On Mon, Mar 14, 2011 at 01:10:42PM -0700, Andrew Morton wrote: > > There might one day be a requirement to be able to initiate a > resource-management-style writeback against a whole filesystem. When > that happens, we'll regret not having added a "mode" argument to > sys_syncfs(). I'm a bit nervous about exposing WB_SYNC_NONE to userspace, because its semantics are *definitely* hard to describe. For example, at the moment if you do a WB_SYNC_NONE writeback, the writeback code will clamp the amount of data written back for each inode to MAX_WRITEBACK_PAGES (1024) pages. Do we want to document that? Probably not! But if we don't document it, what can userspace expect? If you just issue a writeback_inodes_sb(), it's not the case that it will start a process that will eventually write out everything (i.e., it's not the equivalent of a non-blocking data integrity sync). It just means, "write out some stuff". I could imagine userspace wanting to start a non-blocking writeout of all data blocking pages, and which doesn't cause queue flush / barrier requests. (i.e., a non-blocking-non-barrier-issuing-but-otherwise-a- data-integrity writeback) But that's not something that the current writeback machinery can do easily, at least not today. It wouldn't hurt to have a "flags" field which we could expand later --- but that can lead to portability headaches for userspace programs that don't know whether a particular kernel is going to support a particular flag or not. So it's certainly not a panacea. - Ted -- 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
