Re: Torn page hazard in ginRedoUpdateMetapage()

On Wed, May 2, 2012 at 6:06 PM, Noah Misch <noah@leadboat.com> wrote:
> Can we indeed assume that all support-worthy filesystems align the start of
> every file to a physical sector?  I know little about modern filesystem
> design, but these references leave me wary of that assumption:
>
> http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg14690.html
> http://en.wikipedia.org/wiki/Block_suballocation
>
> If it is a safe assumption, we could exploit it elsewhere.

Not to say whether this is safe or not, but it *is* exploited
elsewhere, as I understand it: the pg_control information, whose
justification for its safety is its small size.  That may point to a
very rare problem with pg_control rather the safety of the assumption
it makes.

--
fdr