syzbot

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BUG: KCSAN: data-race in balance_pgdat / shrink_node

write to 0xffff88812fffcd18 of 8 bytes by task 1788 on cpu 0:
 balance_pgdat+0xadd/0xd00 mm/vmscan.c:3734
 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

read to 0xffff88812fffcd18 of 8 bytes by task 29307 on cpu 1:
 shrink_node+0xe2b/0x1000 mm/vmscan.c:2761
 shrink_zones mm/vmscan.c:2980 [inline]
 do_try_to_free_pages+0x230/0xb30 mm/vmscan.c:3033
 try_to_free_pages+0x1e6/0x470 mm/vmscan.c:3272
 __perform_reclaim mm/page_alloc.c:4113 [inline]
 __alloc_pages_direct_reclaim mm/page_alloc.c:4134 [inline]
 __alloc_pages_slowpath+0x3cc/0xda0 mm/page_alloc.c:4537
 __alloc_pages_nodemask+0x2c5/0x310 mm/page_alloc.c:4751
 alloc_pages_current+0xca/0x170 mm/mempolicy.c:2211
 alloc_pages include/linux/gfp.h:532 [inline]
 __vmalloc_area_node mm/vmalloc.c:2490 [inline]
 __vmalloc_node_range+0x2de/0x4c0 mm/vmalloc.c:2554
 vmalloc_user+0x63/0x80 mm/vmalloc.c:2684
 vb2_vmalloc_alloc+0xb2/0x1a0 drivers/media/common/videobuf2/videobuf2-vmalloc.c:48
 __vb2_buf_mem_alloc drivers/media/common/videobuf2/videobuf2-core.c:215 [inline]
 __vb2_queue_alloc+0x36d/0x890 drivers/media/common/videobuf2/videobuf2-core.c:370
 vb2_core_create_bufs+0x209/0x5a0 drivers/media/common/videobuf2/videobuf2-core.c:849
 vb2_create_bufs+0x1fb/0x310 drivers/media/common/videobuf2/videobuf2-v4l2.c:750
 vb2_ioctl_create_bufs+0x16b/0x1e0 drivers/media/common/videobuf2/videobuf2-v4l2.c:955
 v4l_create_bufs drivers/media/v4l2-core/v4l2-ioctl.c:2022 [inline]
 v4l_create_bufs+0xa1/0x100 drivers/media/v4l2-core/v4l2-ioctl.c:2009
 __video_do_ioctl+0x3c5/0x6f0 drivers/media/v4l2-core/v4l2-ioctl.c:2925
 video_usercopy+0x1ad/0x8f0 drivers/media/v4l2-core/v4l2-ioctl.c:3237
 video_ioctl2+0x30/0x41 drivers/media/v4l2-core/v4l2-ioctl.c:3274
 v4l2_ioctl+0xe1/0x100 drivers/media/v4l2-core/v4l2-dev.c:360
 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

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 29307 Comm: syz-executor.5 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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