Subject: linux-next: manual merge of the random tree with the mm-stable tree

From: Stephen Rothwell <[email-masked]>
Date: Tue, 9 Jul 2024 17:40:53 +1000

Hi all,

Today's linux-next merge of the random tree got a conflict in:

  mm/rmap.c

between commits:

  26d21b18d971 ("mm/rmap: remove duplicated exit code in pagewalk loop")
  15bde4abab73 ("mm: extend rmap flags arguments for folio_add_new_anon_rmap")

from the mm-stable tree and commit:

  94beef29e110 ("mm: add MAP_DROPPABLE for designating always lazily freeable mappings")

from the random tree.

I fixed it up (see below) and can carry the fix as necessary. This
is now fixed as far as linux-next is concerned, but any non trivial
conflicts should be mentioned to your upstream maintainer when your tree
is submitted for merging.  You may also want to consider cooperating
with the maintainer of the conflicting tree to minimise any particularly
complex conflicts.

-- 
Cheers,
Stephen Rothwell

diff --cc mm/rmap.c
index 8616308610b9,1f9b5a9cb121..000000000000
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@@ -1394,27 -1384,26 +1394,30 @@@ void folio_add_anon_rmap_pmd(struct fol
   *
   * Like folio_add_anon_rmap_*() but must only be called on *new* folios.
   * This means the inc-and-test can be bypassed.
 - * The folio does not have to be locked.
 + * The folio doesn't necessarily need to be locked while it's exclusive
 + * unless two threads map it concurrently. However, the folio must be
 + * locked if it's shared.
   *
 - * If the folio is pmd-mappable, it is accounted as a THP.  As the folio
 - * is new, it's assumed to be mapped exclusively by a single process.
 + * If the folio is pmd-mappable, it is accounted as a THP.
   */
  void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
 -		unsigned long address)
 +		unsigned long address, rmap_t flags)
  {
 -	int nr = folio_nr_pages(folio);
 +	const int nr = folio_nr_pages(folio);
 +	const bool exclusive = flags & RMAP_EXCLUSIVE;
 +	int nr_pmdmapped = 0;
  
  	VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);
 +	VM_WARN_ON_FOLIO(!exclusive && !folio_test_locked(folio), folio);
  	VM_BUG_ON_VMA(address < vma->vm_start ||
  			address + (nr << PAGE_SHIFT) > vma->vm_end, vma);
- 
- 	if (!folio_test_swapbacked(folio))
+ 	/*
+ 	 * VM_DROPPABLE mappings don't swap; instead they're just dropped when
+ 	 * under memory pressure.
+ 	 */
 -	if (!(vma->vm_flags & VM_DROPPABLE))
++	if (!folio_test_swapbacked(folio) && !(vma->vm_flags & VM_DROPPABLE))
  		__folio_set_swapbacked(folio);
 -	__folio_set_anon(folio, vma, address, true);
 +	__folio_set_anon(folio, vma, address, exclusive);
  
  	if (likely(!folio_test_large(folio))) {
  		/* increment count (starts at -1) */
@@@ -1858,8 -1862,15 +1867,13 @@@ static bool try_to_unmap_one(struct fol
  				 * discarded. Remap the page to page table.
  				 */
  				set_pte_at(mm, address, pvmw.pte, pteval);
- 				folio_set_swapbacked(folio);
+ 				/*
+ 				 * Unlike MADV_FREE mappings, VM_DROPPABLE ones
+ 				 * never get swap backed on failure to drop.
+ 				 */
+ 				if (!(vma->vm_flags & VM_DROPPABLE))
+ 					folio_set_swapbacked(folio);
 -				ret = false;
 -				page_vma_mapped_walk_done(&pvmw);
 -				break;
 +				goto walk_abort;
  			}
  
  			if (swap_duplicate(entry) < 0) {