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BUG: KCSAN: data-race in lru_add_drain_all / lru_cache_add

write to 0xffff88813bd27550 of 1 bytes by task 10439 on cpu 1:
 pagevec_add include/linux/pagevec.h:74 [inline]
 lru_cache_add+0x7c/0x160 mm/swap.c:461
 add_to_page_cache_lru+0x150/0x1b0 mm/filemap.c:956
 pagecache_get_page+0x6a0/0xa30 mm/filemap.c:1808
 grab_cache_page_write_begin+0x3f/0x70 mm/filemap.c:3525
 mext_page_double_lock+0x83/0x280 fs/ext4/move_extent.c:142
 move_extent_per_page+0x38e/0x16c0 fs/ext4/move_extent.c:303
 ext4_move_extents+0xaac/0xc00 fs/ext4/move_extent.c:673
 __ext4_ioctl fs/ext4/ioctl.c:992 [inline]
 ext4_ioctl+0x218f/0x35e0 fs/ext4/ioctl.c:1332
 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+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88813bd27550 of 1 bytes by task 10437 on cpu 0:
 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+0x2c5/0x630 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:1667
 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+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10437 Comm: syz-executor.1 Tainted: G        W         5.12.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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