* Re: [PATCH] mm/migrate.c: Rework migration_entry_wait() to not take a pageref
2021-11-05 9:50 ` [PATCH] mm/migrate.c: Rework migration_entry_wait() to not take a pageref kernel test robot
@ 2021-11-08 7:21 ` Alistair Popple
0 siblings, 0 replies; 2+ messages in thread
From: Alistair Popple @ 2021-11-08 7:21 UTC (permalink / raw)
To: akpm@linux-foundation.org, kernel test robot
Cc: llvm@lists.linux.dev, kbuild-all@lists.01.org,
willy@infradead.org, dhowells@redhat.com, hughd@google.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
jglisse@redhat.com, Jason Gunthorpe, Ralph Campbell, John Hubbard
Got this after sending v2 but it will have the same problem. This occurs for
CONFIG_MMU=n which seems to be broken anyway due to other arch build errors (at
least for Arm SA1100 based builds). Fixing this is easy enough though - only
defining migration_entry_wait_on_locked() when CONFIG_MIGRATION=y fixes this
and is probably a good idea anyway.
I will wait a bit for feedback on v2 before sending v3 with this fix.
- Alistair
On Friday, 5 November 2021 8:50:08 PM AEDT kernel test robot wrote:
> 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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