Hi xinhui,

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    
https://github.com/intel-lab-lkp/linux/commits/xinhui-pan/drm-Optimise-for-continuous-memory-allocation/20221218-145922
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    
https://lore.kernel.org/r/20221218065708.93332-1-xinhui.pan%40amd.com
patch subject: [PATCH v6] drm: Optimise for continuous memory allocation
config: s390-randconfig-m041-20221218
compiler: s390-linux-gcc (GCC) 12.1.0

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <l...@intel.com>
| Reported-by: Dan Carpenter <erro...@gmail.com>

smatch warnings:
drivers/gpu/drm/drm_buddy.c:501 find_continuous_blocks() error: uninitialized 
symbol 'block'.

vim +/block +501 drivers/gpu/drm/drm_buddy.c

8a257b57bc11a2 xinhui pan 2022-12-18  472  static struct drm_buddy_block *
8a257b57bc11a2 xinhui pan 2022-12-18  473  find_continuous_blocks(struct 
drm_buddy *mm,
8a257b57bc11a2 xinhui pan 2022-12-18  474                      int order,
8a257b57bc11a2 xinhui pan 2022-12-18  475                      unsigned long 
flags,
8a257b57bc11a2 xinhui pan 2022-12-18  476                      struct 
drm_buddy_block **lb)
8a257b57bc11a2 xinhui pan 2022-12-18  477  {
8a257b57bc11a2 xinhui pan 2022-12-18  478       struct list_head *head = 
&mm->free_list[order - 1];
8a257b57bc11a2 xinhui pan 2022-12-18  479       struct drm_buddy_block 
*free_block, *first = NULL, *last = NULL;
8a257b57bc11a2 xinhui pan 2022-12-18  480  
8a257b57bc11a2 xinhui pan 2022-12-18  481       /*
8a257b57bc11a2 xinhui pan 2022-12-18  482        * Look for continuous free 
memory in buddy and buddy-in-law.
8a257b57bc11a2 xinhui pan 2022-12-18  483        * IOW, the most left blocks at 
right of free block and the most right
8a257b57bc11a2 xinhui pan 2022-12-18  484        * blocks at left of free block.
8a257b57bc11a2 xinhui pan 2022-12-18  485        */
8a257b57bc11a2 xinhui pan 2022-12-18  486  
8a257b57bc11a2 xinhui pan 2022-12-18  487       list_for_each_entry(free_block, 
head, link) {
8a257b57bc11a2 xinhui pan 2022-12-18  488               struct drm_buddy_block 
*buddy, *parent, *block;
8a257b57bc11a2 xinhui pan 2022-12-18  489               int left, min_order = 0;
8a257b57bc11a2 xinhui pan 2022-12-18  490               LIST_HEAD(fbl);
8a257b57bc11a2 xinhui pan 2022-12-18  491  
8a257b57bc11a2 xinhui pan 2022-12-18  492               parent = 
free_block->parent;
8a257b57bc11a2 xinhui pan 2022-12-18  493               if (!parent)
8a257b57bc11a2 xinhui pan 2022-12-18  494                       continue;
8a257b57bc11a2 xinhui pan 2022-12-18  495  
8a257b57bc11a2 xinhui pan 2022-12-18  496               left = parent->left == 
free_block;
8a257b57bc11a2 xinhui pan 2022-12-18  497               
list_add(&free_block->tmp_link, &fbl);
8a257b57bc11a2 xinhui pan 2022-12-18  498               buddy = 
__get_buddy(free_block);
8a257b57bc11a2 xinhui pan 2022-12-18  499               
__continuous_block_in_tree(buddy, &fbl, left, min_order);
8a257b57bc11a2 xinhui pan 2022-12-18  500  
8a257b57bc11a2 xinhui pan 2022-12-18 @501               while (parent && 
!((parent->left == block) ^ left)) {
                                                                                
            ^^^^^
Not initialized on first iteration.

8a257b57bc11a2 xinhui pan 2022-12-18  502                       block = parent;
8a257b57bc11a2 xinhui pan 2022-12-18  503                       parent = 
parent->parent;
8a257b57bc11a2 xinhui pan 2022-12-18  504               }
8a257b57bc11a2 xinhui pan 2022-12-18  505  
8a257b57bc11a2 xinhui pan 2022-12-18  506               if (!parent)
8a257b57bc11a2 xinhui pan 2022-12-18  507                       continue;
8a257b57bc11a2 xinhui pan 2022-12-18  508  
8a257b57bc11a2 xinhui pan 2022-12-18  509               buddy = 
__get_buddy(block);
8a257b57bc11a2 xinhui pan 2022-12-18  510               
__continuous_block_in_tree(buddy, &fbl, !left, min_order);
8a257b57bc11a2 xinhui pan 2022-12-18  511  
8a257b57bc11a2 xinhui pan 2022-12-18  512               /* list head of fbl is 
invalid outside.
8a257b57bc11a2 xinhui pan 2022-12-18  513                * Walk through list 
from first fo last only.
8a257b57bc11a2 xinhui pan 2022-12-18  514                */
8a257b57bc11a2 xinhui pan 2022-12-18  515               if 
(__free_block_in_order(&fbl, free_block, order, &first, &last))
8a257b57bc11a2 xinhui pan 2022-12-18  516                       break;
8a257b57bc11a2 xinhui pan 2022-12-18  517       }
8a257b57bc11a2 xinhui pan 2022-12-18  518  
8a257b57bc11a2 xinhui pan 2022-12-18  519       *lb = last;
8a257b57bc11a2 xinhui pan 2022-12-18  520       return first;
8a257b57bc11a2 xinhui pan 2022-12-18  521  }

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0-DAY CI Kernel Test Service
https://01.org/lkp

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