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BUG: KCSAN: data-race in ion_page_pool_shrink / ion_page_pool_shrink

write to 0xffff8882192e4a04 of 4 bytes by task 5874 on cpu 0:
 ion_page_pool_remove drivers/staging/android/ion/ion_page_pool.c:55 [inline]
 ion_page_pool_shrink+0xeb/0x320 drivers/staging/android/ion/ion_page_pool.c:119
 ion_system_heap_shrink+0xab/0x120 drivers/staging/android/ion/ion_system_heap.c:186
 ion_heap_shrink_scan+0xd5/0x100 drivers/staging/android/ion/ion_heap.c:302
 do_shrink_slab+0x286/0x5c0 mm/vmscan.c:518
 shrink_slab+0xea/0x1c0 mm/vmscan.c:679
 shrink_node_memcgs+0x1f9/0x360 mm/vmscan.c:2658
 shrink_node+0x94e/0x1170 mm/vmscan.c:2770
 shrink_zones+0x2af/0x490 mm/vmscan.c:2973
 do_try_to_free_pages+0x1b4/0x6c0 mm/vmscan.c:3026
 try_to_free_pages+0x38d/0x8d0 mm/vmscan.c:3265
 __perform_reclaim mm/page_alloc.c:4223 [inline]
 __alloc_pages_direct_reclaim mm/page_alloc.c:4244 [inline]
 __alloc_pages_slowpath+0x50a/0x970 mm/page_alloc.c:4650
 __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 0xffff8882192e4a04 of 4 bytes by task 5869 on cpu 1:
 ion_page_pool_total drivers/staging/android/ion/ion_page_pool.c:92 [inline]
 ion_page_pool_shrink+0x2b3/0x320 drivers/staging/android/ion/ion_page_pool.c:112
 ion_system_heap_shrink+0xf4/0x120 drivers/staging/android/ion/ion_system_heap.c:186
 ion_heap_shrink_count+0x72/0x90 drivers/staging/android/ion/ion_heap.c:273
 do_shrink_slab+0x86/0x5c0 mm/vmscan.c:436
 shrink_slab+0xea/0x1c0 mm/vmscan.c:679
 shrink_node_memcgs+0x1f9/0x360 mm/vmscan.c:2658
 shrink_node+0x94e/0x1170 mm/vmscan.c:2770
 shrink_zones+0x2af/0x490 mm/vmscan.c:2973
 do_try_to_free_pages+0x1b4/0x6c0 mm/vmscan.c:3026
 try_to_free_pages+0x38d/0x8d0 mm/vmscan.c:3265
 __perform_reclaim mm/page_alloc.c:4223 [inline]
 __alloc_pages_direct_reclaim mm/page_alloc.c:4244 [inline]
 __alloc_pages_slowpath+0x50a/0x970 mm/page_alloc.c:4650
 __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: 5869 Comm: syz-executor.1 Not tainted 5.8.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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