Re: [PATCH v7] block: avoid long sync_blockdev() under disk->open_mutex during parallel close

[kernel test robot]

Hi Tetsuo,

kernel test robot noticed the following build warnings:

[auto build test WARNING on axboe/for-next]
[also build test WARNING on linus/master v7.3 next-20261016]
[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/Tetsuo-Handa/block-avoid-long-sync_blockdev-under-disk-open_mutex-during-parallel-close/20261017-004014
base:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git for-next
patch link:    https://lore.kernel.org/r/6efed2d0-fe66-4d29-876b-fd3b74abaa70%40I-love.SAKURA.ne.jp
patch subject: [PATCH v7] block: avoid long sync_blockdev() under disk->open_mutex during parallel close
config: um-x86_64_defconfig (https://download.01.org/0day-ci/archive/20261019/202610191027.uw2yfQhY-lkp@xxxxxxxxx/config)
compiler: clang version 24.0.0git (https://github.com/llvm/llvm-project 6719b9e31d6a93099612c474eec76d9f41d0275a)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20261019/202610191027.uw2yfQhY-lkp@xxxxxxxxx/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@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202610191027.uw2yfQhY-lkp@xxxxxxxxx/

All warnings (new ones prefixed by >>):

>> block/bdev.c:1157:3: warning: releasing mutex 'disk->open_mutex' that was not held [-Wthread-safety-analysis]
    1157 |                 mutex_unlock(&disk->open_mutex);
         |                 ^
>> block/bdev.c:1162:1: warning: mutex 'disk->open_mutex' is not held on every path through here [-Wthread-safety-analysis]
    1162 | }
         | ^
   block/bdev.c:1159:3: note: mutex acquired here
    1159 |                 mutex_lock(&disk->open_mutex);
         |                 ^
   2 warnings generated.


vim +1157 block/bdev.c

  1152	
  1153	static inline void bd_early_sync(struct gendisk *disk, struct block_device *bdev)
  1154	{
  1155		if (atomic_read(&bdev->bd_openers) == 1 + bdev->bd_closers) {
  1156			bdev->bd_closers++;
> 1157			mutex_unlock(&disk->open_mutex);
  1158			sync_blockdev(bdev);
  1159			mutex_lock(&disk->open_mutex);
  1160			bdev->bd_closers--;
  1161		}
> 1162	}
  1163	

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