DMA reservations: use the new mmap locking API

This use is converted manually ahead of the next patch in the series, as
it requires including a new header which the automated conversion would
miss.

Signed-off-by: Michel Lespinasse <walken@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Reviewed-by: Laurent Dufour <ldufour@linux.ibm.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Liam Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ying Han <yinghan@google.com>
Link: http://lkml.kernel.org/r/20200520052908.204642-4-walken@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/dma-buf/dma-resv.c

@@ -34,6 +34,7 @@
 
 #include <linux/dma-resv.h>
 #include <linux/export.h>
+#include <linux/mm.h>
 #include <linux/sched/mm.h>
 
 /**
@@ -109,7 +110,7 @@ static int __init dma_resv_lockdep(void)
 
 	dma_resv_init(&obj);
 
-	down_read(&mm->mmap_sem);
+	mmap_read_lock(mm);
 	ww_acquire_init(&ctx, &reservation_ww_class);
 	ret = dma_resv_lock(&obj, &ctx);
 	if (ret == -EDEADLK)
@@ -118,7 +119,7 @@ static int __init dma_resv_lockdep(void)
 	fs_reclaim_release(GFP_KERNEL);
 	ww_mutex_unlock(&obj.lock);
 	ww_acquire_fini(&ctx);
-	up_read(&mm->mmap_sem);
+	mmap_read_unlock(mm);
 
 	mmput(mm);