> > From: Barry Song <v-songbaohua@xxxxxxxx> > > In the case of a swap-in, a new anonymous folio is not necessarily > exclusive. This patch updates the rmap flags to allow a new anonymous > folio to be treated as either exclusive or non-exclusive. To maintain > the existing behavior, we always use EXCLUSIVE as the default setting. > > Suggested-by: David Hildenbrand <david@xxxxxxxxxx> > Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx> > Tested-by: Shuai Yuan <yuanshuai@xxxxxxxx> > --- Hi Andrew, Could you please help squash the following change (a documentation enhancement suggested by David) into this patch? From: Barry Song <v-songbaohua@xxxxxxxx> Date: Sat, 22 Jun 2024 14:51:38 +1200 Subject: [PATCH] mm: enhence doc for extend rmap flags arguments for folio_add_new_anon_rmap Suggested-by: David Hildenbrand <david@xxxxxxxxxx> Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx> --- mm/rmap.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/rmap.c b/mm/rmap.c index df1a43295c85..9a8d9c848168 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1394,7 +1394,9 @@ void folio_add_anon_rmap_pmd(struct folio *folio, struct page *page, * * 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. */ @@ -1406,6 +1408,7 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma, 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); __folio_set_swapbacked(folio); -- 2.34.1
