semi-stable page writes

Hi everyone,

Are people still annoyed about writes taking unexpectedly long amounts of tme
due to the stable page write patchset?  I'm guessing yes...

I'm close to posting a patchset that (a) gates the wait_on_page_writeback calls
on a flag that you can set in the bdi to indicate that you need stable writes
(which blk_integrity_register will set); (b) (ab)uses a page flag bit (PG_slab)
to indicate that a page is actually being sent out to disk hardware; and (c)
changes the three calls to wait_on_page_writeback()s that were in the original
patchset to only wait if the bit in (b) is set.  Sort of a hack, but it'll fix
some of the latency complaints.

I guess I should let that run overnight, and clean up/mail out the set tomorrow.

--D