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BUG: KCSAN: data-race in delete_from_page_cache_batch / migrate_pages

write to 0xffffea0004ebf9d8 of 8 bytes by task 29683 on cpu 0:
 page_cache_delete_batch mm/filemap.c:318 [inline]
 delete_from_page_cache_batch+0x2fc/0x690 mm/filemap.c:349
 truncate_inode_pages_range+0x1a5/0xa70 mm/truncate.c:326
 truncate_inode_pages mm/truncate.c:424 [inline]
 truncate_pagecache+0x4f/0x70 mm/truncate.c:736
 ext4_setattr+0xa21/0xec0 fs/ext4/inode.c:5498
 notify_change+0x8a3/0xa80 fs/attr.c:398
 do_truncate+0xe8/0x130 fs/open.c:64
 handle_truncate fs/namei.c:3030 [inline]
 do_open fs/namei.c:3378 [inline]
 path_openat+0x19b2/0x1f20 fs/namei.c:3507
 do_filp_open+0xe9/0x200 fs/namei.c:3534
 do_sys_openat2+0xa3/0x250 fs/open.c:1204
 do_sys_open fs/open.c:1220 [inline]
 __do_sys_openat fs/open.c:1236 [inline]
 __se_sys_openat fs/open.c:1231 [inline]
 __x64_sys_openat+0xef/0x110 fs/open.c:1231
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffffea0004ebf9d8 of 8 bytes by task 29731 on cpu 1:
 __PageMovable include/linux/page-flags.h:498 [inline]
 __unmap_and_move mm/migrate.c:964 [inline]
 unmap_and_move mm/migrate.c:1136 [inline]
 migrate_pages+0x3cb/0x1530 mm/migrate.c:1411
 do_mbind+0xd43/0xf50 mm/mempolicy.c:1340
 kernel_mbind mm/mempolicy.c:1475 [inline]
 __do_sys_mbind mm/mempolicy.c:1482 [inline]
 __se_sys_mbind mm/mempolicy.c:1478 [inline]
 __x64_sys_mbind+0x10a/0x130 mm/mempolicy.c:1478
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0xffff888106b3b798 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 29731 Comm: syz-executor.0 Not tainted 5.14.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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