On Mon, Oct 01, 2012 at 03:23:41PM -0700, Kent Overstreet wrote: > So, I and other people keep running into things where we really need to > add an interface to pass some auxiliary... stuff along with a pread() or > pwrite(). Sure. Martin (cc:ed) will sympathize. > A few examples: > > * IO scheduler hints... > * Cache hints... > > * Passing checksums out to userspace. We've got bio integrity, which is > a (somewhat) generic interface for passing data checksums between the > filesystem and the hardware. Hmm, careful here. I think that in DIF/DIX the checksums are per-sector, not per IO, right? That'd mean that the PAGE_SIZE attr limit in this patch would be magically creating different max IO size limits on different architectures. That doesn't seem great. > Hence, AIO attributes. I have to be honest: I really don't like tying the interface to AIO, but I guess it's the only per-io facility we have today. It'd be nice to include sync O_DIRECT when designing the interface to make sure that it is possible to use generic syscalls in the future without running up against unexpected problems. > An iocb_attr has an id field, and a size field - and some amount of data > specific to that attribute. I'd hope that we can come up with a less fragile interface. The kernel would have to scan the attributes to make sure that there aren't malicious sizes. I only quickly glanced at the loops, but it seemed like you could have a 0 size attribute in there and _next() would spin forever. - z -- 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
