Re: [PATCH] PCI: optimize proc sequential file read

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

BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
In-Reply-To: <20241018054728.116519-1-kanie@linux.alibaba.com>
References: <20241018054728.116519-1-kanie@linux.alibaba.com>
TO: Guixin Liu <kanie@linux.alibaba.com>
TO: bhelgaas@google.com
CC: linux-pci@vger.kernel.org

Hi Guixin,

kernel test robot noticed the following build warnings:

[auto build test WARNING on pci/next]
[also build test WARNING on pci/for-linus linus/master v6.12-rc3 next-20241018]
[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/Guixin-Liu/PCI-optimize-proc-sequential-file-read/20241018-135026
base:   https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git next
patch link:    https://lore.kernel.org/r/20241018054728.116519-1-kanie%40linux.alibaba.com
patch subject: [PATCH] PCI: optimize proc sequential file read
:::::: branch date: 17 hours ago
:::::: commit date: 17 hours ago
config: i386-randconfig-141-20241019 (https://download.01.org/0day-ci/archive/20241019/202410190659.9MCI8EyL-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0

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/202410190659.9MCI8EyL-lkp@intel.com/

smatch warnings:
drivers/pci/proc.c:365 pci_seq_tree_remove_dev() warn: variable dereferenced before check 'dev' (see line 361)

vim +/dev +365 drivers/pci/proc.c

4ca256d9a0e58a Guixin Liu 2024-10-18  358  
4ca256d9a0e58a Guixin Liu 2024-10-18  359  void pci_seq_tree_remove_dev(struct pci_dev *dev)
4ca256d9a0e58a Guixin Liu 2024-10-18  360  {
4ca256d9a0e58a Guixin Liu 2024-10-18 @361  	unsigned long idx = dev->proc_seq_idx;
4ca256d9a0e58a Guixin Liu 2024-10-18  362  	struct pci_dev *latest_dev = NULL;
4ca256d9a0e58a Guixin Liu 2024-10-18  363  	struct pci_dev *ret;
4ca256d9a0e58a Guixin Liu 2024-10-18  364  
4ca256d9a0e58a Guixin Liu 2024-10-18 @365  	if (!dev)
4ca256d9a0e58a Guixin Liu 2024-10-18  366  		return;
4ca256d9a0e58a Guixin Liu 2024-10-18  367  
4ca256d9a0e58a Guixin Liu 2024-10-18  368  	xa_lock(&pci_seq_tree);
4ca256d9a0e58a Guixin Liu 2024-10-18  369  	__xa_erase(&pci_seq_tree, idx);
4ca256d9a0e58a Guixin Liu 2024-10-18  370  	pci_dev_put(dev);
4ca256d9a0e58a Guixin Liu 2024-10-18  371  	/*
4ca256d9a0e58a Guixin Liu 2024-10-18  372  	 * Move the latest pci_dev to this idx to keep the continuity.
4ca256d9a0e58a Guixin Liu 2024-10-18  373  	 */
4ca256d9a0e58a Guixin Liu 2024-10-18  374  	if (idx != pci_max_idx - 1) {
4ca256d9a0e58a Guixin Liu 2024-10-18  375  		latest_dev = __xa_erase(&pci_seq_tree, pci_max_idx - 1);
4ca256d9a0e58a Guixin Liu 2024-10-18  376  		ret = __xa_cmpxchg(&pci_seq_tree, idx, NULL, latest_dev,
4ca256d9a0e58a Guixin Liu 2024-10-18  377  				GFP_KERNEL);
4ca256d9a0e58a Guixin Liu 2024-10-18  378  		if (!ret)
4ca256d9a0e58a Guixin Liu 2024-10-18  379  			latest_dev->proc_seq_idx = idx;
4ca256d9a0e58a Guixin Liu 2024-10-18  380  		WARN_ON(ret);
4ca256d9a0e58a Guixin Liu 2024-10-18  381  	}
4ca256d9a0e58a Guixin Liu 2024-10-18  382  	pci_max_idx--;
4ca256d9a0e58a Guixin Liu 2024-10-18  383  	xa_unlock(&pci_seq_tree);
4ca256d9a0e58a Guixin Liu 2024-10-18  384  }
4ca256d9a0e58a Guixin Liu 2024-10-18  385  

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