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Mon, 8 Jun 2020 04:41:16 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9442920825; Mon, 8 Jun 2020 04:41:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591591276; bh=J5h/VqF2fNIf2GrbFaLAXsQZNcYSt0W+Kxd/qNVxt7I=; h=Date:From:To:Subject:In-Reply-To:From; b=bXVeQsPEsEGLqmlh6oWD7X33de0v/JO5+0VePdrT86EN9RbcfFrvWD+1h8SVex3nc AAI9ShVVdoJD0/qO9momuqfxByrzOPI5PKIAsxu7n00Da907AO/gOQ/UJC+V+m4Q8J 0C3AJ+whRY1iSEezYw3/5k7Yn2phD2bw+63rVqIk= Date: Sun, 07 Jun 2020 21:41:15 -0700 From: Andrew Morton To: akpm@linux-foundation.org, corbet@lwn.net, david@fromorbit.com, jack@suse.cz, jasowang@redhat.com, jglisse@redhat.com, jhubbard@nvidia.com, jrdr.linux@gmail.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, mst@redhat.com, pankaj.gupta.linux@gmail.com, torvalds@linux-foundation.org, vbabka@suse.cz Subject: [patch 22/54] vhost: convert get_user_pages() --> pin_user_pages() Message-ID: <20200608044115.tMvGFNio5%akpm@linux-foundation.org> In-Reply-To: <20200607212615.b050e41fac139a1e16fe00bd@linux-foundation.org> User-Agent: s-nail v14.8.16 MIME-Version: 1.0 X-Rspamd-Queue-Id: 321351807EE23 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: John Hubbard Subject: vhost: convert get_user_pages() --> pin_user_pages() This code was using get_user_pages*(), in approximately a "Case 5" scenario (accessing the data within a page), using the categorization from [1]. That means that it's time to convert the get_user_pages*() + put_page() calls to pin_user_pages*() + unpin_user_pages() calls. There is some helpful background in [2]: basically, this is a small part of fixing a long-standing disconnect between pinning pages, and file systems' use of those pages. [1] Documentation/core-api/pin_user_pages.rst [2] "Explicit pinning of user-space pages": https://lwn.net/Articles/807108/ Link: http://lkml.kernel.org/r/20200529234309.484480-3-jhubbard@nvidia.com Signed-off-by: John Hubbard Reviewed-by: Jan Kara Acked-by: Michael S. Tsirkin Acked-by: Pankaj Gupta Cc: Jason Wang Cc: Dave Chinner Cc: Jérôme Glisse Cc: Jonathan Corbet Cc: Souptick Joarder Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- drivers/vhost/vhost.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) --- a/drivers/vhost/vhost.c~vhost-convert-get_user_pages-pin_user_pages +++ a/drivers/vhost/vhost.c @@ -1762,15 +1762,14 @@ static int set_bit_to_user(int nr, void int bit = nr + (log % PAGE_SIZE) * 8; int r; - r = get_user_pages_fast(log, 1, FOLL_WRITE, &page); + r = pin_user_pages_fast(log, 1, FOLL_WRITE, &page); if (r < 0) return r; BUG_ON(r != 1); base = kmap_atomic(page); set_bit(bit, base); kunmap_atomic(base); - set_page_dirty_lock(page); - put_page(page); + unpin_user_pages_dirty_lock(&page, 1, true); return 0; }