Messages in this thread | | | Date | Tue, 8 Jun 2010 15:43:30 +1000 | From | Nick Piggin <> | Subject | Re: [PATCH 4/6] writeback: pay attention to wbc->nr_to_write in write_cache_pages |
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On Tue, Jun 08, 2010 at 10:38:05AM +1000, Dave Chinner 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. > > Signed-off-by: Dave Chinner <dchinner@redhat.com> > Reviewed-by: Christoph Hellwig <hch@lst.de> Acked-by: Nick Piggin <npiggin@suse.de>
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