[PATCH v3 2/3] mm/gup: small refactoring: simplify try_grab_page()

From: John Hubbard
Date: Fri Aug 13 2021 - 00:41:47 EST


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.

Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
---
include/linux/mm.h | 4 ++--
mm/gup.c | 35 +++++------------------------------
2 files changed, 7 insertions(+), 32 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index ce8fc0fd6d6e..ba985eaf3f19 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1204,8 +1204,8 @@ 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 52f08e3177e9..886d6148d3d0 100644
--- 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);
}

/**
--
2.32.0