lkml.org 
[lkml]   [2019]   [Nov]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v5 02/24] mm/gup: factor out duplicate code from four routines
On Thu 14-11-19 21:53:18, John Hubbard wrote:
> 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 <jglisse@redhat.com>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Ira Weiny <ira.weiny@intel.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> 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;

The rest of the patch looks good to me.

Honza

--
Jan Kara <jack@suse.com>
SUSE Labs, CR

\
 
 \ /
  Last update: 2019-11-18 13:03    [W:0.183 / U:4.668 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site