On Wed, Sep 07, 2011 at 02:22:22AM +0200, Jan Kara wrote: > > So wtf is ext4 doing? Shouldn't a page stay dirty until its written out? > > > > That is, should we really frob around this behaviour or fix ext4 because > > its on crack? > Fengguang, could you please verify your findings with recent kernel? I > believe ext4 got fixed in this regard some time ago already (and yes, old > delalloc writeback code in ext4 was terrible). The pattern we do in writeback is: in pageout / write_cache_pages: lock_page(); clear_page_dirty_for_io(); in ->writepage: set_page_writeback(); unlock_page(); end_page_writeback(); So whenever ->writepage decides it doesn't want to write things back we have to redirty pages. We have this happen quite a bit in every filesystem, but ext4 hits it a lot more than usual because it refuses to write out delalloc pages from plain ->writepage and only allows ->writepages to do it. -- 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>