Re: [Patch v2 1/2] mm/ksm: get mm_slot by mm_slot_entry() when slot is !NULL

[kernel test robot <lkp@intel.com>]

BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
In-Reply-To: <20250919071244.17020-2-richard.weiyang@gmail.com>
References: <20250919071244.17020-2-richard.weiyang@gmail.com>
TO: Wei Yang <richard.weiyang@gmail.com>

Hi Wei,

kernel test robot noticed the following build warnings:

[auto build test WARNING on akpm-mm/mm-everything]
[also build test WARNING on linus/master v6.17-rc6 next-20250919]
[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/Wei-Yang/mm-ksm-get-mm_slot-by-mm_slot_entry-when-slot-is-NULL/20250919-151547
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20250919071244.17020-2-richard.weiyang%40gmail.com
patch subject: [Patch v2 1/2] mm/ksm: get mm_slot by mm_slot_entry() when slot is !NULL
:::::: branch date: 3 days ago
:::::: commit date: 3 days ago
config: microblaze-randconfig-r073-20250921 (https://download.01.org/0day-ci/archive/20250922/202509220348.96Aa4hMs-lkp@intel.com/config)
compiler: microblaze-linux-gcc (GCC) 12.5.0

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>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202509220348.96Aa4hMs-lkp@intel.com/

New smatch warnings:
mm/ksm.c:2959 __ksm_exit() error: uninitialized symbol 'mm_slot'.

Old smatch warnings:
arch/microblaze/include/asm/thread_info.h:85 current_thread_info() error: uninitialized symbol 'sp'.

vim +/mm_slot +2959 mm/ksm.c

f8af4da3b4c14e Hugh Dickins      2009-09-21  2921  
1c2fb7a4c2ca7a Andrea Arcangeli  2009-09-21  2922  void __ksm_exit(struct mm_struct *mm)
f8af4da3b4c14e Hugh Dickins      2009-09-21  2923  {
21fbd59136e077 Qi Zheng          2022-08-31  2924  	struct ksm_mm_slot *mm_slot;
58730ab6c7cab4 Qi Zheng          2022-08-31  2925  	struct mm_slot *slot;
9ba6929480088a Hugh Dickins      2009-09-21  2926  	int easy_to_free = 0;
cd551f97519d35 Hugh Dickins      2009-09-21  2927  
31dbd01f314364 Izik Eidus        2009-09-21  2928  	/*
9ba6929480088a Hugh Dickins      2009-09-21  2929  	 * This process is exiting: if it's straightforward (as is the
9ba6929480088a Hugh Dickins      2009-09-21  2930  	 * case when ksmd was never running), free mm_slot immediately.
9ba6929480088a Hugh Dickins      2009-09-21  2931  	 * But if it's at the cursor or has rmap_items linked to it, use
c1e8d7c6a7a682 Michel Lespinasse 2020-06-08  2932  	 * mmap_lock to synchronize with any break_cows before pagetables
9ba6929480088a Hugh Dickins      2009-09-21  2933  	 * are freed, and leave the mm_slot on the list for ksmd to free.
9ba6929480088a Hugh Dickins      2009-09-21  2934  	 * Beware: ksm may already have noticed it exiting and freed the slot.
31dbd01f314364 Izik Eidus        2009-09-21  2935  	 */
9ba6929480088a Hugh Dickins      2009-09-21  2936  
cd551f97519d35 Hugh Dickins      2009-09-21  2937  	spin_lock(&ksm_mmlist_lock);
58730ab6c7cab4 Qi Zheng          2022-08-31  2938  	slot = mm_slot_lookup(mm_slots_hash, mm);
de4014f857d062 Wei Yang          2025-09-19  2939  	if (slot) {
58730ab6c7cab4 Qi Zheng          2022-08-31  2940  		mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot);
de4014f857d062 Wei Yang          2025-09-19  2941  		if (ksm_scan.mm_slot != mm_slot) {
6514d511dbe5a7 Hugh Dickins      2009-12-14  2942  			if (!mm_slot->rmap_list) {
58730ab6c7cab4 Qi Zheng          2022-08-31  2943  				hash_del(&slot->hash);
58730ab6c7cab4 Qi Zheng          2022-08-31  2944  				list_del(&slot->mm_node);
9ba6929480088a Hugh Dickins      2009-09-21  2945  				easy_to_free = 1;
9ba6929480088a Hugh Dickins      2009-09-21  2946  			} else {
58730ab6c7cab4 Qi Zheng          2022-08-31  2947  				list_move(&slot->mm_node,
58730ab6c7cab4 Qi Zheng          2022-08-31  2948  					  &ksm_scan.mm_slot->slot.mm_node);
9ba6929480088a Hugh Dickins      2009-09-21  2949  			}
9ba6929480088a Hugh Dickins      2009-09-21  2950  		}
de4014f857d062 Wei Yang          2025-09-19  2951  	}
cd551f97519d35 Hugh Dickins      2009-09-21  2952  	spin_unlock(&ksm_mmlist_lock);
cd551f97519d35 Hugh Dickins      2009-09-21  2953  
9ba6929480088a Hugh Dickins      2009-09-21  2954  	if (easy_to_free) {
58730ab6c7cab4 Qi Zheng          2022-08-31  2955  		mm_slot_free(mm_slot_cache, mm_slot);
12e423ba4eaed7 Lorenzo Stoakes   2025-08-12  2956  		mm_flags_clear(MMF_VM_MERGE_ANY, mm);
12e423ba4eaed7 Lorenzo Stoakes   2025-08-12  2957  		mm_flags_clear(MMF_VM_MERGEABLE, mm);
9ba6929480088a Hugh Dickins      2009-09-21  2958  		mmdrop(mm);
9ba6929480088a Hugh Dickins      2009-09-21 @2959  	} else if (mm_slot) {
d8ed45c5dcd455 Michel Lespinasse 2020-06-08  2960  		mmap_write_lock(mm);
d8ed45c5dcd455 Michel Lespinasse 2020-06-08  2961  		mmap_write_unlock(mm);
9ba6929480088a Hugh Dickins      2009-09-21  2962  	}
739100c88f49a6 Stefan Roesch     2023-02-10  2963  
739100c88f49a6 Stefan Roesch     2023-02-10  2964  	trace_ksm_exit(mm);
31dbd01f314364 Izik Eidus        2009-09-21  2965  }
31dbd01f314364 Izik Eidus        2009-09-21  2966  

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