On Fri, May 13, 2011 at 11:36:05AM +0800, Wu Fengguang wrote: > On Fri, May 13, 2011 at 06:44:20AM +0800, Dave Chinner wrote: > > On Thu, May 12, 2011 at 09:57:09PM +0800, Wu Fengguang wrote: > > > The flusher works on dirty inodes in batches, and may quit prematurely > > > if the batch of inodes happen to be metadata-only dirtied: in this case > > > wbc->nr_to_write won't be decreased at all, which stands for "no pages > > > written" but also mis-interpreted as "no progress". > > > > > > So introduce writeback_control.inodes_cleaned to count the inodes get > > > cleaned. A non-zero value means there are some progress on writeback, > > > in which case more writeback can be tried. > > > > Why introduce a new field for this? > > Yeah sorry, but this is an intermediate field that will be removed in > patch 14. > > > Just decrement nr_to_write for every write_inode() call made in > > writeback_single_inode().... > > There are two problems > > - nr_to_write has always been "# of pages written" and writeback_sb_inodes() > is actually making use of it to do page accounting in work->nr_pages. Do we really care whether it's inodes or pages that are written? As far as i can tell it doesn't, because writing inodes generally requires more IO and so needs to be limited anyway. You are already changing the definition of wbc->nr_to_write is per writeback_single_inode() call anyway, so changing it to account for indoe writeback as well is mostly irrelevant to the accounting. > - write_inode() does not always succeed, and its return value is not > reliable on every filesystem.. (I actually tried this approach in v1 > and found sync(1) hang on NFS) So put the accounting in the post-write code in writeback_single_inode() where we already check if the inode is still dirty or not. Splitting per-inode post-write processing between writeback_single_inode and the higher level code is cludgy - I'd much prefer it done in only one place. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
