From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andreas Dilger <adilger@clusterfs.com>
Subject: Re: i_mutex locking in generic_file_splice_write()
Date: Mon, 16 Oct 2006 11:58:08 -0600
Message-ID: <20061016175808.GH6221@schatzie.adilger.int>
References: <20061012125409.40bd1fb1.akpm@osdl.org> <20061013001715.GV6485@ca-server1.us.oracle.com> <20061013074516.GY6515@kernel.dk> <20061013011129.42a757fb.akpm@osdl.org> <20061013081855.GG6515@kernel.dk> <20061013194442.GA2954@ca-server1.us.oracle.com> <20061015180520.GC14399@kernel.dk> <20061015195657.GA13426@ca-server1.us.oracle.com> <20061015200828.GO14399@kernel.dk> <20061015201415.GB13426@ca-server1.us.oracle.com>
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Cc: Jens Axboe <jens.axboe@oracle.com>, Andrew Morton <akpm@osdl.org>,
	linux-fsdevel@vger.kernel.org,
	Michael Halcrow <mhalcrow@us.ibm.com>
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To: Mark Fasheh <mark.fasheh@oracle.com>
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On Oct 15, 2006  13:14 -0700, Mark Fasheh wrote:
> +void inode_double_lock(struct inode *inode1, struct inode *inode2)
> +{
> +	if (!inode1 || !inode2) {
> +		if (inode1)
> +			mutex_lock(&inode1->i_mutex);
> +		else if (inode2)
> +			mutex_lock(&inode2->i_mutex);
> +		return;
> +	}
> +
> +	if (inode1 == inode2) {
> +		mutex_lock(&inode1->i_mutex);

Could be a tiny bit cleaner if you put the "inode1 == inode2" case above:

void inode_double_lock(struct inode *inode1, struct inode *inode2)
{
	if (inode1 == NULL || inode2 == NULL || inode1 == inode2) {
		if (inode1)
			mutex_lock(&inode1->i_mutex);
		else if (inode2)
			mutex_lock(&inode2->i_mutex);
		return;
	}

	if (inode1 < inode2) {
		mutex_lock_nested(&inode1->i_mutex, I_MUTEX_PARENT);
		mutex_lock_nested(&inode2->i_mutex, I_MUTEX_CHILD);
	} else {
		mutex_lock_nested(&inode2->i_mutex, I_MUTEX_PARENT);
		mutex_lock_nested(&inode1->i_mutex, I_MUTEX_CHILD);
	}
}

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.