On 11/18/19 1:46 AM, Jan Kara wrote:

On Thu 14-11-19 21:53:18, John Hubbard wrote:

quoted

There are four locations in gup.c that have a fair amount of code
duplication. This means that changing one requires making the same
changes in four places, not to mention reading the same code four
times, and wondering if there are subtle differences.

Factor out the common code into static functions, thus reducing the
overall line count and the code's complexity.

Also, take the opportunity to slightly improve the efficiency of the
error cases, by doing a mass subtraction of the refcount, surrounded
by get_page()/put_page().

Also, further simplify (slightly), by waiting until the the successful
end of each routine, to increment *nr.

Reviewed-by: Jérôme Glisse <redacted>
Cc: Jan Kara <jack@suse.cz>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Aneesh Kumar K.V <redacted>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 mm/gup.c | 95 ++++++++++++++++++++++++--------------------------------
 1 file changed, 40 insertions(+), 55 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 85caf76b3012..858541ea30ce 100644
--- a/mm/gup.c
+++ b/mm/gup.c

@@ -1969,6 +1969,29 @@ static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
 }
 #endif
 
+static int __record_subpages(struct page *page, unsigned long addr,
+			     unsigned long end, struct page **pages)
+{
+	int nr = 0;
+	int nr_recorded_pages = 0;
+
+	do {
+		pages[nr] = page;
+		nr++;
+		page++;
+		nr_recorded_pages++;
+	} while (addr += PAGE_SIZE, addr != end);
+	return nr_recorded_pages;

nr == nr_recorded_pages so no need for both... BTW, structuring this as a
for loop would be probably more logical and shorter now:

	for (nr = 0; addr != end; addr += PAGE_SIZE)
		pages[nr++] = page++;
	return nr;

Nice touch, I've applied it.

thanks,
-- 
John Hubbard
NVIDIA

The rest of the patch looks good to me.

								Honza