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/20210813044133.1536842-3-jhubbard@nvidia.com
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7ca22e6..af4845e 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1214,8 +1214,8 @@ static inline void get_page(struct page *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)

diff --git a/mm/gup.c b/mm/gup.c
index 26ce6bb..d60419e 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -124,8 +124,8 @@ static inline struct page *try_get_compound_head(struct page *page, int refs)
  * 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 page *page, int refs, unsigned int flags)
  */
 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);
 }
 
 /**