Hi, On Wed, 2011-09-07 at 18:46 +0200, Christoph Hellwig wrote: > On Wed, Sep 07, 2011 at 06:42:16PM +0200, Jan Kara wrote: > > Well, it depends on what you call common - usually, ->writepage is called > > from kswapd which shouldn't be common compared to writeback from a flusher > > thread. But now I've realized that JBD2 also calls ->writepage to fulfill > > data=ordered mode guarantees and that's what causes most of redirtying of > > pages on ext4. That's going away eventually but it will take some time. So > > for now writeback has to handle redirtying... > > Under the "right" loads it may also happen for xfs because we can't > take lock non-blockingly in the fluser thread for example. > GFS2 uses this trick for journaled data pages - the lock ordering is transaction lock before page lock, so we cannot handle pages which are already locked before they are handed to the fs if a transaction is required. So we have our own ->writepages which gets the locks in the correct order, and ->writepage will simply redirty the page if it would have required a transaction in order to write out the page, Steve. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>