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video: fbdev: convert get_user_pages() --> pin_user_pages()

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This code was using get_user_pages*(), in a "Case 2" scenario
(DMA/RDMA), 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: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Gustavo A. R. Silva <gustavo@embeddedor.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-fbdev@vger.kernel.org
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200522041506.39638-3-jhubbard@nvidia.com
This commit is contained in:
John Hubbard 2020-05-21 21:15:06 -07:00 committed by Sam Ravnborg
parent e2e1c7bda4
commit 84be242dae
1 changed files with 2 additions and 4 deletions
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6
drivers/video/fbdev/pvr2fb.c
View File

@ -652,7 +652,7 @@ static ssize_t pvr2fb_write(struct fb_info *info, const char *buf,
if (!pages)
return -ENOMEM;
ret = get_user_pages_fast((unsigned long)buf, nr_pages, FOLL_WRITE, pages);
ret = pin_user_pages_fast((unsigned long)buf, nr_pages, FOLL_WRITE, pages);
if (ret < nr_pages) {
if (ret < 0) {
/*
@ -712,9 +712,7 @@ out:
ret = count;
out_unmap:
for (i = 0; i < nr_pages; i++)
put_page(pages[i]);
unpin_user_pages(pages, nr_pages);
kfree(pages);
return ret;