linux-kernel - [12/16] export __get_user_pages

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Message-Id: <20111216205043.392878849@clark.kroah.org>
Date:	Fri, 16 Dec 2011 12:49:45 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Greg KH <greg@...ah.com>
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk,
	oprofile-list <oprofile-list@...ts.sourceforge.net>,
	Nick Piggin <npiggin@...e.de>,
	Xiao Guangrong <xiaoguangrong@...fujitsu.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Robert Richter <robert.richter@....com>
Subject: [12/16] export __get_user_pages_fast() function

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------


From: Xiao Guangrong <xiaoguangrong@...fujitsu.com>

commit 45888a0c6edc305495b6bd72a30e66bc40b324c6 upstream.

Backport for stable kernel v2.6.32.y to v2.6.36.y.

Needed for next patch:

 oprofile, x86: Fix nmi-unsafe callgraph support

This function is used by KVM to pin process's page in the atomic context.

Define the 'weak' function to avoid other architecture not support it

Acked-by: Nick Piggin <npiggin@...e.de>
Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
Signed-off-by: Robert Richter <robert.richter@....com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 mm/util.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

--- a/mm/util.c
+++ b/mm/util.c
@@ -233,6 +233,19 @@ void arch_pick_mmap_layout(struct mm_str
 }
 #endif
 
+/*
+ * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
+ * back to the regular GUP.
+ * If the architecture not support this fucntion, simply return with no
+ * page pinned
+ */
+int __attribute__((weak)) __get_user_pages_fast(unsigned long start,
+				 int nr_pages, int write, struct page **pages)
+{
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__get_user_pages_fast);
+
 /**
  * get_user_pages_fast() - pin user pages in memory
  * @start:	starting user address


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