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

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Message-ID: <Pine.LNX.4.64.0909301040250.16283@cobra.newdream.net>
Date:	Wed, 30 Sep 2009 10:41:55 -0700 (PDT)
From:	Sage Weil <sage@...dream.net>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	yehuda@...dream.net
Subject: Re: [PATCH 03/21] ceph: client types

On Tue, 29 Sep 2009, Andrew Morton wrote:

> 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?

Right.  Would I need an smb_mb() or something in it's place?



> > +
> > +/* 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

Yep!

> > +/*
> > + * 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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> 
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