tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   1eb586a9782cde8e5091b9de74603e0a8386b09e
commit: ee3fe497bdf0c7cb6fbec346f36aa1f9b1dfe6dd [9137/9689] mm: gup: do not call try_grab_folio() in slow path
config: powerpc-randconfig-r005-20221108
compiler: powerpc-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build):

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202406290729.21FzkVlI-lkp@intel.com/

All error/warnings (new ones prefixed by >>):

   mm/gup.c: In function 'gup_hugepte':
>> mm/gup.c:476:25: error: implicit declaration of function 'try_grab_folio_fast'; did you mean 'try_grab_folio'? [-Werror=implicit-function-declaration]
     476 |                 folio = try_grab_folio_fast(page, refs, flags);
         |                         ^~~~~~~~~~~~~~~~~~~
         |                         try_grab_folio
>> mm/gup.c:476:23: warning: assignment to 'struct folio *' from 'int' makes pointer from integer without a cast [-Wint-conversion]
     476 |                 folio = try_grab_folio_fast(page, refs, flags);
         |                       ^
   mm/gup.c: At top level:
>> mm/gup.c:2748:22: error: conflicting types for 'try_grab_folio_fast'; have 'struct folio *(struct page *, int,  unsigned int)'
    2748 | static struct folio *try_grab_folio_fast(struct page *page, int refs,
         |                      ^~~~~~~~~~~~~~~~~~~
   mm/gup.c:476:25: note: previous implicit declaration of 'try_grab_folio_fast' with type 'int()'
     476 |                 folio = try_grab_folio_fast(page, refs, flags);
         |                         ^~~~~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors


vim +476 mm/gup.c

   441	
   442	/*
   443	 * Returns 1 if succeeded, 0 if failed, -EMLINK if unshare needed.
   444	 *
   445	 * NOTE: for the same entry, gup-fast and gup-slow can return different
   446	 * results (0 v.s. -EMLINK) depending on whether vma is available.  This is
   447	 * the expected behavior, where we simply want gup-fast to fallback to
   448	 * gup-slow to take the vma reference first.
   449	 */
   450	static int gup_hugepte(struct vm_area_struct *vma, pte_t *ptep, unsigned long sz,
   451			       unsigned long addr, unsigned long end, unsigned int flags,
   452			       struct page **pages, int *nr, bool fast)
   453	{
   454		unsigned long pte_end;
   455		struct page *page;
   456		struct folio *folio;
   457		pte_t pte;
   458		int refs;
   459	
   460		pte_end = (addr + sz) & ~(sz-1);
   461		if (pte_end < end)
   462			end = pte_end;
   463	
   464		pte = huge_ptep_get(ptep);
   465	
   466		if (!pte_access_permitted(pte, flags & FOLL_WRITE))
   467			return 0;
   468	
   469		/* hugepages are never "special" */
   470		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
   471	
   472		page = pte_page(pte);
   473		refs = record_subpages(page, sz, addr, end, pages + *nr);
   474	
   475		if (fast) {
 > 476			folio = try_grab_folio_fast(page, refs, flags);
   477			if (!folio)
   478				return 0;
   479		} else {
   480			folio = page_folio(page);
   481			if (try_grab_folio(folio, refs, flags))
   482				return 0;
   483		}
   484	
   485		if (unlikely(pte_val(pte) != pte_val(ptep_get(ptep)))) {
   486			gup_put_folio(folio, refs, flags);
   487			return 0;
   488		}
   489	
   490		if (!pte_write(pte) && gup_must_unshare(vma, flags, &folio->page)) {
   491			gup_put_folio(folio, refs, flags);
   492			return -EMLINK;
   493		}
   494	
   495		*nr += refs;
   496		folio_set_referenced(folio);
   497		return 1;
   498	}
   499	

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