linux-kernel - Re: [PATCH 03/21] ceph: client types

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Date:	Tue, 29 Sep 2009 16:57:58 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Sage Weil <sage@...dream.net>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	yehuda@...dream.net, sage@...dream.net
Subject: Re: [PATCH 03/21] ceph: client types

On Tue, 22 Sep 2009 10:38:31 -0700
Sage Weil <sage@...dream.net> wrote:

> We first define constants, types, and prototypes for the kernel client
> proper.
> 
> A few subsystems are defined separately later: the MDS, OSD, and
> monitor clients, and the messaging layer.
> 
>
> ...
>
> +static inline bool ceph_i_test(struct inode *inode, unsigned mask)
> +{
> +	struct ceph_inode_info *ci = ceph_inode(inode);
> +	bool r;
> +
> +	spin_lock(&inode->i_lock);
> +	r = (ci->i_ceph_flags & mask) == mask;
> +	spin_unlock(&inode->i_lock);
> +	return r;
> +}

I'm not sure that the locking in ceph_i_test() makes much sense.  The
condition we just checked could change one femtosecond after we dropped
the lock, so why take the lock?

> +
> +/* find a specific frag @f */
> +static inline struct ceph_inode_frag *
> +__ceph_find_frag(struct ceph_inode_info *ci, u32 f)
> +{
> +	struct rb_node *n = ci->i_fragtree.rb_node;
> +
> +	while (n) {
> +		struct ceph_inode_frag *frag =
> +			rb_entry(n, struct ceph_inode_frag, node);
> +		int c = frag_compare(f, frag->frag);
> +		if (c < 0)
> +			n = n->rb_left;
> +		else if (c > 0)
> +			n = n->rb_right;
> +		else
> +			return frag;
> +	}
> +	return NULL;
> +}

Please review the entire fs and verify that all inlining decisions were
appropriate.  Unless this function has a single call site, this
decision wasn't appropriate.

And if it _does_ have a single callsite, it should be defined in the
relevant .c file, not in .h

> +/*
> + * choose fragment for value @v.  copy frag content to pfrag, if leaf
> + * exists
> + */
> +extern u32 ceph_choose_frag(struct ceph_inode_info *ci, u32 v,
> +			    struct ceph_inode_frag *pfrag,
> +			    int *found);
> +
>
> ...
>

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