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

From: Christoph Hellwig <hch@infradead.org>
To: Jeff Layton <jlayton@kernel.org>
Cc: chuck.lever@oracle.com, xiubli@redhat.com,
	linux-fsdevel@vger.kernel.org, ceph-devel@vger.kernel.org
Subject: Re: [RFC PATCH] filelock: new helper: vfs_file_has_locks
Date: Tue, 15 Nov 2022 00:54:31 -0800	[thread overview]
Message-ID: <Y3NTx/x2m/kAZyGE@infradead.org> (raw)
In-Reply-To: <20221114140747.134928-1-jlayton@kernel.org>

On Mon, Nov 14, 2022 at 09:07:47AM -0500, Jeff Layton wrote:
> +bool vfs_file_has_locks(struct file *filp)
> +{
> +	struct file_lock_context *ctx;
> +	struct file_lock *fl;
> +	bool ret = false;
> +
> +	ctx = smp_load_acquire(&locks_inode(filp)->i_flctx);
> +	if (!ctx)
> +		return false;
> +
> +	spin_lock(&ctx->flc_lock);
> +	list_for_each_entry(fl, &ctx->flc_posix, fl_list) {
> +		if (fl->fl_file == filp) {
> +			ret = true;
> +			goto out;
> +		}
> +	}
> +	list_for_each_entry(fl, &ctx->flc_flock, fl_list) {
> +		if (fl->fl_file == filp) {
> +			ret = true;
> +			break;
> +		}
> +	}

Maybe a little helper for the list lookup would be nice here:
static inline bool __vfs_file_has_locks(struct file *file)
{
	struct file_lock *fl;

	list_for_each_entry(fl, &ctx->flc_flock, fl_list)
		if (fl->fl_file == filp)
			return true;
	return false;
}

simplifying the check in the caller to:

	ret = __vfs_file_has_locks(&ctx->flc_posix) ||
	      __vfs_file_has_locks(&ctx->flc_flock);

> +EXPORT_SYMBOL(vfs_file_has_locks);

EXPORT_SYMBOL_GPL for any new network-fsy functionality would be nice.