linux-kernel - Re: [PATCH v2 04/16] mm: Change do_vmi_align

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Message-ID: <20230620122619.GA2934656@google.com>
Date:   Tue, 20 Jun 2023 21:26:19 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        maple-tree@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Peng Zhang <zhangpeng.00@...edance.com>
Subject: Re: [PATCH v2 04/16] mm: Change do_vmi_align_munmap() side tree index

Hello Liam,

On (23/06/12 16:39), Liam R. Howlett wrote:
[..]
> @@ -2450,17 +2452,17 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
>  #if defined(CONFIG_DEBUG_VM_MAPLE_TREE)
>  	/* Make sure no VMAs are about to be lost. */
>  	{
> -		MA_STATE(test, &mt_detach, start, end - 1);
> +		MA_STATE(test, &mt_detach, 0, 0);
>  		struct vm_area_struct *vma_mas, *vma_test;
>  		int test_count = 0;
>  
>  		vma_iter_set(vmi, start);
>  		rcu_read_lock();
> -		vma_test = mas_find(&test, end - 1);
> +		vma_test = mas_find(&test, count - 1);
>  		for_each_vma_range(*vmi, vma_mas, end) {
>  			BUG_ON(vma_mas != vma_test);
>  			test_count++;
> -			vma_test = mas_next(&test, end - 1);
> +			vma_test = mas_next(&test, count - 1);
>  		}
>  		rcu_read_unlock();
>  		BUG_ON(count != test_count);

Something isn't quite working, I'm hitting BUG_ON(vma_mas != vma_test)

[    8.156437] ------------[ cut here ]------------
[    8.160473] kernel BUG at mm/mmap.c:2439!
[    8.163894] invalid opcode: 0000 [#1] PREEMPT SMP PTI

RIP: 0010:do_vmi_align_munmap+0x489/0x8a0

[    8.207867] Call Trace:
[    8.208463]  <TASK>
[    8.209018]  ? die+0x32/0x80
[    8.209709]  ? do_trap+0xd2/0x100
[    8.210520]  ? do_vmi_align_munmap+0x489/0x8a0
[    8.211576]  ? do_vmi_align_munmap+0x489/0x8a0
[    8.212639]  ? do_error_trap+0x94/0x110
[    8.213549]  ? do_vmi_align_munmap+0x489/0x8a0
[    8.214581]  ? exc_invalid_op+0x49/0x60
[    8.215494]  ? do_vmi_align_munmap+0x489/0x8a0
[    8.216576]  ? asm_exc_invalid_op+0x16/0x20
[    8.217562]  ? do_vmi_align_munmap+0x489/0x8a0
[    8.218626]  do_vmi_munmap+0xc7/0x120
[    8.219494]  __vm_munmap+0xaa/0x1c0
[    8.220370]  __x64_sys_munmap+0x17/0x20
[    8.221275]  do_syscall_64+0x34/0x80
[    8.222165]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
[    8.223359] RIP: 0033:0x7fdb0e2fca97
[    8.224224] Code: ff ff ff ff c3 66 0f 1f 44 00 00 f7 d8 89 05 20 28 01 00 48 c7 c0 ff ff ff ff c3 0f 1f 84 00 00 00 00 00 b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8d 0d f9 27 01 00 f7 d8 89 01 48 83
[    8.228432] RSP: 002b:00007ffd15458348 EFLAGS: 00000202 ORIG_RAX: 000000000000000b
[    8.230175] RAX: ffffffffffffffda RBX: 0000562081a347b0 RCX: 00007fdb0e2fca97
[    8.231833] RDX: 0000000000000002 RSI: 0000000000004010 RDI: 00007fdb0e2d5000
[    8.233513] RBP: 00007ffd154584d0 R08: 0000000000000000 R09: 0000562081a3fd30
[    8.235178] R10: 0000562081a3fd18 R11: 0000000000000202 R12: 00007ffd15458388
[    8.236861] R13: 00007ffd15458438 R14: 00007ffd15458370 R15: 0000562081a347b0