On Thu, 24 May 2007 23:34:33 +0100 David Howells <[EMAIL PROTECTED]> wrote:
> Andrew Morton <[EMAIL PROTECTED]> wrote: > > > So my reason for asking the above is to try to find a way to make all these > > new PG-error games just go away. > > Yeah. However, there needs to be something to cover the gap between releasing > PG_writeback and getting PG_lock. They have to be done in that order to avoid > deadlocking against truncate and other stuff, but that leaves a window in > which > the page appears to be in a good state - one in which prepare_write() or > page_mkwrite() can potentially leak through. hm. I don't see why that race window would be a problem in practice: the page-exciser does a lock_page();wait_on_page_writeback() as normal, then proceeds with its business? But given that this doesn't work right for some reason, can we use PG_error and then handle that appropriately in the filesystem's ->prepare_write() and ->page_mkwrite()? > Nick Piggin talked about using an extra lock, but as far as I can tell, that > just compounds the deadlock problems. > > I suppose I could leave something in page->private that indicated that the > page was defunct, but that'd have to be done by the filesystem, probably > before calling cancel_rejected_write(). Well, using PG_error is OK and appropriate for that if it's localised to the fs. But I'd be a bit worried about requiring that the VFS maintain some special protocol for it, partly because it would be such a rarely-tested thing. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/