From: "J. Bruce Fields" <bfields@fieldses.org>
Subject: Re: [PATCH 1/10] lockd: add new export operation for
	nfsv4/lockd locking
Date: Thu, 14 Dec 2006 18:04:42 -0500
Message-ID: <20061214230442.GB5147@fieldses.org>
References: <11653832602203-git-send-email-bfields@fieldses.org>
	<8eb625184e6025f7f3d081dfe0a805abdd62a068.1165380892.git.bfields@citi.umich.edu>
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Cc: nfs@lists.sourceforge.net, Marc Eshel <eshel@almaden.ibm.com>
To: linux-fsdevel@vger.kernel.org
In-Reply-To: <8eb625184e6025f7f3d081dfe0a805abdd62a068.1165380892.git.bfields@citi.umich.edu>
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By the way, one other issue I think we'll need to resolve:

On Wed, Dec 06, 2006 at 12:34:11AM -0500, J. Bruce Fields wrote:
> +/**
> + * vfs_cancel_lock - file byte range unblock lock
> + * @filp: The file to apply the unblock to
> + * @fl: The lock to be unblocked
> + *
> + * FL_CANCELED is used to cancel blocked requests
> + */
> +int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
> +{
> +	int status;
> +	struct super_block *sb;
> +
> +	fl->fl_flags |= FL_CANCEL;
> +	sb = filp->f_dentry->d_inode->i_sb;
> +	if (sb->s_export_op && sb->s_export_op->lock)
> +		status = sb->s_export_op->lock(filp, F_SETLK, fl);
> +	else
> +		status = posix_unblock_lock(filp, fl);
> +	fl->fl_flags &= ~FL_CANCEL;
> +	return status;
> +}

So we're passing cancel requests to the filesystem by setting an
FL_CANCEL flag in fl_flags and then calling the lock operation.  I think
Trond has said he'd rather keep fl_flags for permanent characteristics
of the lock in question, rather than as a channel for passing arguments
to lock operations.  Also, the GFS patch isn't checking FL_CANCEL, so
that's a bug.

--b.

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