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BUG: KCSAN: data-race in ext4_mb_good_group / mb_mark_used

read-write to 0xffff88810047f014 of 4 bytes by task 3649 on cpu 0:
 mb_mark_used+0x138/0xb20 fs/ext4/mballoc.c:2065
 ext4_mb_use_best_found+0xf5/0x2a0 fs/ext4/mballoc.c:2147
 ext4_mb_check_limits fs/ext4/mballoc.c:2211 [inline]
 ext4_mb_complex_scan_group+0x7d2/0x840 fs/ext4/mballoc.c:2527
 ext4_mb_regular_allocator+0x1090/0x2300 fs/ext4/mballoc.c:2943
 ext4_mb_new_blocks+0x800/0x2050 fs/ext4/mballoc.c:6215
 ext4_ext_map_blocks+0xfe6/0x3620 fs/ext4/extents.c:4379
 ext4_map_create_blocks fs/ext4/inode.c:520 [inline]
 ext4_map_blocks+0x5ab/0xd00 fs/ext4/inode.c:706
 ext4_getblk+0x114/0x510 fs/ext4/inode.c:853
 ext4_bread+0x28/0x110 fs/ext4/inode.c:916
 ext4_append+0x16e/0x2b0 fs/ext4/namei.c:83
 ext4_init_new_dir+0x144/0x490 fs/ext4/namei.c:2971
 ext4_mkdir+0x31f/0x740 fs/ext4/namei.c:3017
 vfs_mkdir+0x213/0x340 fs/namei.c:4359
 do_mkdirat+0x132/0x3f0 fs/namei.c:4392
 __do_sys_mkdirat fs/namei.c:4409 [inline]
 __se_sys_mkdirat fs/namei.c:4407 [inline]
 __x64_sys_mkdirat+0x4c/0x60 fs/namei.c:4407
 x64_sys_call+0x2be0/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:259
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810047f014 of 4 bytes by task 3658 on cpu 1:
 ext4_mb_good_group+0xbe/0x310 fs/ext4/mballoc.c:2591
 ext4_mb_good_group_nolock fs/ext4/mballoc.c:2713 [inline]
 ext4_mb_regular_allocator+0xc71/0x2300 fs/ext4/mballoc.c:2903
 ext4_mb_new_blocks+0x800/0x2050 fs/ext4/mballoc.c:6215
 ext4_ext_map_blocks+0xfe6/0x3620 fs/ext4/extents.c:4379
 ext4_map_create_blocks fs/ext4/inode.c:520 [inline]
 ext4_map_blocks+0x5ab/0xd00 fs/ext4/inode.c:706
 ext4_getblk+0x114/0x510 fs/ext4/inode.c:853
 ext4_bread+0x28/0x110 fs/ext4/inode.c:916
 ext4_append+0x16e/0x2b0 fs/ext4/namei.c:83
 ext4_init_new_dir+0x144/0x490 fs/ext4/namei.c:2971
 ext4_mkdir+0x31f/0x740 fs/ext4/namei.c:3017
 vfs_mkdir+0x213/0x340 fs/namei.c:4359
 do_mkdirat+0x132/0x3f0 fs/namei.c:4392
 __do_sys_mkdirat fs/namei.c:4409 [inline]
 __se_sys_mkdirat fs/namei.c:4407 [inline]
 __x64_sys_mkdirat+0x4c/0x60 fs/namei.c:4407
 x64_sys_call+0x2be0/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:259
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000006b0 -> 0x000006af

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3658 Comm: syz-executor.5 Not tainted 6.15.0-rc7-syzkaller-00142-g4856ebd99715 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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