Re: [PATCH] Improve buffered streaming write ordering

[Christoph Hellwig <hch@infradead.org>]

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.
> 
> Opinions?  Andrew, as someone who often weighs in on fs and mm issues,
> what do you think?  My preference would be to make the change to
> mm/page-writeback.c, controlled by a flag which ext4 would set be set
> by fs/ext4 before it calls write_cache_pages().

I agree.  But I'm still not quite sure if that requirement is unique to
ext4 anyway.  Give me some time to dive into the writeback code again,
haven't been there for quite a while.