On Sun, Mar 01, 2009 at 07:17:44PM +1100, Dave Chinner wrote: > On Wed, Feb 25, 2009 at 10:36:29AM +0100, Nick Piggin wrote: > > I need this in fsblock because I am working to ensure filesystem metadata > > can be correctly allocated and refcounted. This means that page cleaning > > should not require memory allocation (to be really robust). > > Which, unfortunately, is just a dream for any filesystem that uses > delayed allocation. i.e. they have to walk the free space trees > which may need to be read from disk and therefore require memory > to succeed.... Well it's a dream because probably none of them get it right, but that doesn't mean its impossible. You don't need complete memory allocation up-front to be robust, but having reserves or degraded modes that simply guarantee forward progress is enough. For example, if you need to read/write filesystem metadata to find and allocate free space, then you really only need a page to do all the IO. -- 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
