From: Jason Gunthorpe <jgg@mellanox.com>
To: Christoph Hellwig <hch@lst.de>
Cc: "Dan Williams" <dan.j.williams@intel.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Ben Skeggs" <bskeggs@redhat.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"nouveau@lists.freedesktop.org" <nouveau@lists.freedesktop.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 04/22] mm: don't clear ->mapping in hmm_devmem_free
Date: Thu, 13 Jun 2019 19:05:07 +0000 [thread overview]
Message-ID: <20190613190501.GQ22062@mellanox.com> (raw)
In-Reply-To: <20190613094326.24093-5-hch@lst.de>
On Thu, Jun 13, 2019 at 11:43:07AM +0200, Christoph Hellwig wrote:
> ->mapping isn't even used by HMM users, and the field at the same offset
> in the zone_device part of the union is declared as pad. (Which btw is
> rather confusing, as DAX uses ->pgmap and ->mapping from two different
> sides of the union, but DAX doesn't use hmm_devmem_free).
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> mm/hmm.c | 2 --
> 1 file changed, 2 deletions(-)
Hurm, is hmm following this comment from mm_types.h?
* If you allocate the page using alloc_pages(), you can use some of the
* space in struct page for your own purposes. The five words in the main
* union are available, except for bit 0 of the first word which must be
* kept clear. Many users use this word to store a pointer to an object
* which is guaranteed to be aligned. If you use the same storage as
* page->mapping, you must restore it to NULL before freeing the page.
Maybe the assumption was that a driver is using ->mapping ?
However, nouveau is the only driver that uses this path, and it never
touches page->mapping either (nor in -next).
It looks like if a driver were to start using mapping then the driver
should be responsible to set it back to NULL before being done with
the page.
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Jason
WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgg-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
To: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Cc: "linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org"
<linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org>,
"nouveau-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org"
<nouveau-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org>,
"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org"
<dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org>,
"linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org"
<linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>,
"Jérôme Glisse" <jglisse-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
"Ben Skeggs" <bskeggs-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
"linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Subject: Re: [PATCH 04/22] mm: don't clear ->mapping in hmm_devmem_free
Date: Thu, 13 Jun 2019 19:05:07 +0000 [thread overview]
Message-ID: <20190613190501.GQ22062@mellanox.com> (raw)
In-Reply-To: <20190613094326.24093-5-hch-jcswGhMUV9g@public.gmane.org>
On Thu, Jun 13, 2019 at 11:43:07AM +0200, Christoph Hellwig wrote:
> ->mapping isn't even used by HMM users, and the field at the same offset
> in the zone_device part of the union is declared as pad. (Which btw is
> rather confusing, as DAX uses ->pgmap and ->mapping from two different
> sides of the union, but DAX doesn't use hmm_devmem_free).
>
> Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
> ---
> mm/hmm.c | 2 --
> 1 file changed, 2 deletions(-)
Hurm, is hmm following this comment from mm_types.h?
* If you allocate the page using alloc_pages(), you can use some of the
* space in struct page for your own purposes. The five words in the main
* union are available, except for bit 0 of the first word which must be
* kept clear. Many users use this word to store a pointer to an object
* which is guaranteed to be aligned. If you use the same storage as
* page->mapping, you must restore it to NULL before freeing the page.
Maybe the assumption was that a driver is using ->mapping ?
However, nouveau is the only driver that uses this path, and it never
touches page->mapping either (nor in -next).
It looks like if a driver were to start using mapping then the driver
should be responsible to set it back to NULL before being done with
the page.
Reviewed-by: Jason Gunthorpe <jgg-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Jason
next prev parent reply other threads:[~2019-06-13 19:05 UTC|newest]
Thread overview: 254+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-13 9:43 dev_pagemap related cleanups Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` [PATCH 01/22] mm: remove the unused ARCH_HAS_HMM_DEVICE Kconfig option Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 18:30 ` Jason Gunthorpe
2019-06-13 18:30 ` Jason Gunthorpe
2019-06-13 18:30 ` Jason Gunthorpe
2019-06-13 9:43 ` [PATCH 02/22] mm: remove the struct hmm_device infrastructure Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 18:46 ` Jason Gunthorpe
2019-06-13 18:46 ` Jason Gunthorpe
2019-06-13 18:46 ` Jason Gunthorpe
2019-06-13 23:06 ` [Nouveau] " John Hubbard
2019-06-13 23:06 ` John Hubbard
2019-06-13 23:06 ` [Nouveau] " John Hubbard
2019-06-13 9:43 ` [PATCH 03/22] mm: remove hmm_devmem_add_resource Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 18:52 ` Jason Gunthorpe
2019-06-13 18:52 ` Jason Gunthorpe
2019-06-14 6:19 ` Christoph Hellwig
2019-06-14 0:54 ` [Nouveau] " John Hubbard
2019-06-14 0:54 ` John Hubbard
2019-06-14 0:54 ` [Nouveau] " John Hubbard
2019-06-20 19:32 ` Michal Hocko
2019-06-13 9:43 ` [PATCH 04/22] mm: don't clear ->mapping in hmm_devmem_free Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 19:05 ` Jason Gunthorpe [this message]
2019-06-13 19:05 ` Jason Gunthorpe
2019-06-14 6:21 ` Christoph Hellwig
2019-06-14 6:21 ` Christoph Hellwig
2019-06-14 1:46 ` John Hubbard
2019-06-14 1:46 ` John Hubbard
2019-06-14 1:46 ` John Hubbard
2019-06-20 19:36 ` Michal Hocko
2019-06-20 19:36 ` Michal Hocko
2019-06-13 9:43 ` [PATCH 05/22] mm: export alloc_pages_vma Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-14 1:47 ` John Hubbard
2019-06-14 1:47 ` John Hubbard
2019-06-14 1:47 ` John Hubbard
2019-06-14 6:23 ` Christoph Hellwig
2019-06-20 19:17 ` Michal Hocko
2019-06-24 18:24 ` Dan Williams
2019-06-24 18:24 ` Dan Williams
2019-06-25 7:23 ` Christoph Hellwig
2019-06-25 7:23 ` Christoph Hellwig
2019-06-25 15:00 ` Michal Hocko
2019-06-25 15:00 ` Michal Hocko
2019-06-25 18:03 ` Dan Williams
2019-06-25 18:03 ` Dan Williams
2019-06-25 19:00 ` Michal Hocko
2019-06-25 19:00 ` Michal Hocko
2019-06-25 19:52 ` Dan Williams
2019-06-25 19:52 ` Dan Williams
2019-06-26 5:46 ` Michal Hocko
2019-06-26 5:46 ` Michal Hocko
2019-06-26 5:46 ` Michal Hocko
2019-06-26 16:14 ` Dan Williams
2019-06-27 6:41 ` Michal Hocko
2019-06-27 6:41 ` Michal Hocko
2019-06-27 6:41 ` Michal Hocko
2019-06-13 9:43 ` [PATCH 06/22] mm: factor out a devm_request_free_mem_region helper Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 19:16 ` Jason Gunthorpe
2019-06-13 19:16 ` Jason Gunthorpe
2019-06-14 6:24 ` Christoph Hellwig
2019-06-14 6:24 ` Christoph Hellwig
2019-06-15 2:21 ` John Hubbard
2019-06-15 2:21 ` John Hubbard
2019-06-15 2:21 ` John Hubbard
2019-06-15 14:30 ` Christoph Hellwig
2019-06-15 14:30 ` Christoph Hellwig
2019-06-13 9:43 ` [PATCH 07/22] memremap: move dev_pagemap callbacks into a separate structure Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 19:18 ` Jason Gunthorpe
2019-06-13 19:18 ` Jason Gunthorpe
2019-06-13 19:18 ` Jason Gunthorpe
2019-06-13 20:14 ` Logan Gunthorpe
2019-06-13 20:14 ` Logan Gunthorpe
2019-06-13 9:43 ` [PATCH 08/22] memremap: pass a struct dev_pagemap to ->kill Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 19:26 ` Jason Gunthorpe
2019-06-13 19:26 ` Jason Gunthorpe
2019-06-13 20:12 ` Logan Gunthorpe
2019-06-13 20:12 ` Logan Gunthorpe
2019-06-13 20:12 ` Logan Gunthorpe
2019-06-13 20:15 ` Dan Williams
2019-06-13 20:15 ` Dan Williams
2019-06-13 9:43 ` [PATCH 09/22] memremap: lift the devmap_enable manipulation into devm_memremap_pages Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 19:34 ` Jason Gunthorpe
2019-06-13 19:34 ` Jason Gunthorpe
2019-06-13 19:34 ` Jason Gunthorpe
2019-06-13 20:13 ` Dan Williams
2019-06-13 20:13 ` Dan Williams
2019-06-14 6:28 ` Christoph Hellwig
2019-06-14 6:28 ` Christoph Hellwig
2019-06-14 6:28 ` Christoph Hellwig
2019-06-13 9:43 ` [PATCH 10/22] memremap: add a migrate callback to struct dev_pagemap_ops Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 23:42 ` Ralph Campbell
2019-06-13 23:42 ` Ralph Campbell
2019-06-13 23:42 ` Ralph Campbell
2019-06-14 6:33 ` Christoph Hellwig
2019-06-14 6:33 ` Christoph Hellwig
2019-06-14 6:33 ` Christoph Hellwig
2019-06-13 9:43 ` [PATCH 11/22] memremap: remove the data field in struct dev_pagemap Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 19:37 ` Jason Gunthorpe
2019-06-13 19:37 ` Jason Gunthorpe
2019-06-13 19:37 ` Jason Gunthorpe
2019-06-13 9:43 ` [PATCH 12/22] memremap: provide an optional internal refcount " Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` [PATCH 13/22] device-dax: use the dev_pagemap internal refcount Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-14 0:22 ` Ira Weiny
2019-06-14 0:22 ` Ira Weiny
2019-06-14 0:22 ` Ira Weiny
2019-06-14 6:35 ` Christoph Hellwig
2019-06-14 6:35 ` Christoph Hellwig
2019-06-13 9:43 ` [PATCH 14/22] nouveau: use alloc_page_vma directly Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 19:39 ` Jason Gunthorpe
2019-06-13 19:39 ` Jason Gunthorpe
2019-06-13 9:43 ` [PATCH 15/22] nouveau: use devm_memremap_pages directly Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` [PATCH 16/22] mm: remove hmm_vma_alloc_locked_page Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` [PATCH 17/22] mm: remove hmm_devmem_add Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 19:42 ` Jason Gunthorpe
2019-06-13 19:42 ` Jason Gunthorpe
2019-06-14 6:39 ` Christoph Hellwig
2019-06-13 9:43 ` [PATCH 18/22] mm: mark DEVICE_PUBLIC as broken Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 19:44 ` Jason Gunthorpe
2019-06-13 19:44 ` Jason Gunthorpe
2019-06-13 19:44 ` Jason Gunthorpe
2019-06-13 19:53 ` Ralph Campbell
2019-06-13 19:53 ` Ralph Campbell
2019-06-13 19:58 ` Jason Gunthorpe
2019-06-13 19:58 ` Jason Gunthorpe
2019-06-13 19:58 ` Jason Gunthorpe
2019-06-14 0:43 ` Ira Weiny
2019-06-14 0:43 ` Ira Weiny
2019-06-14 0:43 ` Ira Weiny
2019-06-14 1:23 ` John Hubbard
2019-06-14 1:23 ` John Hubbard
2019-06-14 1:23 ` John Hubbard
2019-06-19 19:27 ` Jason Gunthorpe
2019-06-19 19:27 ` Jason Gunthorpe
2019-06-19 19:46 ` Dan Williams
2019-06-19 19:46 ` Dan Williams
2019-06-26 3:15 ` John Hubbard
2019-06-26 3:15 ` John Hubbard
2019-06-26 3:15 ` John Hubbard
2019-06-26 5:45 ` Michal Hocko
2019-06-26 5:45 ` Michal Hocko
2019-06-26 5:45 ` Michal Hocko
2019-06-26 6:07 ` John Hubbard
2019-06-26 6:07 ` John Hubbard
2019-06-14 6:43 ` Christoph Hellwig
2019-06-14 6:43 ` Christoph Hellwig
2019-06-20 19:26 ` Michal Hocko
2019-06-25 7:29 ` Christoph Hellwig
2019-06-25 11:44 ` Jason Gunthorpe
2019-06-25 11:44 ` Jason Gunthorpe
2019-06-25 11:44 ` Jason Gunthorpe
2019-06-25 11:59 ` Christoph Hellwig
2019-06-13 9:43 ` [PATCH 19/22] mm: simplify ZONE_DEVICE page private data Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` [PATCH 20/22] mm: sort out the DEVICE_PRIVATE Kconfig mess Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 19:55 ` Jason Gunthorpe
2019-06-13 19:55 ` Jason Gunthorpe
2019-06-13 9:43 ` [PATCH 21/22] mm: remove the HMM config option Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 20:01 ` Jason Gunthorpe
2019-06-13 20:01 ` Jason Gunthorpe
2019-06-14 6:47 ` Christoph Hellwig
2019-06-14 6:47 ` Christoph Hellwig
2019-06-14 6:47 ` Christoph Hellwig
2019-06-13 9:43 ` [PATCH 22/22] mm: don't select MIGRATE_VMA_HELPER from HMM_MIRROR Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 9:43 ` Christoph Hellwig
2019-06-13 20:04 ` Jason Gunthorpe
2019-06-13 20:04 ` Jason Gunthorpe
2019-06-13 20:04 ` Jason Gunthorpe
2019-06-14 1:53 ` [Nouveau] " John Hubbard
2019-06-14 1:53 ` John Hubbard
2019-06-14 1:53 ` John Hubbard
2019-06-14 6:48 ` Christoph Hellwig
2019-06-14 6:48 ` Christoph Hellwig
2019-06-13 14:16 ` dev_pagemap related cleanups Jason Gunthorpe
2019-06-13 14:16 ` Jason Gunthorpe
2019-06-14 6:12 ` Christoph Hellwig
2019-06-14 6:12 ` Christoph Hellwig
2019-06-14 6:12 ` Christoph Hellwig
2019-06-13 18:27 ` Dan Williams
2019-06-13 18:27 ` Dan Williams
2019-06-13 18:27 ` Dan Williams
2019-06-13 20:17 ` Logan Gunthorpe
2019-06-13 20:17 ` Logan Gunthorpe
2019-06-13 20:21 ` Dan Williams
2019-06-13 20:24 ` Logan Gunthorpe
2019-06-13 20:24 ` Logan Gunthorpe
2019-06-13 20:48 ` Andrew Morton
2019-06-13 20:48 ` Andrew Morton
2019-06-13 20:48 ` Andrew Morton
2019-06-13 20:40 ` Jason Gunthorpe
2019-06-13 20:40 ` Jason Gunthorpe
2019-06-13 20:40 ` Jason Gunthorpe
2019-06-13 21:21 ` Christoph Hellwig
2019-06-13 21:21 ` Christoph Hellwig
2019-06-13 23:10 ` Jason Gunthorpe
2019-06-13 23:10 ` Jason Gunthorpe
2019-06-13 23:10 ` Jason Gunthorpe
2019-06-14 6:14 ` Christoph Hellwig
2019-06-14 6:14 ` Christoph Hellwig
2019-06-14 6:14 ` Christoph Hellwig
2019-06-14 0:31 ` Ira Weiny
2019-06-14 0:31 ` Ira Weiny
2019-06-14 0:31 ` Ira Weiny
2019-06-14 6:13 ` Christoph Hellwig
2019-06-14 6:13 ` Christoph Hellwig
2019-06-15 1:14 ` Dan Williams
2019-06-15 1:14 ` Dan Williams
2019-06-15 8:33 ` Christoph Hellwig
2019-06-15 8:33 ` Christoph Hellwig
2019-06-15 8:33 ` Christoph Hellwig
2019-06-15 18:09 ` Dan Williams
2019-06-15 18:09 ` Dan Williams
2019-06-15 18:09 ` Dan Williams
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