[PATCH] drm/ttm: Fix ttm_bo_shrink() infinite LRU walk on backup failure

[PATCH] drm/ttm: Fix ttm_bo_shrink() infinite LRU walk on backup failure

[Thomas Hellström]

Apply the same fix as b2ed01e7ad ("drm/ttm: Fix ttm_bo_swapout()
infinite LRU walk on swapout failure") to the ttm_bo_shrink() path.

Move del_bulk_move from before the backup to after success only,
using ttm_resource_del_bulk_move_unevictable() since the resource
is now unevictable once fully backed up.

Fixes: 70d645deac98 ("drm/ttm: Add helpers for shrinking")
Cc: Christian König <christian.koenig@amd.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v6.15+
Assisted-by: GitHub_Copilot:claude-opus-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/ttm/ttm_bo_util.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
index f83b7d5ec6c6..3e3c201a0222 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -1112,19 +1112,14 @@ long ttm_bo_shrink(struct ttm_operation_ctx *ctx, struct ttm_buffer_object *bo,
 	if (lret < 0)
 		return lret;
 
-	if (bo->bulk_move) {
-		spin_lock(&bdev->lru_lock);
-		ttm_resource_del_bulk_move(bo->resource, bo);
-		spin_unlock(&bdev->lru_lock);
-	}
-
 	lret = ttm_tt_backup(bdev, bo->ttm, (struct ttm_backup_flags)
 			     {.purge = flags.purge,
 			      .writeback = flags.writeback});
 
-	if (lret <= 0 && bo->bulk_move) {
+	if (lret > 0) {
 		spin_lock(&bdev->lru_lock);
-		ttm_resource_add_bulk_move(bo->resource, bo);
+		ttm_resource_del_bulk_move_unevictable(bo->resource, bo);
+		ttm_resource_move_to_lru_tail(bo->resource);
 		spin_unlock(&bdev->lru_lock);
 	}
 
-- 
2.54.0

Re: [PATCH] drm/ttm: Fix ttm_bo_shrink() infinite LRU walk on backup failure

[Matthew Auld]

On 11/05/2026 17:24, Thomas Hellström wrote:
> Apply the same fix as b2ed01e7ad ("drm/ttm: Fix ttm_bo_swapout()
> infinite LRU walk on swapout failure") to the ttm_bo_shrink() path.
> 
> Move del_bulk_move from before the backup to after success only,
> using ttm_resource_del_bulk_move_unevictable() since the resource
> is now unevictable once fully backed up.
> 
> Fixes: 70d645deac98 ("drm/ttm: Add helpers for shrinking")
> Cc: Christian König <christian.koenig@amd.com>
> Cc: Huang Rui <ray.huang@amd.com>
> Cc: Matthew Auld <matthew.auld@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Dave Airlie <airlied@redhat.com>
> Cc: dri-devel@lists.freedesktop.org
> Cc: <stable@vger.kernel.org> # v6.15+
> Assisted-by: GitHub_Copilot:claude-opus-4.6
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>

Reviewed-by: Matthew Auld <matthew.auld@intel.com>

> ---
>   drivers/gpu/drm/ttm/ttm_bo_util.c | 11 +++--------
>   1 file changed, 3 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
> index f83b7d5ec6c6..3e3c201a0222 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_util.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
> @@ -1112,19 +1112,14 @@ long ttm_bo_shrink(struct ttm_operation_ctx *ctx, struct ttm_buffer_object *bo,
>   	if (lret < 0)
>   		return lret;
>   
> -	if (bo->bulk_move) {
> -		spin_lock(&bdev->lru_lock);
> -		ttm_resource_del_bulk_move(bo->resource, bo);
> -		spin_unlock(&bdev->lru_lock);
> -	}
> -
>   	lret = ttm_tt_backup(bdev, bo->ttm, (struct ttm_backup_flags)
>   			     {.purge = flags.purge,
>   			      .writeback = flags.writeback});
>   
> -	if (lret <= 0 && bo->bulk_move) {
> +	if (lret > 0) {
>   		spin_lock(&bdev->lru_lock);
> -		ttm_resource_add_bulk_move(bo->resource, bo);
> +		ttm_resource_del_bulk_move_unevictable(bo->resource, bo);
> +		ttm_resource_move_to_lru_tail(bo->resource);
>   		spin_unlock(&bdev->lru_lock);
>   	}
>   

Re: [PATCH] drm/ttm: Fix ttm_bo_shrink() infinite LRU walk on backup failure

[kernel test robot]

Hi Thomas,

kernel test robot noticed the following build errors:

[auto build test ERROR on drm-misc/drm-misc-next]
[also build test ERROR on linus/master v7.1-rc3 next-20260508]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Thomas-Hellstr-m/drm-ttm-Fix-ttm_bo_shrink-infinite-LRU-walk-on-backup-failure/20260513-095356
base:   https://gitlab.freedesktop.org/drm/misc/kernel.git drm-misc-next
patch link:    https://lore.kernel.org/r/20260511162443.24352-1-thomas.hellstrom%40linux.intel.com
patch subject: [PATCH] drm/ttm: Fix ttm_bo_shrink() infinite LRU walk on backup failure
config: powerpc-allmodconfig (https://download.01.org/0day-ci/archive/20260513/202605131522.yUSpVs9Q-lkp@intel.com/config)
compiler: powerpc64-linux-gcc (GCC) 15.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260513/202605131522.yUSpVs9Q-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202605131522.yUSpVs9Q-lkp@intel.com/

All errors (new ones prefixed by >>):

   drivers/gpu/drm/ttm/ttm_bo_util.c: In function 'ttm_bo_shrink':
>> drivers/gpu/drm/ttm/ttm_bo_util.c:1121:17: error: implicit declaration of function 'ttm_resource_del_bulk_move_unevictable'; did you mean 'ttm_resource_del_bulk_move'? [-Wimplicit-function-declaration]
    1121 |                 ttm_resource_del_bulk_move_unevictable(bo->resource, bo);
         |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
         |                 ttm_resource_del_bulk_move


vim +1121 drivers/gpu/drm/ttm/ttm_bo_util.c

  1067	
  1068	/**
  1069	 * ttm_bo_shrink() - Helper to shrink a ttm buffer object.
  1070	 * @ctx: The struct ttm_operation_ctx used for the shrinking operation.
  1071	 * @bo: The buffer object.
  1072	 * @flags: Flags governing the shrinking behaviour.
  1073	 *
  1074	 * The function uses the ttm_tt_back_up functionality to back up or
  1075	 * purge a struct ttm_tt. If the bo is not in system, it's first
  1076	 * moved there.
  1077	 *
  1078	 * Return: The number of pages shrunken or purged, or
  1079	 * negative error code on failure.
  1080	 */
  1081	long ttm_bo_shrink(struct ttm_operation_ctx *ctx, struct ttm_buffer_object *bo,
  1082			   const struct ttm_bo_shrink_flags flags)
  1083	{
  1084		static const struct ttm_place sys_placement_flags = {
  1085			.fpfn = 0,
  1086			.lpfn = 0,
  1087			.mem_type = TTM_PL_SYSTEM,
  1088			.flags = 0,
  1089		};
  1090		static struct ttm_placement sys_placement = {
  1091			.num_placement = 1,
  1092			.placement = &sys_placement_flags,
  1093		};
  1094		struct ttm_device *bdev = bo->bdev;
  1095		long lret;
  1096	
  1097		dma_resv_assert_held(bo->base.resv);
  1098	
  1099		if (flags.allow_move && bo->resource->mem_type != TTM_PL_SYSTEM) {
  1100			int ret = ttm_bo_validate(bo, &sys_placement, ctx);
  1101	
  1102			/* Consider -ENOMEM and -ENOSPC non-fatal. */
  1103			if (ret) {
  1104				if (ret == -ENOMEM || ret == -ENOSPC)
  1105					ret = -EBUSY;
  1106				return ret;
  1107			}
  1108		}
  1109	
  1110		ttm_bo_unmap_virtual(bo);
  1111		lret = ttm_bo_wait_ctx(bo, ctx);
  1112		if (lret < 0)
  1113			return lret;
  1114	
  1115		lret = ttm_tt_backup(bdev, bo->ttm, (struct ttm_backup_flags)
  1116				     {.purge = flags.purge,
  1117				      .writeback = flags.writeback});
  1118	
  1119		if (lret > 0) {
  1120			spin_lock(&bdev->lru_lock);
> 1121			ttm_resource_del_bulk_move_unevictable(bo->resource, bo);
  1122			ttm_resource_move_to_lru_tail(bo->resource);
  1123			spin_unlock(&bdev->lru_lock);
  1124		}
  1125	
  1126		if (lret < 0 && lret != -EINTR)
  1127			return -EBUSY;
  1128	
  1129		return lret;
  1130	}
  1131	EXPORT_SYMBOL(ttm_bo_shrink);
  1132	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH] drm/ttm: Fix ttm_bo_shrink() infinite LRU walk on backup failure

[kernel test robot]

Hi Thomas,

kernel test robot noticed the following build errors:

[auto build test ERROR on drm-misc/drm-misc-next]
[also build test ERROR on linus/master v7.1-rc3 next-20260508]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Thomas-Hellstr-m/drm-ttm-Fix-ttm_bo_shrink-infinite-LRU-walk-on-backup-failure/20260513-095356
base:   https://gitlab.freedesktop.org/drm/misc/kernel.git drm-misc-next
patch link:    https://lore.kernel.org/r/20260511162443.24352-1-thomas.hellstrom%40linux.intel.com
patch subject: [PATCH] drm/ttm: Fix ttm_bo_shrink() infinite LRU walk on backup failure
config: x86_64-allmodconfig (https://download.01.org/0day-ci/archive/20260513/202605131824.SbQ7agaE-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260513/202605131824.SbQ7agaE-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202605131824.SbQ7agaE-lkp@intel.com/

All errors (new ones prefixed by >>):

>> drivers/gpu/drm/ttm/ttm_bo_util.c:1121:3: error: call to undeclared function 'ttm_resource_del_bulk_move_unevictable'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
    1121 |                 ttm_resource_del_bulk_move_unevictable(bo->resource, bo);
         |                 ^
   drivers/gpu/drm/ttm/ttm_bo_util.c:1121:3: note: did you mean 'ttm_resource_del_bulk_move'?
   include/drm/ttm/ttm_resource.h:449:6: note: 'ttm_resource_del_bulk_move' declared here
     449 | void ttm_resource_del_bulk_move(struct ttm_resource *res,
         |      ^
   1 error generated.


vim +/ttm_resource_del_bulk_move_unevictable +1121 drivers/gpu/drm/ttm/ttm_bo_util.c

  1067	
  1068	/**
  1069	 * ttm_bo_shrink() - Helper to shrink a ttm buffer object.
  1070	 * @ctx: The struct ttm_operation_ctx used for the shrinking operation.
  1071	 * @bo: The buffer object.
  1072	 * @flags: Flags governing the shrinking behaviour.
  1073	 *
  1074	 * The function uses the ttm_tt_back_up functionality to back up or
  1075	 * purge a struct ttm_tt. If the bo is not in system, it's first
  1076	 * moved there.
  1077	 *
  1078	 * Return: The number of pages shrunken or purged, or
  1079	 * negative error code on failure.
  1080	 */
  1081	long ttm_bo_shrink(struct ttm_operation_ctx *ctx, struct ttm_buffer_object *bo,
  1082			   const struct ttm_bo_shrink_flags flags)
  1083	{
  1084		static const struct ttm_place sys_placement_flags = {
  1085			.fpfn = 0,
  1086			.lpfn = 0,
  1087			.mem_type = TTM_PL_SYSTEM,
  1088			.flags = 0,
  1089		};
  1090		static struct ttm_placement sys_placement = {
  1091			.num_placement = 1,
  1092			.placement = &sys_placement_flags,
  1093		};
  1094		struct ttm_device *bdev = bo->bdev;
  1095		long lret;
  1096	
  1097		dma_resv_assert_held(bo->base.resv);
  1098	
  1099		if (flags.allow_move && bo->resource->mem_type != TTM_PL_SYSTEM) {
  1100			int ret = ttm_bo_validate(bo, &sys_placement, ctx);
  1101	
  1102			/* Consider -ENOMEM and -ENOSPC non-fatal. */
  1103			if (ret) {
  1104				if (ret == -ENOMEM || ret == -ENOSPC)
  1105					ret = -EBUSY;
  1106				return ret;
  1107			}
  1108		}
  1109	
  1110		ttm_bo_unmap_virtual(bo);
  1111		lret = ttm_bo_wait_ctx(bo, ctx);
  1112		if (lret < 0)
  1113			return lret;
  1114	
  1115		lret = ttm_tt_backup(bdev, bo->ttm, (struct ttm_backup_flags)
  1116				     {.purge = flags.purge,
  1117				      .writeback = flags.writeback});
  1118	
  1119		if (lret > 0) {
  1120			spin_lock(&bdev->lru_lock);
> 1121			ttm_resource_del_bulk_move_unevictable(bo->resource, bo);
  1122			ttm_resource_move_to_lru_tail(bo->resource);
  1123			spin_unlock(&bdev->lru_lock);
  1124		}
  1125	
  1126		if (lret < 0 && lret != -EINTR)
  1127			return -EBUSY;
  1128	
  1129		return lret;
  1130	}
  1131	EXPORT_SYMBOL(ttm_bo_shrink);
  1132	

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki