Re: [Linaro-mm-sig] [PATCH] dma-resv: lockdep-prime address_space->i_mmap_rwsem for dma-resv

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Am 28.07.20 um 15:58 schrieb Daniel Vetter:
> 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@intel.com>
> Cc: Sumit Semwal <sumit.semwal@linaro.org>
> Cc: "Christian König" <christian.koenig@amd.com>
> Cc: linux-media@vger.kernel.org
> Cc: linaro-mm-sig@lists.linaro.org
> Cc: Dave Chinner <david@fromorbit.com>
> Cc: Qian Cai <cai@lca.pw>
> Cc: linux-xfs@vger.kernel.org
> Cc: linux-fsdevel@vger.kernel.org
> Cc: Thomas Hellström (Intel) <thomas_os@shipmail.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Jason Gunthorpe <jgg@mellanox.com>
> Cc: linux-mm@kvack.org
> Cc: linux-rdma@vger.kernel.org
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

Reviewed-by: Christian König <christian.koenig@amd.com>

> ---
>   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();