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SubjectRe: [patch 05/27] fs: brlock vfsmount_lock
On Sat, Apr 25, 2009 at 11:20:25AM +1000, npiggin@suse.de wrote:

[overall: sane idea, but...]

> +void vfsmount_read_lock(void)
> +{
> + spinlock_t *lock;
> +
> + lock = &get_cpu_var(vfsmount_lock);
> + spin_lock(lock);
> +}
> +
> +void vfsmount_read_unlock(void)
> +{
> + spinlock_t *lock;
> +
> + lock = &__get_cpu_var(vfsmount_lock);
> + spin_unlock(lock);
> + put_cpu_var(vfsmount_lock);
> +}

These might be hot enough to be worth inlining, at least in fs/namei.c
users. Or not - really needs testing.

> @@ -68,9 +113,9 @@ static int mnt_alloc_id(struct vfsmount
>
> retry:
> ida_pre_get(&mnt_id_ida, GFP_KERNEL);
> - spin_lock(&vfsmount_lock);
> + vfsmount_write_lock();
> res = ida_get_new(&mnt_id_ida, &mnt->mnt_id);
> - spin_unlock(&vfsmount_lock);
> + vfsmount_write_unlock();

Yuck. _Really_ an overkill here.

> static void mnt_free_id(struct vfsmount *mnt)
> {
> - spin_lock(&vfsmount_lock);
> + vfsmount_write_lock();
> ida_remove(&mnt_id_ida, mnt->mnt_id);
> - spin_unlock(&vfsmount_lock);
> + vfsmount_write_unlock();
> }

Ditto.

Missing: description of when we need it for read/when we need it for write.


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