Re: [PATCH v2 3/3] xfs_repair: try to fill the AGFL before we fix the freelist

[Christoph Hellwig <hch@infradead.org>]

On Wed, Jul 08, 2020 at 08:34:55AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> In commit 9851fd79bfb1, we added a slight amount of slack to the free
> space btrees being reconstructed so that the initial fix_freelist call
> (which is run against a totally empty AGFL) would never have to split
> either free space btree in order to populate the free list.
> 
> The new btree bulk loading code in xfs_repair can re-create this
> situation because it can set the slack values to zero if the filesystem
> is very full.  However, these days repair has the infrastructure needed
> to ensure that overestimations of the btree block counts end up on the
> AGFL or get freed back into the filesystem at the end of phase 5.
> 
> Fix this problem by reserving extra blocks in the bnobt reservation, and
> checking that there are enough overages in the bnobt/cntbt fakeroots to
> populate the AGFL with the minimum number of blocks it needs to handle a
> split in the bno/cnt/rmap btrees.
> 
> Note that we reserve blocks for the new bnobt/cntbt/AGFL at the very end
> of the reservation steps in phase 5, so the extra allocation should not
> cause repair to fail if it can't find blocks for btrees.
> 
> Fixes: 9851fd79bfb1 ("repair: AGFL rebuild fails if btree split required")
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> Reviewed-by: Brian Foster <bfoster@redhat.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>