Re: [PATCH 3/6] btrfs: introduce try-lock semantics for exclusive op start

[David Sterba <dsterba@suse.cz>]

On Thu, May 27, 2021 at 03:43:46PM +0800, Anand Jain wrote:
> On 21/05/2021 20:06, David Sterba wrote:
>   Nit:
>   This function implements a conditional lock. But the function name
>   misleads to some operation similar to spin_trylock() or
>   mutex_trylock(). How about btrfs_exclop_start_cond_lock() instead?

The semantics is same as spin_trylock so it's named like it. Try lock is
a conditional lock so I would not want to cause confusion by using
another naming scheme.

https://elixir.bootlin.com/linux/latest/source/include/linux/spinlock_api_smp.h#L86

static inline int __raw_spin_trylock(raw_spinlock_t *lock)
{
	preempt_disable();
	if (do_raw_spin_trylock(lock)) {
		spin_acquire(&lock->dep_map, 0, 1, _RET_IP_);
		return 1;
	}
	preempt_enable();
	return 0;
}

bool btrfs_exclop_start_try_lock(struct btrfs_fs_info *fs_info,
                                enum btrfs_exclusive_operation type)
{
       spin_lock(&fs_info->super_lock);
       if (fs_info->exclusive_operation == type)
               return true;

       spin_unlock(&fs_info->super_lock);
       return false;
}

The code flow is the same.