How PUFFS should deal with EDQUOT?

[manu%netbsd.org@localhost (Emmanuel Dreyfus)]

Hi

When a PUFFS filesystem enforces quota, a process doing a write over
quota will end frozen in DE+ state.

The problem is that  we have written data in the page cache that is
supposed to go to disk. The code path is a bit complicated, but
basically we go in genfs VOP_PUTPAGE, which leads to genfs_do_io() where
we have a VOP_STRATEGY, which cause PUFFS write. The PUFFS write will
get EDQUOT, but genfs_do_io()  ignores VOP_STRATEGY's return value and
retries forever.

In other words, when flushing the cache, the kernel ignores errors from
the filesystem and runs an endless loop attempting to flush data, during
which the process that did the over quota write is not allowed to
complete exit().

What is the proper way to deal with that? Is it reasonable to wipe the
page cache using puffs_inval_pagecache_node() when write gets a failure?
Any failure? Or just EDQUOT and ENOSPC? Should that happen in libpuffs
or in the filesystem (libperfuse here)?

-- 
Emmanuel Dreyfus
http://hcpnet.free.fr/pubz
manu%netbsd.org@localhost