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BUG: KCSAN: data-race in proc_cgroup_show / stop_this_handle

write to 0xffff8880233ac02c of 4 bytes by task 18939 on cpu 0:
 memalloc_nofs_restore include/linux/sched/mm.h:258 [inline]
 stop_this_handle+0x2ae/0x2f0 fs/jbd2/transaction.c:744
 jbd2_journal_stop+0x573/0x6d0 fs/jbd2/transaction.c:1907
 __ext4_journal_stop+0x99/0x110 fs/ext4/ext4_jbd2.c:127
 ext4_da_write_end+0x5c6/0x760 fs/ext4/inode.c:3117
 generic_perform_write+0x23e/0x3a0 mm/filemap.c:3423
 ext4_buffered_write_iter+0x2e5/0x3e0 fs/ext4/file.c:270
 ext4_file_write_iter+0x47a/0x1060 fs/ext4/file.c:503
 call_write_iter include/linux/fs.h:1901 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x6f0/0x7e0 fs/read_write.c:605
 ksys_write+0xce/0x180 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880233ac02c of 4 bytes by task 4862 on cpu 1:
 proc_cgroup_show+0x3b3/0x6a0 kernel/cgroup/cgroup.c:5846
 proc_single_show+0x84/0x100 fs/proc/base.c:775
 seq_read_iter+0x2ef/0x910 fs/seq_file.c:227
 seq_read+0x221/0x260 fs/seq_file.c:159
 vfs_read+0x154/0x5d0 fs/read_write.c:494
 ksys_read+0xce/0x180 fs/read_write.c:634
 __do_sys_read fs/read_write.c:644 [inline]
 __se_sys_read fs/read_write.c:642 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:642
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 4862 Comm: systemd-journal Not tainted 5.11.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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