Re: [PATCH 1/2] kernfs: replace the mutex in kernfs_iop_permission with a rwlock

[Tejun Heo]

Hello,

On Wed, Dec 02, 2020 at 10:58:36PM +0800, Fox Chen wrote:
> @@ -121,7 +121,7 @@ int kernfs_iop_setattr(struct dentry *dentry, struct 
> iattr *iattr)
>       if (!kn)
>               return -EINVAL;
>  
> -     mutex_lock(&kernfs_mutex);
> +     write_lock(&kn->iattr_rwlock);
>       error = setattr_prepare(dentry, iattr);
>       if (error)
>               goto out;
> @@ -134,7 +134,7 @@ int kernfs_iop_setattr(struct dentry *dentry, struct 
> iattr *iattr)
>       setattr_copy(inode, iattr);
>  
>  out:
> -     mutex_unlock(&kernfs_mutex);
> +     write_unlock(&kn->iattr_rwlock);
>       return error;
>  }

This is putting GFP_KERNEL allocation inside a rwlock. Can you please test
with debug options including LOCKDEP and DEBUG_ATOMIC_SLEEP turned on?

Thanks.

-- 
tejun