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BUG: KCSAN: data-race in isolate_migratepages_block / isolate_migratepages_block

write to 0xffff88812fffc290 of 8 bytes by task 18355 on cpu 0:
 update_cached_migrate mm/compaction.c:418 [inline]
 isolate_migratepages_block+0x1497/0x1710 mm/compaction.c:1065
 isolate_migratepages mm/compaction.c:1831 [inline]
 compact_zone+0x14ea/0x1de0 mm/compaction.c:2183
 compact_zone_order mm/compaction.c:2327 [inline]
 try_to_compact_pages+0x28c/0x5b0 mm/compaction.c:2385
 __alloc_pages_direct_compact+0x89/0x170 mm/page_alloc.c:4000
 __alloc_pages_slowpath+0x29d/0x970 mm/page_alloc.c:4574
 __alloc_pages_nodemask+0x235/0x390 mm/page_alloc.c:4863
 alloc_pages_current+0x21d/0x310 mm/mempolicy.c:2292
 alloc_pages include/linux/gfp.h:545 [inline]
 ion_page_pool_alloc_pages drivers/staging/android/ion/ion_page_pool.c:19 [inline]
 ion_page_pool_alloc+0x230/0x260 drivers/staging/android/ion/ion_page_pool.c:78
 alloc_buffer_page drivers/staging/android/ion/ion_system_heap.c:53 [inline]
 alloc_largest_available drivers/staging/android/ion/ion_system_heap.c:87 [inline]
 ion_system_heap_allocate+0x18a/0x6b0 drivers/staging/android/ion/ion_system_heap.c:118
 ion_buffer_create drivers/staging/android/ion/ion.c:50 [inline]
 ion_alloc drivers/staging/android/ion/ion.c:369 [inline]
 ion_ioctl+0x2d5/0xa00 drivers/staging/android/ion/ion.c:495
 vfs_ioctl fs/ioctl.c:48 [inline]
 ksys_ioctl fs/ioctl.c:753 [inline]
 __do_sys_ioctl fs/ioctl.c:762 [inline]
 __se_sys_ioctl+0xc9/0x130 fs/ioctl.c:760
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:760
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812fffc290 of 8 bytes by task 18361 on cpu 1:
 update_cached_migrate mm/compaction.c:417 [inline]
 isolate_migratepages_block+0x1473/0x1710 mm/compaction.c:1065
 isolate_migratepages mm/compaction.c:1831 [inline]
 compact_zone+0x14ea/0x1de0 mm/compaction.c:2183
 compact_zone_order mm/compaction.c:2327 [inline]
 try_to_compact_pages+0x28c/0x5b0 mm/compaction.c:2385
 __alloc_pages_direct_compact+0x89/0x170 mm/page_alloc.c:4000
 __alloc_pages_slowpath+0x29d/0x970 mm/page_alloc.c:4574
 __alloc_pages_nodemask+0x235/0x390 mm/page_alloc.c:4863
 alloc_pages_current+0x21d/0x310 mm/mempolicy.c:2292
 alloc_pages include/linux/gfp.h:545 [inline]
 ion_page_pool_alloc_pages drivers/staging/android/ion/ion_page_pool.c:19 [inline]
 ion_page_pool_alloc+0x230/0x260 drivers/staging/android/ion/ion_page_pool.c:78
 alloc_buffer_page drivers/staging/android/ion/ion_system_heap.c:53 [inline]
 alloc_largest_available drivers/staging/android/ion/ion_system_heap.c:87 [inline]
 ion_system_heap_allocate+0x18a/0x6b0 drivers/staging/android/ion/ion_system_heap.c:118
 ion_buffer_create drivers/staging/android/ion/ion.c:50 [inline]
 ion_alloc drivers/staging/android/ion/ion.c:369 [inline]
 ion_ioctl+0x2d5/0xa00 drivers/staging/android/ion/ion.c:495
 vfs_ioctl fs/ioctl.c:48 [inline]
 ksys_ioctl fs/ioctl.c:753 [inline]
 __do_sys_ioctl fs/ioctl.c:762 [inline]
 __se_sys_ioctl+0xc9/0x130 fs/ioctl.c:760
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:760
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 18361 Comm: syz-executor.2 Not tainted 5.8.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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