Re: [RFC PATCH] filelock: new helper: vfs_file_has_locks

From: Xiubo Li <xiubli@redhat.com>
To: Jeff Layton <jlayton@kernel.org>, chuck.lever@oracle.com
Cc: linux-fsdevel@vger.kernel.org, ceph-devel@vger.kernel.org,
	Christoph Hellwig <hch@infradead.org>
Subject: Re: [RFC PATCH] filelock: new helper: vfs_file_has_locks
Date: Wed, 16 Nov 2022 19:16:15 +0800	[thread overview]
Message-ID: <4fac935b-8e33-2202-48c2-80bdfddc074e@redhat.com> (raw)
In-Reply-To: <969b751761988e75b11a75b1f44171305019711a.camel@kernel.org>


On 16/11/2022 18:55, Jeff Layton wrote:
> On Wed, 2022-11-16 at 14:49 +0800, Xiubo Li wrote:
>> On 15/11/2022 22:40, Jeff Layton wrote:
>>
...
>>> +	spin_lock(&ctx->flc_lock);
>>> +	ret = !list_empty(&ctx->flc_posix) || !list_empty(&ctx->flc_flock);
>>> +	spin_unlock(&ctx->flc_lock);
>> BTW, is the spin_lock/spin_unlock here really needed ?
>>
> We could probably achieve the same effect with barriers, but I doubt
> it's worth it. The flc_lock only protects the lists in the
> file_lock_context, so it should almost always be uncontended.
>
I just see some other places where are also checking this don't use the 
spin lock.

Thanks,

- Xiubo

>>> +	return ret;
>>> +}
>>> +EXPORT_SYMBOL_GPL(vfs_inode_has_locks);
>>> +
>>>    #ifdef CONFIG_PROC_FS
>>>    #include <linux/proc_fs.h>
>>>    #include <linux/seq_file.h>
>>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>>> index e654435f1651..d6cb42b7e91c 100644
>>> --- a/include/linux/fs.h
>>> +++ b/include/linux/fs.h
>>> @@ -1170,6 +1170,7 @@ extern int locks_delete_block(struct file_lock *);
>>>    extern int vfs_test_lock(struct file *, struct file_lock *);
>>>    extern int vfs_lock_file(struct file *, unsigned int, struct file_lock *, struct file_lock *);
>>>    extern int vfs_cancel_lock(struct file *filp, struct file_lock *fl);
>>> +bool vfs_inode_has_locks(struct inode *inode);
>>>    extern int locks_lock_inode_wait(struct inode *inode, struct file_lock *fl);
>>>    extern int __break_lease(struct inode *inode, unsigned int flags, unsigned int type);
>>>    extern void lease_get_mtime(struct inode *, struct timespec64 *time);
>> All the others LGTM.
>>
>> Thanks.
>>
>> - Xiubo
>>
>>
> Thanks. I'll re-post it "officially" in a bit and will queue it up for
> v6.2.