Re: [PATCH 1/4] xfs: fix log recovery transaction item reordering

[Mark Tinguely <tinguely@sgi.com>]

On 06/04/13 21:09, Dave Chinner wrote:
> From: Dave Chinner<dchinner@redhat.com>
>
> There are several constraints that inode allocation and unlink
> logging impose on log recovery. These all stem from the fact that
> inode alloc/unlink are logged in buffers, but all other inode
> changes are logged in inode items. Hence there are ordering
> constraints that recovery must follow to ensure the correct result
> occurs.
>
> As it turns out, this ordering has been working mostly by chance
> than good management. The existing code moves all buffers except
> cancelled buffers to the head of the list, and everything else to
> the tail of the list. The problem with this is that is interleaves
> inode items with the buffer cancellation items, and hence whether
> the inode item in an cancelled buffer gets replayed is essentially
> left to chance.
>
> Further, this ordering causes problems for log recovery when inode
> CRCs are enabled. It typically replays the inode unlink buffer long before
> it replays the inode core changes, and so the CRC recorded in an
> unlink buffer is going to be invalid and hence any attempt to
> validate the inode in the buffer is going to fail. Hence we really
> need to enforce the ordering that the inode alloc/unlink code has
> expected log recovery to have since inode chunk de-allocation was
> introduced back in 2003...
>
> Signed-off-by: Dave Chinner<dchinner@redhat.com>

Looks good.

Reviewed-by: Mark Tinguely <tinguely@sgi.com>

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