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BUG: KCSAN: data-race in ext4_mb_scan_group / mb_mark_used

read-write to 0xffff888100456014 of 4 bytes by task 3660 on cpu 1:
 mb_mark_used+0x138/0xb10 fs/ext4/mballoc.c:2134
 ext4_mb_use_best_found+0xf5/0x2c0 fs/ext4/mballoc.c:2216
 ext4_mb_check_limits fs/ext4/mballoc.c:2280 [inline]
 ext4_mb_complex_scan_group+0x7d2/0x840 fs/ext4/mballoc.c:2596
 __ext4_mb_scan_group fs/ext4/mballoc.c:2664 [inline]
 ext4_mb_scan_group+0xcbf/0xf10 fs/ext4/mballoc.c:2955
 ext4_mb_scan_groups_linear fs/ext4/mballoc.c:1146 [inline]
 ext4_mb_scan_groups fs/ext4/mballoc.c:1180 [inline]
 ext4_mb_regular_allocator+0x70a/0x15e0 fs/ext4/mballoc.c:3026
 ext4_mb_new_blocks+0x800/0x2080 fs/ext4/mballoc.c:6285
 ext4_ext_map_blocks+0xff5/0x38a0 fs/ext4/extents.c:4383
 ext4_map_create_blocks fs/ext4/inode.c:609 [inline]
 ext4_map_blocks+0x5ee/0xd00 fs/ext4/inode.c:811
 ext4_getblk+0x114/0x510 fs/ext4/inode.c:978
 ext4_bread+0x28/0x110 fs/ext4/inode.c:1041
 ext4_append+0x16e/0x2b0 fs/ext4/namei.c:83
 ext4_init_new_dir+0xec/0x180 fs/ext4/namei.c:2982
 ext4_mkdir+0x31f/0x740 fs/ext4/namei.c:3021
 vfs_mkdir+0x213/0x340 fs/namei.c:4366
 do_mkdirat+0x132/0x3f0 fs/namei.c:4399
 __do_sys_mkdirat fs/namei.c:4416 [inline]
 __se_sys_mkdirat fs/namei.c:4414 [inline]
 __x64_sys_mkdirat+0x4c/0x60 fs/namei.c:4414
 x64_sys_call+0x2b7/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:259
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888100456014 of 4 bytes by task 3658 on cpu 0:
 ext4_mb_good_group_nolock fs/ext4/mballoc.c:2759 [inline]
 ext4_mb_scan_group+0x470/0xf10 fs/ext4/mballoc.c:2934
 ext4_mb_scan_groups_linear fs/ext4/mballoc.c:1146 [inline]
 ext4_mb_scan_groups fs/ext4/mballoc.c:1180 [inline]
 ext4_mb_regular_allocator+0x70a/0x15e0 fs/ext4/mballoc.c:3026
 ext4_mb_new_blocks+0x800/0x2080 fs/ext4/mballoc.c:6285
 ext4_ext_map_blocks+0xff5/0x38a0 fs/ext4/extents.c:4383
 ext4_map_create_blocks fs/ext4/inode.c:609 [inline]
 ext4_map_blocks+0x5ee/0xd00 fs/ext4/inode.c:811
 ext4_getblk+0x114/0x510 fs/ext4/inode.c:978
 ext4_bread+0x28/0x110 fs/ext4/inode.c:1041
 ext4_append+0x16e/0x2b0 fs/ext4/namei.c:83
 ext4_init_new_dir+0xec/0x180 fs/ext4/namei.c:2982
 ext4_mkdir+0x31f/0x740 fs/ext4/namei.c:3021
 vfs_mkdir+0x213/0x340 fs/namei.c:4366
 do_mkdirat+0x132/0x3f0 fs/namei.c:4399
 __do_sys_mkdirat fs/namei.c:4416 [inline]
 __se_sys_mkdirat fs/namei.c:4414 [inline]
 __x64_sys_mkdirat+0x4c/0x60 fs/namei.c:4414
 x64_sys_call+0x2b7/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:259
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000007de -> 0x000007dd

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3658 Comm: syz-executor.5 Not tainted 6.16.0-syzkaller-11241-g186f3edfdd41 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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