Re: [patch 10/10] fs: brlock vfsmount_lock

[Andi Kleen <andi@firstfloor.org>]

Nick Piggin <npiggin@kernel.dk> writes:

BTW one way to make the slow path faster would be to start sharing
per cpu locks inside a core on SMT at least. The same cores have the same
caches and sharing cache lines is free. That would cut it in half
on a 2x HT system.

> -
>  static int event;
>  static DEFINE_IDA(mnt_id_ida);
>  static DEFINE_IDA(mnt_group_ida);
> +static DEFINE_SPINLOCK(mnt_id_lock);

Can you add a scope comment to that lock? 

> @@ -623,39 +653,43 @@ static inline void __mntput(struct vfsmo
>  void mntput_no_expire(struct vfsmount *mnt)
>  {
>  repeat:
> -	if (atomic_dec_and_lock(&mnt->mnt_count, &vfsmount_lock)) {
> -		if (likely(!mnt->mnt_pinned)) {
> -			spin_unlock(&vfsmount_lock);
> -			__mntput(mnt);
> -			return;
> -		}
> -		atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count);
> -		mnt->mnt_pinned = 0;
> -		spin_unlock(&vfsmount_lock);
> -		acct_auto_close_mnt(mnt);
> -		goto repeat;
> +	if (atomic_add_unless(&mnt->mnt_count, -1, 1))
> +		return;

Hmm that's a unrelated change?

The rest looks all good and quite straight forward

Reviewed-by: Andi Kleen <ak@linux.intel.com>
-Andi
-- 
ak@linux.intel.com -- Speaking for myself only.