On Fri, Jan 07, 2011 at 02:24:30AM -0500, Christoph Hellwig wrote: > On Fri, Jan 07, 2011 at 03:47:34PM +1100, Nick Piggin wrote: > > No, you misunderstand 1. I am saying they should be treated as > > WB_SYNC_NONE. > > > > In fact 2 would cause much more IO, because dirty writeout would > > never clean them so it will just keep writing them out. I don't > > know how 2 could be feasible. > > WB_SYNC_NONE means ->write_inode behaves non-blocking. That is > we do not block on memory allocations, and we do not take locks > blocking. Most journaling filesystems currently take the easy > way out an make it a no-op due to that, but take a look at XFS > how complicated it is to avoid the blocking if you want a non-noop > implementation. Btw, there's an easy way how we could get this right, in fact the write_inode in XFS is already trying to do it, it's just the caller not copying with it: - if we can't get locks for a non-blocking ->write_inode we return EAGAIN, and the callers sets the dirty bits again. -- 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
