==================================================================
BUG: KCSAN: data-race in lru_add_drain_all / lru_cache_add

write to 0xffff888237c26468 of 1 bytes by task 23897 on cpu 0:
 pagevec_add include/linux/pagevec.h:74 [inline]
 lru_cache_add+0x74/0x130 mm/swap.c:461
 shmem_getpage_gfp+0xcf8/0x1410 mm/shmem.c:1934
 shmem_getpage mm/shmem.c:155 [inline]
 shmem_write_begin+0x7e/0x100 mm/shmem.c:2530
 generic_perform_write+0x196/0x3a0 mm/filemap.c:3575
 __generic_file_write_iter+0x161/0x300 mm/filemap.c:3704
 generic_file_write_iter+0x75/0x130 mm/filemap.c:3736
 call_write_iter include/linux/fs.h:1977 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x69d/0x770 fs/read_write.c:605
 ksys_pwrite64 fs/read_write.c:712 [inline]
 __do_sys_pwrite64 fs/read_write.c:722 [inline]
 __se_sys_pwrite64 fs/read_write.c:719 [inline]
 __x64_sys_pwrite64+0xf5/0x150 fs/read_write.c:719
 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 23868 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: 23868 Comm: syz-executor.4 Tainted: G        W         5.12.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================
loop4: detected capacity change from 0 to 4101
EXT4-fs (loop4): bad geometry: block count 262272 exceeds size of device (1025 blocks)