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Re: [PATCH 4/5] xfs: limit extsize to size of AGs and/or MAXEXTLEN

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH 4/5] xfs: limit extsize to size of AGs and/or MAXEXTLEN
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 25 Jan 2011 10:37:35 +1100
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20110124090656.GE26744@xxxxxxxxxxxxx>
References: <1295411400-15614-1-git-send-email-david@xxxxxxxxxxxxx> <1295411400-15614-5-git-send-email-david@xxxxxxxxxxxxx> <20110124090656.GE26744@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.20 (2009-06-14)
On Mon, Jan 24, 2011 at 04:06:56AM -0500, Christoph Hellwig wrote:
> On Wed, Jan 19, 2011 at 03:29:59PM +1100, Dave Chinner wrote:
> > +            * Also, for non-realtime files, limit the extent size hint to
> > +            * half the size of the AGs in the filesystem so alignment
> > +            * doesn't result in extents larger than an AG.
> 
> What do we do about the last AG, which potentionally is smaller than the
> others?

Not sure - I didn't actually consider that case because I forgot
about it.

At first glance it doesn't matter because it won't get
selected because the length of the AG is less than the requested
size unless it is the best match. If it is the best match, we can't
do extsize alignment anyway, so it's the same case as any other
allocation without a freespace extent large enough for alignment.

I'll do a bit more analysis, but I think we're OK here.

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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