mm: add support for releasing multiple instances of a page

Add a function that allows us to batch free a page that has multiple
references outstanding.  Specifically this function can be used to drop
a page being used in the page frag alloc cache.  With this drivers can
make use of functionality similar to the page frag alloc cache without
having to do any workarounds for the fact that there is no function that
frees multiple references.

Link: http://lkml.kernel.org/r/20161110113606.76501.70752.stgit@ahduyck-blue-test.jf.intel.com
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Hans-Christian Noren Egtvedt <egtvedt@samfundet.no>
Cc: Helge Deller <deller@gmx.de>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Keguang Zhang <keguang.zhang@gmail.com>
Cc: Ley Foon Tan <lftan@altera.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Steven Miao <realmz6@gmail.com>
Cc: Tobias Klauser <tklauser@distanz.ch>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index f8041f9de31efc998916537889dd559b9fc375cb..4175dca4ac39dd7848e3abcda5eb163865ab2734 100644 (file)
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -506,6 +506,8 @@ extern void free_hot_cold_page(struct page *page, bool cold);
 extern void free_hot_cold_page_list(struct list_head *list, bool cold);
 
 struct page_frag_cache;
+extern void __page_frag_drain(struct page *page, unsigned int order,
+                             unsigned int count);
 extern void *__alloc_page_frag(struct page_frag_cache *nc,
                               unsigned int fragsz, gfp_t gfp_mask);
 extern void __free_page_frag(void *addr);

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f64e7bcb43b7c8666f883bf2f5a506d4d990b536..2c6d5f64feca409e9fdca4b551a240882e421476 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3925,6 +3925,20 @@ static struct page *__page_frag_refill(struct page_frag_cache *nc,
        return page;
 }
 
+void __page_frag_drain(struct page *page, unsigned int order,
+                      unsigned int count)
+{
+       VM_BUG_ON_PAGE(page_ref_count(page) == 0, page);
+
+       if (page_ref_sub_and_test(page, count)) {
+               if (order == 0)
+                       free_hot_cold_page(page, false);
+               else
+                       __free_pages_ok(page, order);
+       }
+}
+EXPORT_SYMBOL(__page_frag_drain);
+
 void *__alloc_page_frag(struct page_frag_cache *nc,
                        unsigned int fragsz, gfp_t gfp_mask)
 {