[PATCH v6 11/24] goldish_pipe: convert to pin_user_pages() and put_user_page()

John Hubbard
2019-11-19T08:19:13Z

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 7ed2a21a0bac..635a8bc1b480 100644
--- a/drivers/platform/goldfish/goldfish_pipe.c
+++ b/drivers/platform/goldfish/goldfish_pipe.c
@@ -274,7 +274,7 @@ static int pin_goldfish_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 pin_goldfish_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;
--
2.24.0