Re: [PATCH] xfs: perag initialization should only touch m_ag_max_usable for AG 0

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Thu, Sep 21, 2017 at 07:04:21AM -0700, Christoph Hellwig wrote:
> On Tue, Sep 19, 2017 at 11:10:41AM -0700, Darrick J. Wong wrote:
> > We call __xfs_ag_resv_init to make a per-AG reservation for each AG.
> > This makes the reservation per-AG, not per-filesystem.  Therefore, it
> > is incorrect to adjust m_ag_max_usable for each AG.  Adjust it only
> > when we're reserving AG 0's blocks so that we only do it once per fs.
> 
> This looks correct to me, but I hate how we manipulate a per-mount
> value.  Is there a way we can just move this to the caller?

I'm not sure which caller you're referring to -- if you mean
xfs_ag_resv_init, then we'd still have the "if (pag->agno == 0)
xfs_mod_fdblocks(...)"; and if xfs_fs_reserve_ag_blocks then you'd have
to bubble the two ask values up out of xfs_ag_resv_init, which also
seems like a layering violation.  Modifying fdblocks in
__xfs_ag_resv_init (Dave I think is sharpening his axe on that) smells
kinda funny but it's less code intensive.

<confused>

--D

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