BUG: KCSAN: data-race in __pagevec_lru_add / lru_add_drain_all

write to 0xffff888237c26468 of 1 bytes by task 25773 on cpu 0:
 pagevec_reinit include/linux/pagevec.h:56 [inline]
 __pagevec_lru_add+0x24b/0x280 mm/swap.c:1017
 lru_add_drain_cpu+0x6a/0x260 mm/swap.c:606
 lru_add_drain+0x28/0x40 mm/swap.c:710
 unmap_region+0x5b/0x1d0 mm/mmap.c:2671
 __do_munmap+0xeca/0x1340 mm/mmap.c:2906
 do_munmap mm/mmap.c:2917 [inline]
 munmap_vma_range mm/mmap.c:598 [inline]
 mmap_region+0x58a/0x13e0 mm/mmap.c:1750
 do_mmap+0x77d/0xc90 mm/mmap.c:1581
 vm_mmap_pgoff+0xfc/0x1d0 mm/util.c:519
 ksys_mmap_pgoff+0x2a8/0x380 mm/mmap.c:1632
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888237c26468 of 1 bytes by task 25764 on cpu 1:
 pagevec_count include/linux/pagevec.h:61 [inline]
 lru_add_drain_all+0x108/0x3c0 mm/swap.c:813
 invalidate_bdev+0x50/0x70 fs/block_dev.c:96
 __loop_clr_fd+0x2e2/0x650 drivers/block/loop.c:1241
 loop_clr_fd drivers/block/loop.c:1336 [inline]
 lo_ioctl+0x9eb/0x11f0 drivers/block/loop.c:1694
 blkdev_ioctl+0x1d0/0x3c0 block/ioctl.c:583
 block_ioctl+0x6d/0x80 fs/block_dev.c:1671
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:739
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:739
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 25764 Comm: syz-executor.1 Not tainted 5.12.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================
loop1: detected capacity change from 0 to 1024
EXT4-fs (loop1): bad geometry: first data block 720896 is beyond end of filesystem (54)