Re: [PATCH] btrfs: relax dev_replace rwsem usage on scrub with rst

[Johannes Thumshirn <Johannes.Thumshirn@wdc.com>]

On 14.08.24 16:14, Filipe Manana wrote:
> 
> And, how actually does this patch fixes the double locking problem?
> 
> Isn't the problem that the replace code ends calling btrfs_map_block()
> while holding a read lock on the semaphore and then btrfs_map_block()
> does a read lock on it again?
> 
> I would suggest a different fix:
> 
> Make the device replace code store a pointer (or pid) of to the task
> running device replace, and at btrfs_map_block() don't take the
> semaphore if "current" matches that pointer/pid.
> 
> Wouldn't that work? Seems safe and simple to me.

 From the first test, this seems to work. At least I don't get a lockdep 
splat anymore.

I'll give it some more test time and then I'll submit the patch.

Thanks,
	Johannes