Re: [PATCH] mm/migrate.c: Rework migration_entry_wait() to not take a pageref

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

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Hi Alistair,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linux/master]
[also build test ERROR on v5.15]
[cannot apply to hnaz-mm/master linus/master next-20211105]
[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/0day-ci/linux/commits/Alistair-Popple/mm-migrate-c-Rework-migration_entry_wait-to-not-take-a-pageref/20211104-183442
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 2f111a6fd5b5297b4e92f53798ca086f7c7d33a4
config: arm-randconfig-r026-20211105 (attached as .config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 847a6807332b13f43704327c2d30103ec0347c77)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install arm cross compiling tool for clang build
        # apt-get install binutils-arm-linux-gnueabi
        # https://github.com/0day-ci/linux/commit/e9447498f8f8758741f3dae044c3e4593130595c
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Alistair-Popple/mm-migrate-c-Rework-migration_entry_wait-to-not-take-a-pageref/20211104-183442
        git checkout e9447498f8f8758741f3dae044c3e4593130595c
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=arm 

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

All errors (new ones prefixed by >>):

>> mm/filemap.c:1468:2: error: implicit declaration of function 'pte_unmap' [-Werror,-Wimplicit-function-declaration]
           pte_unmap_unlock(ptep, ptl);
           ^
   include/linux/mm.h:2275:2: note: expanded from macro 'pte_unmap_unlock'
           pte_unmap(pte);                                 \
           ^
   1 error generated.


vim +/pte_unmap +1468 mm/filemap.c

  1413	
  1414	/**
  1415	 * migration_entry_wait_on_locked - Wait for a migration entry to be removed
  1416	 * @page: page referenced by the migration entry.
  1417	 * @ptep: mapped pte pointer. This function will return with the ptep unmapped.
  1418	 * @ptl: already locked ptl. This function will drop the lock.
  1419	 *
  1420	 * Wait for a migration entry referencing the given page to be removed. This is
  1421	 * equivalent to put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE) except
  1422	 * this can be called without taking a reference on the page. Instead this
  1423	 * should be called while holding the ptl for the migration entry referencing
  1424	 * the page.
  1425	 *
  1426	 * Returns after unmapping and unlocking the pte/ptl with pte_unmap_unlock().
  1427	 *
  1428	 * This follows the same logic as wait_on_page_bit_common() so see the comments
  1429	 * there.
  1430	 */
  1431	void migration_entry_wait_on_locked(struct page *page, pte_t *ptep,
  1432					spinlock_t *ptl)
  1433	{
  1434		struct wait_page_queue wait_page;
  1435		wait_queue_entry_t *wait = &wait_page.wait;
  1436		bool thrashing = false;
  1437		bool delayacct = false;
  1438		unsigned long pflags;
  1439		wait_queue_head_t *q;
  1440	
  1441		q = page_waitqueue(page);
  1442		if (!PageUptodate(page) && PageWorkingset(page)) {
  1443			if (!PageSwapBacked(page)) {
  1444				delayacct_thrashing_start();
  1445				delayacct = true;
  1446			}
  1447			psi_memstall_enter(&pflags);
  1448			thrashing = true;
  1449		}
  1450	
  1451		init_wait(wait);
  1452		wait->func = wake_page_function;
  1453		wait_page.page = page;
  1454		wait_page.bit_nr = PG_locked;
  1455		wait->flags = 0;
  1456	
  1457		spin_lock_irq(&q->lock);
  1458		SetPageWaiters(page);
  1459		if (!trylock_page_bit_common(page, PG_locked, wait))
  1460			__add_wait_queue_entry_tail(q, wait);
  1461		spin_unlock_irq(&q->lock);
  1462	
  1463		/*
  1464		 * If a migration entry exists for the page the migration path must hold
  1465		 * a valid reference to the page, and it must take the ptl to remove the
  1466		 * migration entry. So the page is valid until the ptl is dropped.
  1467		 */
> 1468		pte_unmap_unlock(ptep, ptl);
  1469	
  1470		for (;;) {
  1471			unsigned int flags;
  1472	
  1473			set_current_state(TASK_UNINTERRUPTIBLE);
  1474	
  1475			/* Loop until we've been woken or interrupted */
  1476			flags = smp_load_acquire(&wait->flags);
  1477			if (!(flags & WQ_FLAG_WOKEN)) {
  1478				if (signal_pending_state(TASK_UNINTERRUPTIBLE, current))
  1479					break;
  1480	
  1481				io_schedule();
  1482				continue;
  1483			}
  1484			break;
  1485		}
  1486	
  1487		finish_wait(q, wait);
  1488	
  1489		if (thrashing) {
  1490			if (delayacct)
  1491				delayacct_thrashing_end();
  1492			psi_memstall_leave(&pflags);
  1493		}
  1494	}
  1495	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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