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From: Alexander Duyck <alexander.h.duyck@intel.com>
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Date: Wed, 14 Dec 2016 15:05:26 -0800
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Subject: [PATCH] mm: add support for releasing multiple instances of a page
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Add a function that allows us to batch free a page that has multiple
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references outstanding. Specifically this function can be used to drop
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a page being used in the page frag alloc cache. With this drivers can
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make use of functionality similar to the page frag alloc cache without
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having to do any workarounds for the fact that there is no function that
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frees multiple references.
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Link: http://lkml.kernel.org/r/20161110113606.76501.70752.stgit@ahduyck-blue-test.jf.intel.com
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Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
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Cc: "David S. Miller" <davem@davemloft.net>
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Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
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Cc: Chris Metcalf <cmetcalf@mellanox.com>
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Cc: David Howells <dhowells@redhat.com>
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Cc: Geert Uytterhoeven <geert@linux-m68k.org>
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Cc: Hans-Christian Noren Egtvedt <egtvedt@samfundet.no>
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Cc: Helge Deller <deller@gmx.de>
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Cc: James Hogan <james.hogan@imgtec.com>
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Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
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Cc: Jonas Bonn <jonas@southpole.se>
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Cc: Keguang Zhang <keguang.zhang@gmail.com>
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Cc: Ley Foon Tan <lftan@altera.com>
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Cc: Mark Salter <msalter@redhat.com>
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Cc: Max Filippov <jcmvbkbc@gmail.com>
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Cc: Michael Ellerman <mpe@ellerman.id.au>
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Cc: Michal Simek <monstr@monstr.eu>
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Cc: Ralf Baechle <ralf@linux-mips.org>
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Cc: Rich Felker <dalias@libc.org>
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Cc: Richard Kuo <rkuo@codeaurora.org>
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Cc: Russell King <linux@armlinux.org.uk>
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Cc: Steven Miao <realmz6@gmail.com>
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Cc: Tobias Klauser <tklauser@distanz.ch>
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Cc: Vineet Gupta <vgupta@synopsys.com>
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Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
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Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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---
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--- a/include/linux/gfp.h
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+++ b/include/linux/gfp.h
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@@ -506,6 +506,8 @@ extern void free_hot_cold_page(struct pa
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extern void free_hot_cold_page_list(struct list_head *list, bool cold);
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struct page_frag_cache;
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+extern void __page_frag_drain(struct page *page, unsigned int order,
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+ unsigned int count);
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extern void *__alloc_page_frag(struct page_frag_cache *nc,
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unsigned int fragsz, gfp_t gfp_mask);
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extern void __free_page_frag(void *addr);
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--- a/mm/page_alloc.c
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+++ b/mm/page_alloc.c
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@@ -3945,6 +3945,20 @@ static struct page *__page_frag_refill(s
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return page;
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}
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+void __page_frag_drain(struct page *page, unsigned int order,
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+ unsigned int count)
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+{
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+ VM_BUG_ON_PAGE(page_ref_count(page) == 0, page);
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+
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+ if (page_ref_sub_and_test(page, count)) {
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+ if (order == 0)
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+ free_hot_cold_page(page, false);
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+ else
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+ __free_pages_ok(page, order);
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+ }
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+}
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+EXPORT_SYMBOL(__page_frag_drain);
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+
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void *__alloc_page_frag(struct page_frag_cache *nc,
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unsigned int fragsz, gfp_t gfp_mask)
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{
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