From: Thomas Gleixner <tglx@linutronix.de>
Date: Fri, 3 Jul 2009 08:44:34 -0500
Subject: mm/scatterlist: Do not disable irqs on RT
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.6/older/patches-4.6.2-rt5.tar.xz

The local_irq_save() is not only used to get things done "fast" but
also to ensure that in case of SG_MITER_ATOMIC we are in "atomic"
context for kmap_atomic(). For -RT it is enough to keep pagefault
disabled (which is currently handled by kmap_atomic()).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 lib/scatterlist.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -620,7 +620,7 @@ void sg_miter_stop(struct sg_mapping_ite
 			flush_kernel_dcache_page(miter->page);
 
 		if (miter->__flags & SG_MITER_ATOMIC) {
-			WARN_ON_ONCE(preemptible());
+			WARN_ON_ONCE(!pagefault_disabled());
 			kunmap_atomic(miter->addr);
 		} else
 			kunmap(miter->page);
@@ -664,7 +664,7 @@ size_t sg_copy_buffer(struct scatterlist
 	if (!sg_miter_skip(&miter, skip))
 		return false;
 
-	local_irq_save(flags);
+	local_irq_save_nort(flags);
 
 	while (sg_miter_next(&miter) && offset < buflen) {
 		unsigned int len;
@@ -681,7 +681,7 @@ size_t sg_copy_buffer(struct scatterlist
 
 	sg_miter_stop(&miter);
 
-	local_irq_restore(flags);
+	local_irq_restore_nort(flags);
 	return offset;
 }
 EXPORT_SYMBOL(sg_copy_buffer);
