linux-kernel - Re: [PATCH] fuse: hold i_mutex in fuse_file

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Date:	Wed, 12 Jun 2013 12:04:25 -0700
From:	Anand Avati <avati@...hat.com>
To:	Maxim Patlasov <MPatlasov@...allels.com>
CC:	miklos@...redi.hu, fuse-devel@...ts.sourceforge.net,
	bfoster@...hat.com, linux-kernel@...r.kernel.org, devel@...nvz.org
Subject: Re: [PATCH] fuse: hold i_mutex in fuse_file_fallocate()

On 6/11/13 3:59 AM, Maxim Patlasov wrote:

> -	if (mode & FALLOC_FL_PUNCH_HOLE) {
> +	if (lock_inode)
>   		mutex_lock(&inode->i_mutex);

> +	if (mode & FALLOC_FL_PUNCH_HOLE)
>   		fuse_set_nowrite(inode);
> -	}

Just for clarity, can you make the condition to check 
FALLOC_FL_PUNCH_HOLE and call to fuse_set_nowrite() nested within the 
larger if (lock_inode) { .. } block? fuse_set_nowrite() should not be 
called without i_mutex acquired. The current style of calling 
mutex_lock() and fuse_set_nowrite() in separate conditions can 
potentially cause bugs in the future if they were to get re-ordered due 
to some unrelated patch. Nesting them makes the relation more explicit 
and clear.

Thanks,
Avati

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