[LEDE-DEV] "block" fstools wishlist

[Karl Palsson]

Listing out a few things I've found with fstools package
(Version: 2016-05-17-db5d39d48b9d9a77565015c1aafb3ef0d2925f02)
I'm mostly still working on openwrt CC branch, but the issues
_seem_ to be fstools related, not kernel related, though I'm
happy to retest if necessary. Some of these I've discussed on irc
with blogic and jow, others just here, posting them here for
posterity as they're bigger than quick fixes on IRC. Further,
this is largely an area I'm not really comfortable trying to hack
up patches, they need to follow the style and direction of the
project more than just my specific needs, so I can't post patches
for any of these.

* block mount mounts _and_ turns swap on.  block umount only unmounts.  Shouldn't it swapoff as well?

* "block" anything can't have it's output captured.  The checks in libubox: ulog.c:: ulog_defaults() detect the attempt at capturing the output as a !tty and write to syslog instead.  

* block doesn't handle hotplug.  This is probably the biggest thing. This overlaps with the old and unmaintained "mountd" package, which blogic expressed interesting destroying/merging/combining with "fstools"  This doesn't seem to be a problem for usb sticks, because the removal of the stick removes the entire device node well.  However, an SD card in a slot maintains a /dev/sda entry even after the card is removed.  "block info" will fail to see new block details if a partition was mounted, or as activated swap, and swap and mounts are not turned off when the card is removed.

I wrote about various trials and tribulations with mountd vs
block here
https://lists.openwrt.org/pipermail/openwrt-devel/2016-February/039798.html
and resolved that I would simply poll "block info" every couple
of seconds. Unfortunately, that ended up being rather noticeable
CPU load, so I'm still looking for neat ways of handling sdcards,
and while mountd noticed disk changes, it failed at reliably
mounting/unmounting, and most importantly, was and is clearly
regarded as "not the right way" going forward.

Desktop linux mostly solves this with udisks/udisks2, and at the moment, something functionally equivalent is rather missing from the lede user space world.  

Cheers,
Karl P
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