Re: [PATCH v12 2/7] mm: factor helpers for memory_failure_dev_pagemap

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

Hi Shiyang,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on hnaz-mm/master]
[also build test WARNING on next-20220408]
[cannot apply to xfs-linux/for-next linus/master linux/master v5.18-rc1]
[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]

url:    https://github.com/intel-lab-lkp/linux/commits/Shiyang-Ruan/fsdax-introduce-fs-query-to-support-reflink/20220411-001048
base:   https://github.com/hnaz/linux-mm master
config: x86_64-randconfig-a011 (https://download.01.org/0day-ci/archive/20220411/202204110420.O844CZYb-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.2.0-19) 11.2.0
reproduce (this is a W=1 build):
        # https://github.com/intel-lab-lkp/linux/commit/9ab00d3f6d4d9d3d2e4446480567af17c8726bd2
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Shiyang-Ruan/fsdax-introduce-fs-query-to-support-reflink/20220411-001048
        git checkout 9ab00d3f6d4d9d3d2e4446480567af17c8726bd2
        # save the config file to linux build tree
        mkdir build_dir
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   mm/memory-failure.c: In function 'mf_generic_kill_procs':
>> mm/memory-failure.c:1533:13: warning: variable 'rc' set but not used [-Wunused-but-set-variable]
    1533 |         int rc = 0;
         |             ^~


vim +/rc +1533 mm/memory-failure.c

  1526	
  1527	static int mf_generic_kill_procs(unsigned long long pfn, int flags,
  1528			struct dev_pagemap *pgmap)
  1529	{
  1530		struct page *page = pfn_to_page(pfn);
  1531		LIST_HEAD(to_kill);
  1532		dax_entry_t cookie;
> 1533		int rc = 0;
  1534	
  1535		/*
  1536		 * Pages instantiated by device-dax (not filesystem-dax)
  1537		 * may be compound pages.
  1538		 */
  1539		page = compound_head(page);
  1540	
  1541		/*
  1542		 * Prevent the inode from being freed while we are interrogating
  1543		 * the address_space, typically this would be handled by
  1544		 * lock_page(), but dax pages do not use the page lock. This
  1545		 * also prevents changes to the mapping of this pfn until
  1546		 * poison signaling is complete.
  1547		 */
  1548		cookie = dax_lock_page(page);
  1549		if (!cookie)
  1550			return -EBUSY;
  1551	
  1552		if (hwpoison_filter(page)) {
  1553			rc = -EOPNOTSUPP;
  1554			goto unlock;
  1555		}
  1556	
  1557		if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
  1558			/*
  1559			 * TODO: Handle HMM pages which may need coordination
  1560			 * with device-side memory.
  1561			 */
  1562			return -EBUSY;
  1563		}
  1564	
  1565		/*
  1566		 * Use this flag as an indication that the dax page has been
  1567		 * remapped UC to prevent speculative consumption of poison.
  1568		 */
  1569		SetPageHWPoison(page);
  1570	
  1571		/*
  1572		 * Unlike System-RAM there is no possibility to swap in a
  1573		 * different physical page at a given virtual address, so all
  1574		 * userspace consumption of ZONE_DEVICE memory necessitates
  1575		 * SIGBUS (i.e. MF_MUST_KILL)
  1576		 */
  1577		flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
  1578		collect_procs(page, &to_kill, true);
  1579	
  1580		unmap_and_kill(&to_kill, pfn, page->mapping, page->index, flags);
  1581	unlock:
  1582		dax_unlock_page(page, cookie);
  1583		return 0;
  1584	}
  1585	

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