[PATCH v12 12/22] goldish_pipe: convert to pin_user_pages() and put_user_page()

From: John Hubbard <jhubbard@nvidia.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Michal Hocko" <mhocko@suse.com>, "Jan Kara" <jack@suse.cz>,
	kvm@vger.kernel.org, linux-doc@vger.kernel.org,
	"David Airlie" <airlied@linux.ie>,
	"Dave Chinner" <david@fromorbit.com>,
	dri-devel@lists.freedesktop.org,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mm@kvack.org, "Paul Mackerras" <paulus@samba.org>,
	linux-kselftest@vger.kernel.org,
	"Ira Weiny" <ira.weiny@intel.com>,
	"Jonathan Corbet" <corbet@lwn.net>,
	linux-rdma@vger.kernel.org,
	"Michael Ellerman" <mpe@ellerman.id.au>,
	"Christoph Hellwig" <hch@infradead.org>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	"Vlastimil Babka" <vbabka@suse.cz>,
	"Björn Töpel" <bjorn.topel@intel.com>,
	linux-media@vger.kernel.org, "Shuah Khan" <shuah@kernel.org>,
	"John Hubbard" <jhubbard@nvidia.com>,
	linux-block@vger.kernel.org, "Jérôme Glisse" <jglisse@redhat.com>,
	"Al Viro" <viro@zeniv.linux.org.uk>,
	"Kirill A . Shutemov" <kirill@shutemov.name>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Mauro Carvalho Chehab" <mchehab@kernel.org>,
	"Magnus Karlsson" <magnus.karlsson@intel.com>,
	"Jens Axboe" <axboe@kernel.dk>,
	netdev@vger.kernel.org,
	"Alex Williamson" <alex.williamson@redhat.com>,
	linux-fsdevel@vger.kernel.org, bpf@vger.kernel.org,
	linuxppc-dev@lists.ozlabs.org,
	"David S . Miller" <davem@davemloft.net>,
	"Mike Kravetz" <mike.kravetz@oracle.com>
Subject: [PATCH v12 12/22] goldish_pipe: convert to pin_user_pages() and put_user_page()
Date: Tue, 7 Jan 2020 14:45:48 -0800	[thread overview]
Message-ID: <20200107224558.2362728-13-jhubbard@nvidia.com> (raw)
In-Reply-To: <20200107224558.2362728-1-jhubbard@nvidia.com>

1. Call the new global pin_user_pages_fast(), from pin_goldfish_pages().

2. As required by pin_user_pages(), release these pages via
put_user_page(). In this case, do so via put_user_pages_dirty_lock().

That has the side effect of calling set_page_dirty_lock(), instead
of set_page_dirty(). This is probably more accurate.

As Christoph Hellwig put it, "set_page_dirty() is only safe if we are
dealing with a file backed page where we have reference on the inode it
hangs off." [1]

Another side effect is that the release code is simplified because
the page[] loop is now in gup.c instead of here, so just delete the
local release_user_pages() entirely, and call
put_user_pages_dirty_lock() directly, instead.

[1] https://lore.kernel.org/r/20190723153640.GB720@lst.de

Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/platform/goldfish/goldfish_pipe.c | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c
index ef50c264db71..2a5901efecde 100644
--- a/drivers/platform/goldfish/goldfish_pipe.c
+++ b/drivers/platform/goldfish/goldfish_pipe.c
@@ -274,7 +274,7 @@ static int goldfish_pin_pages(unsigned long first_page,
 		*iter_last_page_size = last_page_size;
 	}
 
-	ret = get_user_pages_fast(first_page, requested_pages,
+	ret = pin_user_pages_fast(first_page, requested_pages,
 				  !is_write ? FOLL_WRITE : 0,
 				  pages);
 	if (ret <= 0)
@@ -285,18 +285,6 @@ static int goldfish_pin_pages(unsigned long first_page,
 	return ret;
 }
 
-static void release_user_pages(struct page **pages, int pages_count,
-			       int is_write, s32 consumed_size)
-{
-	int i;
-
-	for (i = 0; i < pages_count; i++) {
-		if (!is_write && consumed_size > 0)
-			set_page_dirty(pages[i]);
-		put_page(pages[i]);
-	}
-}
-
 /* Populate the call parameters, merging adjacent pages together */
 static void populate_rw_params(struct page **pages,
 			       int pages_count,
@@ -372,7 +360,8 @@ static int transfer_max_buffers(struct goldfish_pipe *pipe,
 
 	*consumed_size = pipe->command_buffer->rw_params.consumed_size;
 
-	release_user_pages(pipe->pages, pages_count, is_write, *consumed_size);
+	put_user_pages_dirty_lock(pipe->pages, pages_count,
+				  !is_write && *consumed_size > 0);
 
 	mutex_unlock(&pipe->lock);
 	return 0;
-- 
2.24.1

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