[PATCH 2/3] drm/ttm: remove swap LRU

[Dan Carpenter]

Hi "Christian,

url:    https://github.com/0day-ci/linux/commits/Christian-K-nig/drm-ttm-move-swapout-logic-around/20210210-232812
base:   git://anongit.freedesktop.org/drm/drm-tip drm-tip
config: ia64-randconfig-m031-20210209 (attached as .config)
compiler: ia64-linux-gcc (GCC) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp at intel.com>
Reported-by: Dan Carpenter <dan.carpenter at oracle.com>

New smatch warnings:
drivers/gpu/drm/ttm/ttm_device.c:144 ttm_device_swapout() warn: variable dereferenced before check 'bo->ttm' (see line 142)

vim +144 drivers/gpu/drm/ttm/ttm_device.c

d37e3072dc32c7 Christian König 2021-02-10  125  long ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
d37e3072dc32c7 Christian König 2021-02-10  126  			gfp_t gfp_flags)
d37e3072dc32c7 Christian König 2021-02-10  127  {
d37e3072dc32c7 Christian König 2021-02-10  128  	struct ttm_global *glob = &ttm_glob;
d37e3072dc32c7 Christian König 2021-02-10  129  	struct ttm_resource_manager *man;
22b09b650f7486 Christian König 2021-02-10  130  	struct ttm_buffer_object *bo;
d37e3072dc32c7 Christian König 2021-02-10  131  	unsigned i, j;
22b09b650f7486 Christian König 2021-02-10  132  	int ret;
22b09b650f7486 Christian König 2021-02-10  133  
22b09b650f7486 Christian König 2021-02-10  134  	spin_lock(&glob->lru_lock);
d37e3072dc32c7 Christian König 2021-02-10  135  	for (i = TTM_PL_SYSTEM; i < TTM_NUM_MEM_TYPES; ++i) {
d37e3072dc32c7 Christian König 2021-02-10  136  		man = ttm_manager_type(bdev, i);
d37e3072dc32c7 Christian König 2021-02-10  137  		if (!man || !man->use_tt)
d37e3072dc32c7 Christian König 2021-02-10  138  			continue;
d37e3072dc32c7 Christian König 2021-02-10  139  
d37e3072dc32c7 Christian König 2021-02-10  140  		for (j = 0; j < TTM_MAX_BO_PRIORITY; ++j) {
d37e3072dc32c7 Christian König 2021-02-10  141  			list_for_each_entry(bo, &man->lru[j], lru) {
d37e3072dc32c7 Christian König 2021-02-10 @142  				long num_pages = bo->ttm->num_pages;
                                                                                                 ^^^^^^^^^
Dereferenced

d37e3072dc32c7 Christian König 2021-02-10  143  
d37e3072dc32c7 Christian König 2021-02-10 @144  				if (!bo->ttm ||
                                                                                    ^^^^^^^^
Checked too late

d37e3072dc32c7 Christian König 2021-02-10  145  				    bo->ttm->page_flags & TTM_PAGE_FLAG_SG ||
d37e3072dc32c7 Christian König 2021-02-10  146  				    bo->ttm->page_flags & TTM_PAGE_FLAG_SWAPPED)
d37e3072dc32c7 Christian König 2021-02-10  147  					continue;
22b09b650f7486 Christian König 2021-02-10  148  
22b09b650f7486 Christian König 2021-02-10  149  				ret = ttm_bo_swapout(bo, ctx, gfp_flags);
22b09b650f7486 Christian König 2021-02-10  150  				/* ttm_bo_swapout has dropped the lru_lock */
22b09b650f7486 Christian König 2021-02-10  151  				if (!ret)
22b09b650f7486 Christian König 2021-02-10  152  					return num_pages;
22b09b650f7486 Christian König 2021-02-10  153  				if (ret != -EBUSY)
22b09b650f7486 Christian König 2021-02-10  154  					return ret;
22b09b650f7486 Christian König 2021-02-10  155  			}
22b09b650f7486 Christian König 2021-02-10  156  		}
d37e3072dc32c7 Christian König 2021-02-10  157  	}
22b09b650f7486 Christian König 2021-02-10  158  	spin_unlock(&glob->lru_lock);
22b09b650f7486 Christian König 2021-02-10  159  	return 0;
22b09b650f7486 Christian König 2021-02-10  160  }

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
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