JFFS2 is broken

[Alan Cox]

> The problem is that JFFS2 tries to be a good guy and tries its hand at
> GC'ing dirty flash, _from within a write() system call_

That in itself is probably fine, write should only hold the inode lock
for that file

> Unfortunately, there is a problem with this approach. If write() cannot
> find space and now we refuse to GC inside the write and return with
> -ENOSPC, a lot of stock programs may break. I am returning -ENSPC
> because I just didn't take the time to figure out how to return 0, which

One thing you can do here is to wake the gc thread and sleep politely on it

> The only solution, that I think will work, is to find a way to block the
> write() to JFFS2 but allow kernel schedduling to go on. I really don't
> know

Well there are two things there.

1.	You could wake the GC and sleep on it  using sleep/wakeup or
	semaphores

2.	Profile the kernel and find out where it is tight looping. I can't
	see any reason for tight loops except for the compression itself
	so it suggests a code bug.

Finally within the compression loops you can check current->need_resched and
if it is set call schedule() to allow the compression to switch to other
tasks at the point it has used its time slice.

Alan