[Cluster-devel] [PATCH] GFS2: Add a next-resource-group pointer to resource groups
Andrew Price
anprice at redhat.com
Tue Jan 12 15:23:39 UTC 2016
On 12/01/16 13:30, Andreas Gruenbacher wrote:
> Is it guaranteed that the kernel will never set the new rg_skip field
> if it hasn't verified that the next resource group is where it thinks
> it is?
No, but rg_skip is set from the ri_addr of the next resource group in
the rindex and gfs2 generally trusts the rindex so if it's corrupt then
there'll be other problems down the line.
> Otherwise we could end up with incorrect fsck "hints" for
> corrupted filesystems, which would make things worse.
I don't think it would make things worse. fsck.gfs2 will be able to
check whether the rg_skip field is correct by checking it against the
rindex and whether there's an rgrp where it's pointing (and checking
that it's within a sensible range). Before, we only had the rindex and
the rgrp header to check against each other but now we have a third factor.
That said, the fsck.gfs2 case is only one of the ways this would be
useful. The original plan was to generally reduce dependence on the
rindex, effectively allowing us to iterate over all rgrps without
reading it in. Though I don't recall the specific issue which motivated
it, I can think of cases where it would improve things.
Andy
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