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BUG: KCSAN: data-race in __lru_add_drain_all / __pagevec_lru_add

write to 0xffff888237d264a8 of 1 bytes by task 23897 on cpu 1:
 pagevec_reinit include/linux/pagevec.h:56 [inline]
 __pagevec_lru_add+0x27a/0x2b0 mm/swap.c:1066
 lru_add_drain_cpu+0x6d/0x270 mm/swap.c:619
 lru_add_drain+0x28/0x40 mm/swap.c:724
 exit_mmap+0x199/0x400 mm/mmap.c:3203
 __mmput+0x27/0x1c0 kernel/fork.c:1096
 mmput+0x3d/0x50 kernel/fork.c:1117
 free_bprm+0xce/0x1f0 fs/exec.c:1478
 kernel_execve+0x4e9/0x640 fs/exec.c:1975
 call_usermodehelper_exec_async+0x1d8/0x290 kernel/umh.c:112
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff888237d264a8 of 1 bytes by task 23867 on cpu 0:
 pagevec_count include/linux/pagevec.h:61 [inline]
 __lru_add_drain_all+0x12c/0x3e0 mm/swap.c:828
 lru_add_drain_all+0xc/0x10 mm/swap.c:850
 invalidate_bdev+0x50/0x70 fs/block_dev.c:96
 __loop_clr_fd+0x2e2/0x640 drivers/block/loop.c:1242
 loop_clr_fd drivers/block/loop.c:1337 [inline]
 lo_ioctl+0x9eb/0x11f0 drivers/block/loop.c:1695
 blkdev_ioctl+0x1d0/0x3c0 block/ioctl.c:585
 block_ioctl+0x6d/0x80 fs/block_dev.c:1664
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:1069 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:1055
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:1055
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 23867 Comm: syz-executor.1 Not tainted 5.13.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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loop1: detected capacity change from 0 to 264192
EXT4-fs (loop1): Invalid log block size: 1024