alistair Popple
2024-04-11 0:57 ` [RFC 01/10] mm/gup.c: Remove redundant check for PCI P2PDMA page Alistair Popple
2024-04-11 12:59 ` Jason Gunthorpe
2024-04-11 13:47 ` David Hildenbrand
2024-04-12 1:37 ` Alistair Popple
2024-04-11 0:57 ` [RFC 02/10] mm/hmm: Remove dead check for HugeTLB and FS DAX Alistair Popple
2024-04-11 12:25 ` Jason Gunthorpe
2024-04-11 13:37 ` Peter Xu
2024-04-12 1:28 ` Alistair Popple
2024-04-11 0:57 ` [RFC 03/10] pci/p2pdma: Don't initialise page refcount to one Alistair Popple
2024-04-11 12:29 ` Jason Gunthorpe
2024-04-12 5:40 ` Alistair Popple
2024-04-12 17:20 ` Dan Williams
2024-05-09 21:59 ` Logan Gunthorpe
2024-05-09 23:14 ` Alistair Popple
2024-04-11 0:57 ` [RFC 04/10] fs/dax: Don't track page mapping/index Alistair Popple
2024-04-12 15:22 ` Jan Kara
2024-04-12 17:31 ` Dan Williams
2024-04-15 7:03 ` Alistair Popple
2024-04-15 20:51 ` Dan Williams
2024-04-16 0:07 ` Alistair Popple
2024-04-16 0:36 ` Dan Williams
2024-04-12 17:21 ` Dan Williams
2024-04-11 0:57 ` [RFC 05/10] fs/dax: Refactor wait for dax idle page Alistair Popple
2024-04-12 14:37 ` Jan Kara
2024-04-13 20:19 ` John Hubbard
2024-04-15 8:41 ` Alistair Popple
2024-04-11 0:57 ` [RFC 06/10] fs/dax: Add dax_page_free callback Alistair Popple
2024-04-11 23:34 ` kernel test robot
2024-04-11 0:57 ` [RFC 07/10] mm: Allow compound zone device pages Alistair Popple
2024-04-11 12:32 ` Jason Gunthorpe
2024-04-11 14:10 ` Matthew Wilcox
2024-04-12 1:38 ` Alistair Popple
2024-04-11 0:57 ` [RFC 08/10] fs/dax: Properly refcount fs dax pages Alistair Popple
2024-04-11 21:08 ` kernel test robot
2024-04-11 0:57 ` [RFC 09/10] mm/khugepage.c: Warn if trying to scan devmap pmd Alistair Popple
2024-04-11 13:45 ` David Hildenbrand
2024-04-12 1:34 ` Alistair Popple
2024-04-11 0:57 ` [RFC 10/10] mm: Remove pXX_devmap Alistair Popple
2024-04-11 12:57 ` Jason Gunthorpe
2024-04-12 0:36 ` kernel test robot
2024-04-11 17:28 ` [RFC 00/10] fs/dax: Fix FS DAX page reference counts Dan Williams
2024-04-11 17:35 ` Jason Gunthorpe [this message]
2024-04-11 17:56 ` Dan Williams
2024-04-12 3:54 ` Alistair Popple
2024-04-12 6:55 ` Alistair Popple
2024-04-12 11:53 ` Jason Gunthorpe
2024-04-12 17:32 ` Dan Williams
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