syzbot

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BUG: KCSAN: data-race in ion_page_pool_free / ion_page_pool_shrink

write to 0xffff888126869484 of 4 bytes by task 821 on cpu 1:
 ion_page_pool_add drivers/staging/android/ion/ion_page_pool.c:36 [inline]
 ion_page_pool_free+0x10a/0x1f0 drivers/staging/android/ion/ion_page_pool.c:87
 free_buffer_page.isra.0+0x10c/0x150 drivers/staging/android/ion/ion_system_heap.c:70
 ion_system_heap_allocate+0x599/0x630 drivers/staging/android/ion/ion_system_heap.c:148
 ion_buffer_create drivers/staging/android/ion/ion.c:50 [inline]
 ion_alloc drivers/staging/android/ion/ion.c:369 [inline]
 ion_ioctl+0x2b9/0xa40 drivers/staging/android/ion/ion.c:495
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x101/0x150 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x47/0x60 fs/ioctl.c:770
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888126869484 of 4 bytes by task 1792 on cpu 0:
 ion_page_pool_total drivers/staging/android/ion/ion_page_pool.c:92 [inline]
 ion_page_pool_shrink+0x230/0x250 drivers/staging/android/ion/ion_page_pool.c:112
 ion_system_heap_shrink+0x64/0xd0 drivers/staging/android/ion/ion_system_heap.c:189
 ion_heap_shrink_count+0x80/0xa0 drivers/staging/android/ion/ion_heap.c:273
 do_shrink_slab+0xb3/0x5b0 mm/vmscan.c:430
 shrink_slab mm/vmscan.c:673 [inline]
 shrink_slab+0x153/0x540 mm/vmscan.c:646
 shrink_node_memcgs mm/vmscan.c:2673 [inline]
 shrink_node+0x354/0x1000 mm/vmscan.c:2777
 kswapd_shrink_node mm/vmscan.c:3523 [inline]
 balance_pgdat+0x641/0xd00 mm/vmscan.c:3681
 kswapd+0x35d/0x800 mm/vmscan.c:3932
 kthread+0x1cb/0x1f0 kernel/kthread.c:255
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1792 Comm: kswapd1 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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