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BUG: KCSAN: data-race in __jbd2_journal_file_buffer / jbd2_journal_dirty_metadata

write to 0xffff88810745c878 of 8 bytes by task 4803 on cpu 1:
 __jbd2_journal_file_buffer+0x18d/0x380 fs/jbd2/transaction.c:2518
 __jbd2_journal_refile_buffer+0x155/0x230 fs/jbd2/transaction.c:2612
 jbd2_journal_commit_transaction+0x24b6/0x3290 fs/jbd2/commit.c:1084
 kjournald2+0x263/0x480 fs/jbd2/journal.c:213
 kthread+0x20b/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff88810745c878 of 8 bytes by task 18257 on cpu 0:
 jbd2_journal_dirty_metadata+0xe3/0x670 fs/jbd2/transaction.c:1477
 __ext4_handle_dirty_metadata+0xc6/0x590 fs/ext4/ext4_jbd2.c:331
 ext4_free_blocks+0x167d/0x1be0 fs/ext4/mballoc.c:5485
 ext4_ext_try_to_merge_up fs/ext4/extents.c:1830 [inline]
 ext4_ext_try_to_merge+0x2fa/0x310 fs/ext4/extents.c:1857
 ext4_swap_extents+0x102d/0x13a0 fs/ext4/extents.c:5693
 move_extent_per_page+0x143c/0x16c0 fs/ext4/move_extent.c:339
 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

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 18257 Comm: syz-executor.5 Not tainted 5.12.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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