[PATCH 1/7] drm/amdgpu: Avoid reclaim fs while eviction lock

[Christian König]

Am 11.01.20 um 19:39 schrieb Alex Sierra:
> [Why]
> Avoid reclaim filesystem while eviction lock is held called from
> MMU notifier.
>
> [How]
> Setting PF_MEMALLOC_NOFS flags while eviction mutex is locked.
> Using memalloc_nofs_save / memalloc_nofs_restore API.
>
> Change-Id: I5531c9337836e7d4a430df3f16dcc82888e8018c
> Signed-off-by: Alex Sierra <alex.sierra at amd.com>
> Reviewed-by: Felix Kuehling <Felix.Kuehling at amd.com>

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

> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 40 +++++++++++++++++++++-----
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h |  6 +++-
>   2 files changed, 38 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> index b999b67ff57a..d6aba4f9df74 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -82,6 +82,32 @@ struct amdgpu_prt_cb {
>   	struct dma_fence_cb cb;
>   };
>   
> +/**
> + * vm eviction_lock can be taken in MMU notifiers. Make sure no reclaim-FS
> + * happens while holding this lock anywhere to prevent deadlocks when
> + * an MMU notifier runs in reclaim-FS context.
> + */
> +static inline void amdgpu_vm_eviction_lock(struct amdgpu_vm *vm)
> +{
> +	mutex_lock(&vm->eviction_lock);
> +	vm->saved_flags = memalloc_nofs_save();
> +}
> +
> +static inline int amdgpu_vm_eviction_trylock(struct amdgpu_vm *vm)
> +{
> +	if (mutex_trylock(&vm->eviction_lock)) {
> +		vm->saved_flags = memalloc_nofs_save();
> +		return 1;
> +	}
> +	return 0;
> +}
> +
> +static inline void amdgpu_vm_eviction_unlock(struct amdgpu_vm *vm)
> +{
> +	memalloc_nofs_restore(vm->saved_flags);
> +	mutex_unlock(&vm->eviction_lock);
> +}
> +
>   /**
>    * amdgpu_vm_level_shift - return the addr shift for each level
>    *
> @@ -678,9 +704,9 @@ int amdgpu_vm_validate_pt_bos(struct amdgpu_device *adev, struct amdgpu_vm *vm,
>   		}
>   	}
>   
> -	mutex_lock(&vm->eviction_lock);
> +	amdgpu_vm_eviction_lock(vm);
>   	vm->evicting = false;
> -	mutex_unlock(&vm->eviction_lock);
> +	amdgpu_vm_eviction_unlock(vm);
>   
>   	return 0;
>   }
> @@ -1559,7 +1585,7 @@ static int amdgpu_vm_bo_update_mapping(struct amdgpu_device *adev,
>   	if (!(flags & AMDGPU_PTE_VALID))
>   		owner = AMDGPU_FENCE_OWNER_KFD;
>   
> -	mutex_lock(&vm->eviction_lock);
> +	amdgpu_vm_eviction_lock(vm);
>   	if (vm->evicting) {
>   		r = -EBUSY;
>   		goto error_unlock;
> @@ -1576,7 +1602,7 @@ static int amdgpu_vm_bo_update_mapping(struct amdgpu_device *adev,
>   	r = vm->update_funcs->commit(&params, fence);
>   
>   error_unlock:
> -	mutex_unlock(&vm->eviction_lock);
> +	amdgpu_vm_eviction_unlock(vm);
>   	return r;
>   }
>   
> @@ -2537,18 +2563,18 @@ bool amdgpu_vm_evictable(struct amdgpu_bo *bo)
>   		return false;
>   
>   	/* Try to block ongoing updates */
> -	if (!mutex_trylock(&bo_base->vm->eviction_lock))
> +	if (!amdgpu_vm_eviction_trylock(bo_base->vm))
>   		return false;
>   
>   	/* Don't evict VM page tables while they are updated */
>   	if (!dma_fence_is_signaled(bo_base->vm->last_direct) ||
>   	    !dma_fence_is_signaled(bo_base->vm->last_delayed)) {
> -		mutex_unlock(&bo_base->vm->eviction_lock);
> +		amdgpu_vm_eviction_unlock(bo_base->vm);
>   		return false;
>   	}
>   
>   	bo_base->vm->evicting = true;
> -	mutex_unlock(&bo_base->vm->eviction_lock);
> +	amdgpu_vm_eviction_unlock(bo_base->vm);
>   	return true;
>   }
>   
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> index 100547f094ff..c21a36bebc0c 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> @@ -30,6 +30,7 @@
>   #include <drm/gpu_scheduler.h>
>   #include <drm/drm_file.h>
>   #include <drm/ttm/ttm_bo_driver.h>
> +#include <linux/sched/mm.h>
>   
>   #include "amdgpu_sync.h"
>   #include "amdgpu_ring.h"
> @@ -242,9 +243,12 @@ struct amdgpu_vm {
>   	/* tree of virtual addresses mapped */
>   	struct rb_root_cached	va;
>   
> -	/* Lock to prevent eviction while we are updating page tables */
> +	/* Lock to prevent eviction while we are updating page tables
> +	 * use vm_eviction_lock/unlock(vm)
> +	 */
>   	struct mutex		eviction_lock;
>   	bool			evicting;
> +	unsigned int		saved_flags;
>   
>   	/* BOs who needs a validation */
>   	struct list_head	evicted;