2008-10-07 14:46:06

by Nick Piggin

[permalink] [raw]
Subject: Re: [PATCH] Improve buffered streaming write ordering

On Wednesday 08 October 2008 00:36, Christoph Hellwig wrote:
> On Tue, Oct 07, 2008 at 09:29:11AM -0400, Theodore Tso wrote:
> > That's true, but there is a lot of code duplication, which means that
> > bugs or changes in write_cache_pages() would need to be fixed in
> > ext4_write_cache_pages(). So another approach that might be better
> > from a long-term code maintenance point of view is to add a flag in
> > struct writeback_control that tells write_cache_pages() not to update
> > those fields, and avoid duplicating approximately 95 lines of code.
> > It means a change in a core mm function, though, so if folks thinks
> > its too ugly, we can make our own copy in fs/ext4.

Heh, funny you should mention that. I was looking at it just the other
day. It's riddled with bugs (some of which supposedly are by-design
circumventing of data integrity).


I'm also looking (in the same thread) at doing a patch to improve fsync
performance and ensure it doesn't get stuck behind concurrent dirtiers
by adding another tag to the radix-tree. Mikulas is also looking at
improving that problem with another method. It would be nice if fsdevel
gurus would participate (I'll send out my patchset when I get it working,
and recap the situation and competing ideas).