==================================================================
BUG: KCSAN: data-race in __lru_add_drain_all / __pagevec_lru_add

write to 0xffff888237c42528 of 1 bytes by task 3842 on cpu 0:
 pagevec_reinit include/linux/pagevec.h:56 [inline]
 __pagevec_lru_add+0x211/0x240 mm/swap.c:1066
 lru_add_drain_cpu+0x6d/0x270 mm/swap.c:619
 lru_add_drain+0x28/0x40 mm/swap.c:724
 unmap_region+0x5b/0x1d0 mm/mmap.c:2674
 __do_munmap+0xed1/0x1330 mm/mmap.c:2911
 __do_sys_brk+0x267/0x580 mm/mmap.c:257
 __se_sys_brk mm/mmap.c:196 [inline]
 __x64_sys_brk+0x1b/0x20 mm/mmap.c:196
 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 0xffff888237c42528 of 1 bytes by task 4321 on cpu 1:
 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+0x566/0x8f0 drivers/block/loop.c:1402
 loop_clr_fd drivers/block/loop.c:1496 [inline]
 lo_ioctl+0xa48/0x1340 drivers/block/loop.c:1852
 blkdev_ioctl+0x1d0/0x3c0 block/ioctl.c:585
 block_ioctl+0x6d/0x80 fs/block_dev.c:1604
 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_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: 0x0c -> 0x00

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 4321 Comm: syz-executor.4 Not tainted 5.14.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================
loop4: detected capacity change from 0 to 131456
EXT4-fs (loop4): inodes count not valid: 2 vs 32