Re: [PATCH 2/3] xfs: Don't issue buffer IO direct from AIL push

[Dave Chinner <david@fromorbit.com>]

On Fri, Jan 08, 2010 at 06:07:19AM -0500, Christoph Hellwig wrote:
> > +/*
> > + * If a delwri buffer needs to be pushed before it has aged out, then
> > + * promote it to the head of the delwri queue so that it will be flushed
> > + * on the next xfsbufd run.
> > + */
> > +void
> > +xfs_buf_delwri_promote(
> > +	xfs_buf_t	*bp)
> > +{
> > +	struct list_head *dwq = &bp->b_target->bt_delwrite_queue;
> > +	spinlock_t	*dwlk = &bp->b_target->bt_delwrite_lock;
> > +	long		age = xfs_buf_age_centisecs * msecs_to_jiffies(10) + 1;
> > +
> > +	spin_lock(dwlk);
> > +	ASSERT(bp->b_flags & XBF_DELWRI);
> > +	ASSERT(bp->b_flags & _XBF_DELWRI_Q);
> > +	list_del(&bp->b_list);
> > +	list_add(&bp->b_list, dwq);
> > +	bp->b_queuetime = jiffies - age;
> > +	spin_unlock(dwlk);
> 
> Sorry for the nitpicking, but:
> 
>  a) can you use the struct types instead of the typedefs where possible?

Sure - I missed that one when I went back over this patch after a
c'n'p to create the function.

>  b) second the pointer to spinlock style used here like in some other
>     buf code is rather odd.  What about this instead:
> 
> void
> xfs_buf_delwri_promote(
> 	struct xfs_buf		*bp)
> {
> 	struct xfs_buftarg	*target = bp->b_target;
> 
> 	spin_lock(&target->bt_delwrite_lock);
> 	ASSERT(bp->b_flags & XBF_DELWRI);
> 	ASSERT(bp->b_flags & _XBF_DELWRI_Q);
> 
> 	list_move(&bp->b_list, &target->bt_delwrite_queue);
> 	bp->b_queuetime = jiffies -
> 			  xfs_buf_age_centisecs * msecs_to_jiffies(10) - 1;
> 	spin_unlock(&target->bt_delwrite_lock);
> }

Yup, will change.

> Also the queuetime calculation could use some comments.

OK, will do.

> >  extern void xfs_wait_buftarg(xfs_buftarg_t *);
> >  extern int xfs_setsize_buftarg(xfs_buftarg_t *, unsigned int, unsigned int);
> >  extern int xfs_flush_buftarg(xfs_buftarg_t *, int);
> > +
> > +/*
> > + * run the xfsbufd on demand to age buffers. Use in combination with
> > + * xfs_buf_delwri_promote() to flus delayed write buffers efficiently.
> > + */
> > +static inline void xfs_flush_buftarg_delwri(xfs_buftarg_t *btp)
> > +{
> > +	wake_up_process(btp->bt_task);
> > +}
> 
> The function name is extremly misleading.  It's an xfsbufd wakeup, so it
> should be named like that.  In doubt I'd just opencode the
> wake_up_process call instead.

OK, I just didn't want to be digging deep into the buftarg structure
in places that don't really know about it.

> The changes to the various log items look good, especially as we bring
> some more commonality into the various items.
> 
> 
> You removed the only call to trace_xfs_inode_item_push, so you might
> aswell remove the trace point declaration, too.

Will do.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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