linux-kernel - Re: upstream test error: BUG: using smp_processor_id() in preemptible code in ext4_mb_new

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Date:   Fri, 12 Jun 2020 22:20:35 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     Greg KH <gregkh@...uxfoundation.org>, adilger.kernel@...ger.ca,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, tytso@....edu
Cc:     syzbot <syzbot+0113b9be6667b5b50840@...kaller.appspotmail.com>
Subject: Re: upstream test error: BUG: using smp_processor_id() in preemptible
 code in ext4_mb_new_blocks

> I am seeing this all over the place on Linus's tree right now:
> 
> [  +0.008563] BUG: using smp_processor_id() in preemptible [00000000] code: systemd/1
> [  +0.000011] caller is ext4_mb_new_blocks+0x2ac/0xc10
> [  +0.000002] CPU: 31 PID: 1 Comm: systemd Not tainted 5.7.0-14371-g25ae6195a4c7 #66
> [  +0.000002] Hardware name: Micro-Star International Co., Ltd. MS-7C59/Creator TRX40 (MS-7C59), BIOS 1.50 05/13/2020
> [  +0.000001] Call Trace:
> [  +0.000008]  dump_stack+0x57/0x70
> [  +0.000004]  debug_smp_processor_id.cold+0x4e/0x53
> [  +0.000001]  ext4_mb_new_blocks+0x2ac/0xc10
> [  +0.000004]  ? ext4_find_extent+0x3e8/0x450
> [  +0.000002]  ext4_ext_map_blocks+0x9f6/0x1b10
> [  +0.000003]  ? ext4_mark_iloc_dirty+0x60f/0xa50
> [  +0.000003]  ? __ext4_journal_get_write_access+0x2d/0x70
> [  +0.000004]  ext4_map_blocks+0x119/0x5a0
> [  +0.000004]  ext4_getblk+0x66/0x1c0
> [  +0.000003]  ext4_bread+0x26/0xc0
> [  +0.000002]  ext4_append+0x49/0xe0
> [  +0.000002]  ext4_mkdir+0x233/0x450
> [  +0.000005]  vfs_mkdir+0x11d/0x1b0
> [  +0.000003]  do_mkdirat+0x92/0x130
> [  +0.000004]  do_syscall_64+0x43/0x80
> [  +0.000004]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [  +0.000003] RIP: 0033:0x7fef3df7a72b
> [  +0.000001] Code: Bad RIP value.
> [  +0.000001] RSP: 002b:00007ffdb4eba0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000053
> [  +0.000003] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fef3df7a72b
> [  +0.000001] RDX: 0000000000000000 RSI: 00000000000001c0 RDI: 0000563b11cf26e0
> [  +0.000001] RBP: 0000563b11cf2731 R08: 000000000000000d R09: 0000000000000002
> [  +0.000000] R10: 11175e4331068ed5 R11: 0000000000000246 R12: 0000563b11cf26e0
> [  +0.000002] R13: 00007fef3e019c20 R14: 00007ffdb4eba0f0 R15: 8421084210842109
> 
> Just a constant stream of them.
> 
> There's a few other fun:
> 
> [  +0.453222] BUG: unable to handle page fault for address: ffffb59cc2719000
> [  +0.000004] #PF: supervisor write access in kernel mode
> [  +0.000001] #PF: error_code(0x000b) - reserved bit violation
> 
> messages at times, but I don't think that's an ext4 issue, but rather
> something in the sound stack...
> 
> EXT4 developers, any hints/patches to try?
> 

Below patch should fix the ext4 issue coming from ext4_mb_new_blocks().

https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git/commit/?h=dev&id=811985365378df01386c3cfb7ff716e74ca376d5

Not sure about the second one though.

-ritesh