Messages in this thread | | | Date | Wed, 21 Apr 2010 00:28:19 +0100 | From | Jamie Lokier <> | Subject | Re: [PATCH 5/4] writeback: limit write_cache_pages integrity scanning to current EOF |
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Dave Chinner wrote: > sync can currently take a really long time if a concurrent writer is > extending a file. The problem is that the dirty pages on the address > space grow in the same direction as write_cache_pages scans, so if > the writer keeps ahead of writeback, the writeback will not > terminate until the writer stops adding dirty pages. > > For a data integrity sync, we only need to write the pages dirty at > the time we start the writeback, so we can stop scanning once we get > to the page that was at the end of the file at the time the scan > started. > > This will prevent operations like copying a large file preventing > sync from completing as it will not write back pages that were > dirtied after the sync was started. This does not impact the > existing integrity guarantees, as any dirty page (old or new) > within the EOF range at the start of the scan will still be > captured.
I guess it can still get stuck if someone does ftruncate() first, then writes to the hole?
-- Jamie
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