[EXT3/JBD] Periodic journal flush not enough?

[Herbert Xu <herbert@gondor.apana.org.au>]

Hi:

I've encountered a problem with the journal flush timer.  The problem
is that when a filesystem is short on space, relying on a timer-based
flushing mechanism is no longer adequate.  For example, on my P4 2GHz
I can trigger an ENOSPC error by doing

while :; do echo test > a; [ -s a ] || break; rm a; done; echo Out of space

on an ext3 file system with 12Mb of free space using the usual 5s
journal flush timer.

Of course, when you extend the flushing period as you do with laptop-mode,
this problem becomes a lot worse.

So would it be possible to have the flushing activated on demand?

Thanks,
-- 
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Email:  Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
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