Re: [PATCH 1/3] block_write_full_page: Use synchronous writes for WBC_SYNC_ALL writebacks

[Theodore Tso <tytso@mit.edu>]

On Tue, Apr 07, 2009 at 12:23:13AM -0700, Andrew Morton wrote:
> 
> I think the number of different greps which was needed to find all the
> above was excessive.  Too many levels of wrappers and helpers.

This is true not only for the block I/O code, it's true also for the
page writeback code --- have you ever tried creating a call tree that
traces all of the descendents of sync_inode()?

One of these days when I have a spare week (hah!), I'd love to create
a huge chart of all of the callers into the various wrapper functions
of the page writeback paths, figure out who needs what, and then
collapse the rest.

> > It looks like a good candidate for WRITE_SYNC_PLUG instead,

Yeah, what we'll need to do now that we have the difference between
WRITE_SYNC and WRITE_SYNC_PLUG is to have a way of signalling
(probably via yet another wbc flag) that we want WRITE_SYNC_PLUG and
not WRITE_SYNC, and that the top-level caller of this whole mess will
be responsible for issuing the unplug.  I'll try to get something
whipped up.

						- Ted