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Tsirkin" , Jason Wang , Vlastimil Babka , =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= , Jan Kara , Dave Chinner , Souptick Joarder , Jonathan Corbet , , , , , , LKML , , John Hubbard Subject: [PATCH v2 2/2] vhost: convert get_user_pages() --> pin_user_pages() Date: Sun, 31 May 2020 22:26:33 -0700 Message-ID: <20200601052633.853874-3-jhubbard@nvidia.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200601052633.853874-1-jhubbard@nvidia.com> References: <20200601052633.853874-1-jhubbard@nvidia.com> MIME-Version: 1.0 X-NVConfidentiality: public Content-Transfer-Encoding: quoted-printable Content-Type: text/plain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1590989188; bh=w393fB7aMdfV2Mn/9DhXAANTn2k/9wVRvrXDZ4wAcPA=; h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:X-NVConfidentiality: Content-Transfer-Encoding:Content-Type; b=ZvXUZSFSzSw1/mLTCiIZR8aixUJ+vnWFQT0TJOASKXrExwHg1C1RKAI8xNztpLx0h RNahukkHX+PKzIflSyIGAHeUzSdLSKBxn86977TkIfrxV4kTdKpB1Lry94r3aXUkUp P8tE0nSKkUCakFEvxZoasInFCaJuGWUV0d8azWn6FsjAg3vecq6M9gVbfsgbKyPuYB 67MMhjIuEWXDTXt5/U9zgSgK8ja5jyW9b75gdqwiIG07b9tCmc0/iK3wmd+lgpV0NS dsNoLaKm5gqPfL3JZiCeRSx/B0Crepd6BB/BrWfOPC3qapoq5GPDPX4c8zTToMyv94 5DIvXQO/TYFvA== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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/ Cc: Michael S. Tsirkin Cc: Jason Wang Cc: kvm@vger.kernel.org Cc: virtualization@lists.linux-foundation.org Cc: netdev@vger.kernel.org Signed-off-by: John Hubbard --- drivers/vhost/vhost.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 21a59b598ed8..596132a96cd5 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1762,15 +1762,14 @@ static int set_bit_to_user(int nr, void __user *add= r) int bit =3D nr + (log % PAGE_SIZE) * 8; int r; =20 - r =3D get_user_pages_fast(log, 1, FOLL_WRITE, &page); + r =3D pin_user_pages_fast(log, 1, FOLL_WRITE, &page); if (r < 0) return r; BUG_ON(r !=3D 1); base =3D 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; } =20 --=20 2.26.2