On Tue, Feb 20, 2018 at 08:44:57PM +0800, Anand Jain wrote:
>
>
> On 02/20/2018 07:40 PM, Nikolay Borisov wrote:
> > Patch 11ac3f1da5fd ("btrfs: log, when replace, is canceled by the user")
> > added a new btrfs_info call with a couple of btrfs_dev_name() args. This
> > is wrong since the latter require being called in rcu read side
> > critical section. Fix it by instead calling btrfs_info_in_rcu. This
> > fixes the following splat:
> >
> > =============================
> > WARNING: suspicious RCU usage
> > 4.16.0-rc2-nbor #463 Not tainted
> > -----------------------------
> > fs/btrfs/dev-replace.c:318 suspicious rcu_dereference_check() usage!
> >
> > other info that might help us debug this:
> >
> > rcu_scheduler_active = 2, debug_locks = 1
> > 1 lock held by btrfs/5698:
> > #0: (&fs_info->dev_replace.lock_finishing_cancel_unmount){+.+.}, at: [<00000000942cb4ee>] btrfs_dev_replace_cancel+0xac/0x3f0
> >
> > stack backtrace:
> > CPU: 2 PID: 5698 Comm: btrfs Not tainted 4.16.0-rc2-nbor #463
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
> > Call Trace:
> > dump_stack+0x85/0xc9
> > lockdep_rcu_suspicious+0x123/0x170
> > btrfs_dev_name.part.1+0x6d/0x80
> > btrfs_dev_replace_cancel+0x330/0x3f0
> > btrfs_ioctl+0x2751/0x65b0
> > ? debug_check_no_locks_freed+0x290/0x290
> > ? trace_hardirqs_on_caller+0x400/0x570
> > ? trace_hardirqs_on+0xd/0x10
> > ? btrfs_ioctl_get_supported_features+0x30/0x30
> > ? __handle_mm_fault+0x1aca/0x3230
> > ? lock_downgrade+0x650/0x650
> > ? trace_hardirqs_on+0xd/0x10
> > ? mem_cgroup_commit_charge+0xc0/0xdd0
> > ? _raw_spin_unlock+0x27/0x40
> > ? __handle_mm_fault+0x1aca/0x3230
> > ? lock_downgrade+0x650/0x650
> > ? vm_insert_page+0x650/0x650
> > ? __vma_link_rb+0x125/0x1d0
> > do_vfs_ioctl+0x184/0xf00
> > ? do_vfs_ioctl+0x184/0xf00
> > ? lock_downgrade+0x650/0x650
> > ? ioctl_preallocate+0x1a0/0x1a0
> > ? up_read+0x1f/0x40
> > ? __do_page_fault+0x5c6/0xb30
> > ? SyS_brk+0x412/0x5f0
> > ? mm_fault_error+0x2e0/0x2e0
> > SyS_ioctl+0x41/0x70
> > ? do_vfs_ioctl+0xf00/0xf00
> > do_syscall_64+0x19d/0x5d0
> > entry_SYSCALL_64_after_hwframe+0x42/0xb7
> >
> > Fixes: 11ac3f1da5fd ("btrfs: log, when replace, is canceled by the user")
> > Signed-off-by: Nikolay Borisov <nborisov@xxxxxxxx>
>
> I notice too. Thanks Nikolay for the fix.
I'll fold the fix into the original patch.
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