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BUG: KCSAN: data-race in __jbd2_journal_drop_transaction / start_this_handle

write to 0xffff888102bdd878 of 8 bytes by task 20648 on cpu 0:
 jbd2_get_transaction fs/jbd2/transaction.c:125 [inline]
 start_this_handle+0xf1b/0x1250 fs/jbd2/transaction.c:416
 jbd2__journal_start+0x1fc/0x3b0 fs/jbd2/transaction.c:525
 __ext4_journal_start_sb+0x159/0x2d0 fs/ext4/ext4_jbd2.c:105
 __ext4_new_inode+0xd9c/0x2fd0 fs/ext4/ialloc.c:1080
 ext4_symlink+0x2cc/0x700 fs/ext4/namei.c:3293
 vfs_symlink+0x23f/0x350 fs/namei.c:4250
 do_symlinkat+0x104/0x380 fs/namei.c:4279
 __do_sys_symlink fs/namei.c:4301 [inline]
 __se_sys_symlink fs/namei.c:4299 [inline]
 __x64_sys_symlink+0x52/0x60 fs/namei.c:4299
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888102bdd878 of 8 bytes by task 345 on cpu 1:
 __jbd2_journal_drop_transaction+0x1f0/0x2c0 fs/jbd2/checkpoint.c:803
 __jbd2_journal_remove_checkpoint+0x2d5/0x370 fs/jbd2/checkpoint.c:734
 jbd2_journal_commit_transaction+0x246e/0x3430 fs/jbd2/commit.c:1019
 kjournald2+0x268/0x490 fs/jbd2/journal.c:213
 kthread+0x262/0x280 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30

value changed: 0x0000000000000000 -> 0xffff888104b49900

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 345 Comm: jbd2/sda1-8 Tainted: G        W         5.15.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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