From: Thomas Gleixner <tglx@linutronix.de>
Date: Sat, 19 Sep 2015 10:15:00 +0200
Subject: mm: rt: Fix generic kmap_atomic for RT
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git
Git-commit: 5d104b01f78caac1fdcbd51ac50e924f4d68d24a
Patch-mainline: Queued in subsystem maintainer repository
References: SLE Realtime Extension

The update to 4.1 brought in the mainline variant of the pagefault
disable distangling from preempt count. That introduced a
preempt_disable/enable pair in the generic kmap_atomic/kunmap_atomic
implementations which got not converted to the _nort() variant.

That results in massive 'scheduling while atomic/sleeping function
called from invalid context' splats.

Fix that up.

Reported-and-tested-by: Juergen Borleis <jbe@pengutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
---
 include/linux/highmem.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -65,7 +65,7 @@ static inline void kunmap(struct page *p
 
 static inline void *kmap_atomic(struct page *page)
 {
-	preempt_disable();
+	preempt_disable_nort();
 	pagefault_disable();
 	return page_address(page);
 }
@@ -74,7 +74,7 @@ static inline void *kmap_atomic(struct p
 static inline void __kunmap_atomic(void *addr)
 {
 	pagefault_enable();
-	preempt_enable();
+	preempt_enable_nort();
 }
 
 #define kmap_atomic_pfn(pfn)	kmap_atomic(pfn_to_page(pfn))