On 9/1/25 8:03 AM, David Hildenbrand wrote:
We can just cleanup the code by calculating the #refs earlier, so we can just inline what remains of record_subpages().
Calculate the number of references/pages ahead of times, and record them only once all our tests passed.
Signed-off-by: David Hildenbrand david@redhat.com
mm/gup.c | 25 ++++++++----------------- 1 file changed, 8 insertions(+), 17 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c index c10cd969c1a3b..f0f4d1a68e094 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -484,19 +484,6 @@ static inline void mm_set_has_pinned_flag(struct mm_struct *mm) #ifdef CONFIG_MMU #ifdef CONFIG_HAVE_GUP_FAST -static int record_subpages(struct page *page, unsigned long sz,
unsigned long addr, unsigned long end,struct page **pages)-{
- int nr;
- page += (addr & (sz - 1)) >> PAGE_SHIFT;
- for (nr = 0; addr != end; nr++, addr += PAGE_SIZE)
pages[nr] = page++;- return nr;
-}
/**
- try_grab_folio_fast() - Attempt to get or pin a folio in fast path.
- @page: pointer to page to be grabbed
@@ -2967,8 +2954,8 @@ static int gup_fast_pmd_leaf(pmd_t orig, pmd_t *pmdp, unsigned long addr, if (pmd_special(orig)) return 0;
- page = pmd_page(orig);
- refs = record_subpages(page, PMD_SIZE, addr, end, pages + *nr);
- refs = (end - addr) >> PAGE_SHIFT;
- page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
folio = try_grab_folio_fast(page, refs, flags); if (!folio) @@ -2989,6 +2976,8 @@ static int gup_fast_pmd_leaf(pmd_t orig, pmd_t *pmdp, unsigned long addr, } *nr += refs;
- for (; refs; refs--)
*(pages++) = page++;} @@ -3007,8 +2996,8 @@ static int gup_fast_pud_leaf(pud_t orig, pud_t *pudp, unsigned long addr, if (pud_special(orig)) return 0;
- page = pud_page(orig);
- refs = record_subpages(page, PUD_SIZE, addr, end, pages + *nr);
- refs = (end - addr) >> PAGE_SHIFT;
- page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
folio = try_grab_folio_fast(page, refs, flags); if (!folio) @@ -3030,6 +3019,8 @@ static int gup_fast_pud_leaf(pud_t orig, pud_t *pudp, unsigned long addr, } *nr += refs;
- for (; refs; refs--)
*(pages++) = page++;
Hi David,
Probably a similar sentiment as Lorenzo here...the above diffs make the code *worse* to read. In fact, I recall adding record_subpages() here long ago, specifically to help clarify what was going on.
Now it's been returned to it's original, cryptic form.
Just my take on it, for whatever that's worth. :)
thanks,