.fault now can retry.  The retry can break state machine of .fault.  In
filemap_fault, if page is miss, ra->mmap_miss is increased.  In the second
try, since the page is in page cache now, ra->mmap_miss is decreased.  And
these are done in one fault, so we can't detect random mmap file access.

Add a new flag to indicate .fault is tried once.  In the second try, skip
ra->mmap_miss decreasing.  The filemap_fault state machine is ok with it.

I only tested x86, didn't test other archs, but looks the change for other
archs is obvious, but who knows :)
Signed-off-by: NShaohua Li <shaohua.li@fusionio.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Commit d065bd81
(mm: retry page fault when blocking on disk transfer) and
commit 37b23e05
(x86,mm: make pagefault killable)

The above commits introduced changes into the x86 pagefault handler
for making the page fault handler retryable as well as killable.

These changes reduce the mmap_sem hold time, which is crucial
during OOM killer invocation.

Port these changes to openrisc.
Signed-off-by: NMohd. Faris <mohdfarisq2010@gmail.com>
Signed-off-by: NKautuk Consul <consul.kautuk@gmail.com>
Signed-off-by: NJonas Bonn <jonas@southpole.se>

Disintegrate asm/system.h for OpenRISC.  Not compiled.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>
cc: linux@lists.openrisc.net

Use BUG_ON(x) rather than if(x) BUG();

The semantic patch that fixes this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@ identifier x; @@
-if (x) BUG();
+BUG_ON(x);

@@ identifier x; @@
-if (!x) BUG();
+BUG_ON(!x);
// </smpl>
Signed-off-by: NJulia Lawall <julia@diku.dk>
Signed-off-by: NJonas Bonn <jonas@southpole.se>

Signed-off-by: NJonas Bonn <jonas@southpole.se>
Reviewed-by: NArnd Bergmann <arnd@arndb.de>

Signed-off-by: NJonas Bonn <jonas@southpole.se>
Reviewed-by: NArnd Bergmann <arnd@arndb.de>