You got that backwards. Filesystems do not become community-supported because they are chosen as a default (though if they are common, community members *are* more likely to show an interest in them). It is more that they are very unlikely ever to be chosen as a default by anyone except their originator unless they are already community-supported.
Improving ext4: bigalloc, inline data, and metadata checksums
Posted Dec 3, 2011 18:06 UTC (Sat) by raven667 (subscriber, #5198)
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Reiserfs3 being an example of that, being widely shipped but unsupported and unsupportable by the community leading to more stringent support guidelines for future code acceptance