mm/munlock: rmap call mlock_vma_page() munlock_vma_page()

Add vma argument to mlock_vma_page() and munlock_vma_page(), make them
inline functions which check (vma->vm_flags & VM_LOCKED) before calling
mlock_page() and munlock_page() in mm/mlock.c.

Add bool compound to mlock_vma_page() and munlock_vma_page(): this is
because we have understandable difficulty in accounting pte maps of THPs,
and if passed a PageHead page, mlock_page() and munlock_page() cannot
tell whether it's a pmd map to be counted or a pte map to be ignored.

Add vma arg to page_add_file_rmap() and page_remove_rmap(), like the
others, and use that to call mlock_vma_page() at the end of the page
adds, and munlock_vma_page() at the end of page_remove_rmap() (end or
beginning? unimportant, but end was easier for assertions in testing).

No page lock is required (although almost all adds happen to hold it):
delete the "Serialize with page migration" BUG_ON(!PageLocked(page))s.
Certainly page lock did serialize with page migration, but I'm having
difficulty explaining why that was ever important.

Mlock accounting on THPs has been hard to define, differed between anon
and file, involved PageDoubleMap in some places and not others, required
clear_page_mlock() at some points.  Keep it simple now: just count the
pmds and ignore the ptes, there is no reason for ptes to undo pmd mlocks.

page_add_new_anon_rmap() callers unchanged: they have long been calling
lru_cache_add_inactive_or_unevictable(), which does its own VM_LOCKED
handling (it also checks for not VM_SPECIAL: I think that's overcautious,
and inconsistent with other checks, that mmap_region() already prevents
VM_LOCKED on VM_SPECIAL; but haven't quite convinced myself to change it).

Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

1 files changed, 9 insertions, 8 deletions

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index dc48aa8c2c94..ac29b076082b 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -167,18 +167,19 @@ struct anon_vma *page_get_anon_vma(struct page *page);
  */
 void page_move_anon_rmap(struct page *, struct vm_area_struct *);
 void page_add_anon_rmap(struct page *, struct vm_area_struct *,
-		unsigned long, bool);
+		unsigned long address, bool compound);
 void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
-			   unsigned long, int);
+		unsigned long address, int flags);
 void page_add_new_anon_rmap(struct page *, struct vm_area_struct *,
-		unsigned long, bool);
-void page_add_file_rmap(struct page *, bool);
-void page_remove_rmap(struct page *, bool);
-
+		unsigned long address, bool compound);
+void page_add_file_rmap(struct page *, struct vm_area_struct *,
+		bool compound);
+void page_remove_rmap(struct page *, struct vm_area_struct *,
+		bool compound);
 void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
-			    unsigned long);
+		unsigned long address);
 void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
-				unsigned long);
+		unsigned long address);
 
 static inline void page_dup_rmap(struct page *page, bool compound)
 {