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Date: Mon, 18 Nov 2013 03:04:49 -0800
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [RFC PATCH 4/4] xfs: implement parallism quota check
Message-ID: <20131118110449.GB1304@infradead.org>
References: <5281F527.3040200@oracle.com>
	<20131115172626.GD16942@infradead.org>
	<5288BE14.1050302@oracle.com>
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To: Jeff Liu <jeff.liu@oracle.com>
Cc: Christoph Hellwig <hch@infradead.org>, "xfs@oss.sgi.com" <xfs@oss.sgi.com>

On Sun, Nov 17, 2013 at 09:01:08PM +0800, Jeff Liu wrote:
> On 11/16 2013 01:26 AM, Christoph Hellwig wrote:
> > As Dave pointed out this really should be xfs_bukstat_ag.  But looking
> > at the code you're almost 90% there anyway.
> One main reason I did not make a per ag bulkstat is because bulkstat() will
> skip an allocation group if read agi buffer failed, i.e,
> 
> while (XFS_BULKSTAT_UBLEFT(ubleft) && agno < mp->m_sb.sb_agcount) {
> 	cond_resched();
> 	error = xfs_ialloc_read_agi(mp, NULL, agno, &agbp);
> 	if (error) {
> 		/*
> 		 * Skip this allocation group and go to the next one.
> 		 */
> 		agno++;
>                 agino = 0;
> 		continue;
> 	}
> 	....
> }
>
> Should it capture this issue and drop a warning in this case?

I've been thinking hard about this, but I can't really see any reason
why we would skip an AG instead of propagating the error.  The only
error xfs_ialloc_read_agi can return is an I/O error from reading
the buffer from disk, and we'd really want to propagate that sort
of I/O errror.  I'd suggest a patch at the beginning of the series
to just change that behavior for all the two places in bulkstat that
call xfs_ialloc_read_agi.  None of the other callers seem to behave
this way either.

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