From: Jason Gunthorpe <jgg@ziepe.ca>
To: ira.weiny@intel.com
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
"Michal Hocko" <mhocko@suse.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
"Jérôme Glisse" <jglisse@redhat.com>,
"Dan Williams" <dan.j.williams@intel.com>,
"John Hubbard" <jhubbard@nvidia.com>
Subject: Re: [PATCH v4] mm/swap: Fix release_pages() when releasing devmap pages
Date: Tue, 2 Jul 2019 22:15:22 -0300 [thread overview]
Message-ID: <20190703011522.GA15993@ziepe.ca> (raw)
In-Reply-To: <20190605214922.17684-1-ira.weiny@intel.com>
On Wed, Jun 05, 2019 at 02:49:22PM -0700, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
>
> release_pages() is an optimized version of a loop around put_page().
> Unfortunately for devmap pages the logic is not entirely correct in
> release_pages(). This is because device pages can be more than type
> MEMORY_DEVICE_PUBLIC. There are in fact 4 types, private, public, FS
> DAX, and PCI P2PDMA. Some of these have specific needs to "put" the
> page while others do not.
>
> This logic to handle any special needs is contained in
> put_devmap_managed_page(). Therefore all devmap pages should be
> processed by this function where we can contain the correct logic for a
> page put.
>
> Handle all device type pages within release_pages() by calling
> put_devmap_managed_page() on all devmap pages. If
> put_devmap_managed_page() returns true the page has been put and we
> continue with the next page. A false return of
> put_devmap_managed_page() means the page did not require special
> processing and should fall to "normal" processing.
>
> This was found via code inspection while determining if release_pages()
> and the new put_user_pages() could be interchangeable.[1]
>
> [1] https://lore.kernel.org/lkml/20190523172852.GA27175@iweiny-DESK2.sc.intel.com/
>
> Cc: Jérôme Glisse <jglisse@redhat.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> Reviewed-by: John Hubbard <jhubbard@nvidia.com>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
>
> ---
> Changes from V3:
> Update comment to the one provided by John
>
> Changes from V2:
> Update changelog for more clarity as requested by Michal
> Update comment WRT "failing" of put_devmap_managed_page()
>
> Changes from V1:
> Add comment clarifying that put_devmap_managed_page() can still
> fail.
> Add Reviewed-by tags.
>
> mm/swap.c | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
Andrew,
As per the discussion on the hmm thread I took this patch into the
hmm.git as the conflict that was created with CH's rework was tricky -
the resolution is simple, but keeping Ira's hunk instead of the delete
is, IMHO, subtle.
Regards,
Jason
prev parent reply other threads:[~2019-07-03 1:15 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-05 21:49 [PATCH v4] mm/swap: Fix release_pages() when releasing devmap pages ira.weiny
2019-06-21 8:11 ` Michal Hocko
2019-07-03 1:15 ` Jason Gunthorpe [this message]
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