Messages in this thread | | | Subject | Re: [PATCH v4 02/23] mm/gup: factor out duplicate code from four routines | From | John Hubbard <> | Date | Wed, 13 Nov 2019 15:12:02 -0800 |
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On 11/13/19 3:15 AM, Jan Kara wrote: > On Tue 12-11-19 20:26:49, 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: 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> > >> diff --git a/mm/gup.c b/mm/gup.c >> index 85caf76b3012..199da99e8ffc 100644 >> --- a/mm/gup.c >> +++ b/mm/gup.c >> @@ -1969,6 +1969,34 @@ 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) >> +{ >> + int nr_recorded_pages = 0; >> + >> + do { >> + pages[nr] = page; >> + nr++; >> + page++; >> + nr_recorded_pages++; >> + } while (addr += PAGE_SIZE, addr != end); >> + return nr_recorded_pages; >> +} > > Why don't you pass in already pages + nr?
Aha, that does save a function argument. Will do.
... >> +static void __huge_pt_done(struct page *head, int nr_recorded_pages, int *nr) >> +{ >> + *nr += nr_recorded_pages; >> + SetPageReferenced(head); >> +} > > I don't find this last helper very useful. It seems to muddy water more > than necessary...
Yes, I suspect it's rather unloved, and the fact that it was hard to accurately name should have been a big hint to not do it. I'll remove the helper and put the lines back in directly.
thanks, -- John Hubbard NVIDIA
> > Other than that the cleanup looks nice to me. > > Honza >
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