From: Jason Gunthorpe <jgg@ziepe.ca>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-mm@kvack.org, linux-nvdimm@lists.01.org,
Christoph Hellwig <hch@lst.de>,
Shiyang Ruan <ruansy.fnst@fujitsu.com>,
Vishal Verma <vishal.l.verma@intel.com>,
Dave Jiang <dave.jiang@intel.com>,
Ira Weiny <ira.weiny@intel.com>,
Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
david@fromorbit.com, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] mm/devmap: Remove pgmap accounting in the get_user_pages_fast() path
Date: Thu, 25 Mar 2021 11:37:30 -0300 [thread overview]
Message-ID: <20210325143730.GL2710221@ziepe.ca> (raw)
In-Reply-To: <161604050866.1463742.7759521510383551055.stgit@dwillia2-desk3.amr.corp.intel.com>
On Wed, Mar 17, 2021 at 09:08:28PM -0700, Dan Williams wrote:
> Now that device-dax and filesystem-dax are guaranteed to unmap all user
> mappings of devmap / DAX pages before tearing down the 'struct page'
> array, get_user_pages_fast() can rely on its traditional synchronization
> method "validate_pte(); get_page(); revalidate_pte()" to catch races with
> device shutdown. Specifically the unmap guarantee ensures that gup-fast
> either succeeds in taking a page reference (lock-less), or it detects a
> need to fall back to the slow path where the device presence can be
> revalidated with locks held.
>
> Reported-by: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Shiyang Ruan <ruansy.fnst@fujitsu.com>
> Cc: Vishal Verma <vishal.l.verma@intel.com>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Ira Weiny <ira.weiny@intel.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
> mm/gup.c | 38 ++++++++++++++++----------------------
> 1 file changed, 16 insertions(+), 22 deletions(-)
I'm happy to see this, and it is really the right thing that PTEs are
properly removed before anything happens to the pages under them.
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Jason
next prev parent reply other threads:[~2021-03-25 14:38 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-18 4:08 [PATCH 0/3] mm, pmem: Force unmap pmem on surprise remove Dan Williams
2021-03-18 4:08 ` [PATCH 1/3] mm/memory-failure: Prepare for mass memory_failure() Dan Williams
2021-03-18 4:08 ` [PATCH 2/3] mm, dax, pmem: Introduce dev_pagemap_failure() Dan Williams
2021-03-18 4:45 ` Darrick J. Wong
2021-03-18 19:26 ` Dan Williams
2021-03-18 4:57 ` Dave Chinner
2021-03-18 19:20 ` Dan Williams
2021-03-20 1:46 ` Dave Chinner
2021-03-20 2:39 ` Dan Williams
2021-03-18 4:08 ` [PATCH 3/3] mm/devmap: Remove pgmap accounting in the get_user_pages_fast() path Dan Williams
2021-03-18 10:00 ` Joao Martins
2021-03-18 17:03 ` Dan Williams
2021-03-25 14:34 ` Jason Gunthorpe
2021-03-29 23:24 ` Dan Williams
2021-03-30 13:49 ` Jason Gunthorpe
2021-03-24 17:45 ` Dan Williams
2021-03-24 19:00 ` Joao Martins
2021-04-01 19:54 ` Joao Martins
2021-03-25 14:37 ` Jason Gunthorpe [this message]
2021-03-25 13:02 ` [PATCH 0/3] mm, pmem: Force unmap pmem on surprise remove David Hildenbrand
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