Messages in this thread | | | Date | Wed, 9 Jun 2010 14:09:42 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 1/3] writeback: pay attention to wbc->nr_to_write in write_cache_pages |
| |
On Wed, 9 Jun 2010 10:37:18 +1000 Dave Chinner <david@fromorbit.com> wrote:
> From: Dave Chinner <dchinner@redhat.com> > > If a filesystem writes more than one page in ->writepage, write_cache_pages > fails to notice this and continues to attempt writeback when wbc->nr_to_write > has gone negative - this trace was captured from XFS: > > > wbc_writeback_start: towrt=1024 > wbc_writepage: towrt=1024 > wbc_writepage: towrt=0 > wbc_writepage: towrt=-1 > wbc_writepage: towrt=-5 > wbc_writepage: towrt=-21 > wbc_writepage: towrt=-85 > > This has adverse effects on filesystem writeback behaviour. write_cache_pages() > needs to terminate after a certain number of pages are written, not after a > certain number of calls to ->writepage are made. This is a regression > introduced by 17bc6c30cf6bfffd816bdc53682dd46fc34a2cf4 ("vfs: Add > no_nrwrite_index_update writeback control flag"), but cannot be reverted > directly due to subsequent bug fixes that have gone in on top of it.
Might be needed in -stable. Unfortunately the most important piece of information which is needed to make that decision was cunningly hidden from us behind the vague-to-the-point-of-uselessness term "adverse effects".
_what_ "adverse effects"??
| |