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BUG: KCSAN: data-race in ion_page_pool_remove / ion_page_pool_shrink

write to 0xffff888126f6ca04 of 4 bytes by task 19026 on cpu 0:
 ion_page_pool_remove+0xd7/0x210 drivers/staging/android/ion/ion_page_pool.c:55
 ion_page_pool_alloc+0x12d/0x180 drivers/staging/android/ion/ion_page_pool.c:74
 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+0x1cc/0x620 drivers/staging/android/ion/ion_system_heap.c:118
 ion_buffer_create drivers/staging/android/ion/ion.c:57 [inline]
 ion_alloc drivers/staging/android/ion/ion.c:383 [inline]
 ion_ioctl+0x8f0/0xab0 drivers/staging/android/ion/ion.c:509
 vfs_ioctl fs/ioctl.c:47 [inline]
 file_ioctl fs/ioctl.c:545 [inline]
 do_vfs_ioctl+0x84f/0xcf0 fs/ioctl.c:732
 ksys_ioctl+0xbd/0xe0 fs/ioctl.c:749
 __do_sys_ioctl fs/ioctl.c:756 [inline]
 __se_sys_ioctl fs/ioctl.c:754 [inline]
 __x64_sys_ioctl+0x4c/0x60 fs/ioctl.c:754
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888126f6ca04 of 4 bytes by task 1768 on cpu 1:
 ion_page_pool_total drivers/staging/android/ion/ion_page_pool.c:92 [inline]
 ion_page_pool_shrink+0x238/0x250 drivers/staging/android/ion/ion_page_pool.c:112
 ion_system_heap_shrink+0x69/0xe0 drivers/staging/android/ion/ion_system_heap.c:189
 ion_heap_shrink_count+0x83/0xa0 drivers/staging/android/ion/ion_heap.c:273
 do_shrink_slab+0xb7/0x5a0 mm/vmscan.c:444
 shrink_slab mm/vmscan.c:687 [inline]
 shrink_slab+0x147/0x540 mm/vmscan.c:660
 shrink_node_memcgs mm/vmscan.c:2687 [inline]
 shrink_node+0x34a/0xfe0 mm/vmscan.c:2791
 kswapd_shrink_node mm/vmscan.c:3539 [inline]
 balance_pgdat+0x68d/0xda0 mm/vmscan.c:3697
 kswapd+0x35b/0x800 mm/vmscan.c:3948
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1768 Comm: kswapd0 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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