[074/212] mm/gup: small refactoring: simplify try_grab_page()

Commit Message

Andrew Morton Sept. 2, 2021, 9:53 p.m. UTC

From: John Hubbard <[e-mail]>
Subject: mm/gup: small refactoring: simplify try_grab_page()

try_grab_page() does the same thing as try_grab_compound_head(..., refs=1,
...), just with a different API.  So there is a lot of code duplication
there.

Change try_grab_page() to call try_grab_compound_head(), while keeping the
API contract identical for callers.

Also, now that try_grab_compound_head() always has a caller, remove the
__maybe_unused annotation.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: John Hubbard <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Cc: Matthew Wilcox <[e-mail]>
Cc: Christian Borntraeger <[e-mail]>
Cc: Heiko Carstens <[e-mail]>
Cc: Vasily Gorbik <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 include/linux/mm.h |    4 ++--
 mm/gup.c           |   35 +++++------------------------------
 2 files changed, 7 insertions(+), 32 deletions(-)

Patch

--- a/include/linux/mm.h~mm-gup-small-refactoring-simplify-try_grab_page
+++ a/include/linux/mm.h
@@ -1214,8 +1214,8 @@  static inline void get_page(struct page
 }
 
 bool __must_check try_grab_page(struct page *page, unsigned int flags);
-__maybe_unused struct page *try_grab_compound_head(struct page *page, int refs,
-						   unsigned int flags);
+struct page *try_grab_compound_head(struct page *page, int refs,
+				    unsigned int flags);
 
 
 static inline __must_check bool try_get_page(struct page *page)
--- a/mm/gup.c~mm-gup-small-refactoring-simplify-try_grab_page
+++ a/mm/gup.c
@@ -124,8 +124,8 @@  static inline struct page *try_get_compo
  * considered failure, and furthermore, a likely bug in the caller, so a warning
  * is also emitted.
  */
-__maybe_unused struct page *try_grab_compound_head(struct page *page,
-						   int refs, unsigned int flags)
+struct page *try_grab_compound_head(struct page *page,
+				    int refs, unsigned int flags)
 {
 	if (flags & FOLL_GET)
 		return try_get_compound_head(page, refs);
@@ -208,35 +208,10 @@  static void put_compound_head(struct pag
  */
 bool __must_check try_grab_page(struct page *page, unsigned int flags)
 {
-	WARN_ON_ONCE((flags & (FOLL_GET | FOLL_PIN)) == (FOLL_GET | FOLL_PIN));
+	if (!(flags & (FOLL_GET | FOLL_PIN)))
+		return true;
 
-	if (flags & FOLL_GET)
-		return try_get_page(page);
-	else if (flags & FOLL_PIN) {
-		int refs = 1;
-
-		page = compound_head(page);
-
-		if (WARN_ON_ONCE(page_ref_count(page) <= 0))
-			return false;
-
-		if (hpage_pincount_available(page))
-			hpage_pincount_add(page, 1);
-		else
-			refs = GUP_PIN_COUNTING_BIAS;
-
-		/*
-		 * Similar to try_grab_compound_head(): even if using the
-		 * hpage_pincount_add/_sub() routines, be sure to
-		 * *also* increment the normal page refcount field at least
-		 * once, so that the page really is pinned.
-		 */
-		page_ref_add(page, refs);
-
-		mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_ACQUIRED, 1);
-	}
-
-	return true;
+	return try_grab_compound_head(page, 1, flags);
 }
 
 /**