mm/rmap: drop "compound" parameter from page_add_new_anon_rmap()

New anonymous pages are always mapped natively: only THP/khugepaged code
maps a new compound anonymous page and passes "true".  Otherwise, we're
just dealing with simple, non-compound pages.

Let's give the interface clearer semantics and document these.  Remove the
PageTransCompound() sanity check from page_add_new_anon_rmap().

Link: https://lkml.kernel.org/r/20220428083441.37290-9-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Khalid Aziz <khalid.aziz@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Liang Zhang <zhangliang5@huawei.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Oded Gabbay <oded.gabbay@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pedro Demarchi Gomes <pedrodemargomes@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 6 insertions, 5 deletions

diff --git a/mm/rmap.c b/mm/rmap.c
index 32630f1b1ee1..90f92c53476f 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1226,19 +1226,22 @@ void page_add_anon_rmap(struct page *page,
 }
 
 /**
- * page_add_new_anon_rmap - add pte mapping to a new anonymous page
+ * page_add_new_anon_rmap - add mapping to a new anonymous page
  * @page:	the page to add the mapping to
  * @vma:	the vm area in which the mapping is added
  * @address:	the user virtual address mapped
- * @compound:	charge the page as compound or small page
+ *
+ * If it's a compound page, it is accounted as a compound page. As the page
+ * is new, it's assume to get mapped exclusively by a single process.
  *
  * Same as page_add_anon_rmap but must only be called on *new* pages.
  * This means the inc-and-test can be bypassed.
  * Page does not have to be locked.
  */
 void page_add_new_anon_rmap(struct page *page,
-	struct vm_area_struct *vma, unsigned long address, bool compound)
+	struct vm_area_struct *vma, unsigned long address)
 {
+	const bool compound = PageCompound(page);
 	int nr = compound ? thp_nr_pages(page) : 1;
 
 	VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
@@ -1251,8 +1254,6 @@ void page_add_new_anon_rmap(struct page *page,
 
 		__mod_lruvec_page_state(page, NR_ANON_THPS, nr);
 	} else {
-		/* Anon THP always mapped first with PMD */
-		VM_BUG_ON_PAGE(PageTransCompound(page), page);
 		/* increment count (starts at -1) */
 		atomic_set(&page->_mapcount, 0);
 	}