[PATCH 3/6] writeback: Add tracing to write_cache_pages

[Christoph Hellwig]

On Fri, Jun 04, 2010 at 09:55:25AM +1000, Dave Chinner wrote:
> Add a trace event to the ->writepage loop in write_cache_pages to give
> visibility into how the ->writepage call is changing variables within the
> writeback control structure. Of most interest is how wbc->nr_to_write changes
> from call to call, especially with filesystems that write multiple pages
> in ->writepage.

Looks good, it might be worth to add another tracepoint for ->writepage
from reclaim context so that we can start investigating the cases where
that happens far too often.

Reviewed-by: Christoph Hellwig <hch at lst.de>