[PATCH] dma-resv: lockdep-prime address_space->i_mmap_rwsem for dma-resv

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GPU drivers need this in their shrinkers, to be able to throw out
mmap'ed buffers. Note that we also need dma_resv_lock in shrinkers,
but that loop is resolved by trylocking in shrinkers.

So full hierarchy is now (ignore some of the other branches we already
have primed):

mmap_read_lock -> dma_resv -> shrinkers -> i_mmap_lock_write

I hope that's not inconsistent with anything mm or fs does, adding
relevant people.

Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
Cc: "Christian König" <christian.koenig@xxxxxxx>
Cc: linux-media@xxxxxxxxxxxxxxx
Cc: linaro-mm-sig@xxxxxxxxxxxxxxxx
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Qian Cai <cai@xxxxxx>
Cc: linux-xfs@xxxxxxxxxxxxxxx
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: Thomas Hellström (Intel) <thomas_os@xxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-rdma@xxxxxxxxxxxxxxx
Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
---
 drivers/dma-buf/dma-resv.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index 0e6675ec1d11..9678162a4ac5 100644
--- a/drivers/dma-buf/dma-resv.c
+++ b/drivers/dma-buf/dma-resv.c
@@ -104,12 +104,14 @@ static int __init dma_resv_lockdep(void)
 	struct mm_struct *mm = mm_alloc();
 	struct ww_acquire_ctx ctx;
 	struct dma_resv obj;
+	struct address_space mapping;
 	int ret;
 
 	if (!mm)
 		return -ENOMEM;
 
 	dma_resv_init(&obj);
+	address_space_init_once(&mapping);
 
 	mmap_read_lock(mm);
 	ww_acquire_init(&ctx, &reservation_ww_class);
@@ -117,6 +119,9 @@ static int __init dma_resv_lockdep(void)
 	if (ret == -EDEADLK)
 		dma_resv_lock_slow(&obj, &ctx);
 	fs_reclaim_acquire(GFP_KERNEL);
+	/* for unmap_mapping_range on trylocked buffer objects in shrinkers */
+	i_mmap_lock_write(&mapping);
+	i_mmap_unlock_write(&mapping);
 #ifdef CONFIG_MMU_NOTIFIER
 	lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
 	__dma_fence_might_wait();
-- 
2.27.0

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