Re: [PATCH] cowlinks v2

[Andrew Morton]

Jörn Engel <joern@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> +static long fcntl_setcow(struct file *filp, unsigned long arg)
>  +{
>  +	struct inode *inode = filp->f_dentry->d_inode;
>  +
>  +	spin_lock(&inode->i_lock);
>  +	if (arg)
>  +		inode->i_flags |= S_COWLINK;
>  +	else
>  +		inode->i_flags &= ~S_COWLINK;
>  +	mark_inode_dirty_sync(inode);
>  +	spin_unlock(&inode->i_lock);
>  +	return 0;
>  +}
>  +

i_lock is an innermost lock.  No locks should be taken inside i_lock.

Here, not only is inode_lock being taken inside i_lock but ->dirty_inode
may be called as well, and dirty_inode() may not be called under any
spinlock.

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