On Fri, Apr 1, 2011 at 2:46 PM, Joel Becker <jlbec@xxxxxxxxxxxx> wrote: > On Fri, Apr 01, 2011 at 09:30:04AM -0700, Amir Goldstein wrote: >> when writing DIO to indirect mapped file holes, we fall back to buffered write >> (so we won't expose stale data in the case of a crash) concurrent DIO reads >> to that file (before data writeback) can expose stale data. right? >> do you consider this case mixing buffered and DIO access? >> do you consider that as a problem? > > I do not consider this 'mixing', nor do I consider it a problem. > ocfs2 does exactly this for holes, unwritten extents, and CoW. It does > not violate the user's expectation that the data will be on disk when > the write(2) returns. > Falling back to buffered on read(2) is a different story; the > caller wants the current state of the disk block, not five minutes ago. > So we can't do that. But we also don't need to. the issue is with DIO read exposing uninitialized data on disk is a security issue. it's not about giving the read what is expects to see. > O_DIRECT users that are worried about any possible space usage in > the page cache have already pre-allocated their disk blocks and don't > get here. > > Joel > > -- > > "Under capitalism, man exploits man. Under Communism, it's just > the opposite." > - John Kenneth Galbraith > > http://www.jlbec.org/ > jlbec@xxxxxxxxxxxx > -- 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
