On Thu, Feb 07, 2013 at 01:40:14AM -0800, Joel Becker wrote: > On Wed, Feb 06, 2013 at 03:34:49PM -0500, Chuck Lever wrote: > > > > On Feb 6, 2013, at 3:24 PM, "Darrick J. Wong" <darrick.w...@oracle.com> > > wrote: > > > > > On Wed, Feb 06, 2013 at 01:51:22PM -0600, Ben Myers wrote: > > >> Hi, > > >> > > >> I'm interested in discussing how to pass protection information to and > > >> from > > >> userspace. Maybe Martin could be enlisted for the discussion. > > >> > > >> I read that some work has already been done in this area but have not > > >> been able > > >> to locate it. It looks like the bio-integrity code already makes it > > >> possible > > >> to generate the t10-dif crc in the filesystem. It would be good to be > > >> able to > > >> get the guard and application tags back out to backup applications such > > >> as > > >> xfsdump. Enabling other applications to generate their own tags in > > >> userspace > > >> is also interesting. > > > > > > This one's been on my list for a couple of years (and companies) too. A > > > few > > > years ago Joel Becker had support for it in his sys_dio proposal (that > > > hasn't > > > gone anywhere), and more recently I've theorized that we could add a magic > > > fcntl/ioctl to make the kernel recognize, say, the first iovec of a > > > O_DIRECT > > > *{read,write}v call as the PI buffer, which I think is similar to how DIX > > > gets > > > PI data to a disk. But it's not like I have any code to show for it. > > > > > > I /think/ it's fairly straightforward to change the directio submit code > > > to > > > find the userspace PI buffer and amend the block integrity code to attach > > > our > > > own PI buffer. You'd still have to let the block layer set the sector # > > > field, > > > but afaik that won't affect the crc or the app tag. > > > > > > I hear that the NFS guys want to propose some sort of protocol for > > > transmitting > > > PI data (across NFS), but I haven't seen anything concrete yet. > > > > I'm writing a requirements document for the NFS protocol which I can > > discuss at LSF. The use cases for NFS for now would be virtual disk > > devices (hypervisors) or direct NFS access to storage from user space. > > > > Like everyone else we are waiting for a magical VFS and user space API to > > appear that can pass PI to and from storage. > > I'm happy to chat about it. Unfortunately, like Darrick says, sys_dio() > coding hasn't happened. I do think we're better off with some kind of > explicit API than some magic state on the file. I mean, even something > like: > > ssize_t write_with_pi(int fd, const void *buf, size_t count, > const void *pi, size_t pi_count); > > It's not as nice as a non-historical API (eg sys_dio), but it also > probably plays nicer with buffered I/O.
I also pondered simply adding a new io_prep_* function + IO_CMD_ code to libaio and all the other plumbing necessary to make that happen... void io_prep_preadv_pi(struct iocb *iocb, int fd, const struct iovec *iov, int iovcnt, long long offset, const void *pi, size_t pi_count); --D > > Joel > > > > > > Well, I hope I'll scrape together the time to hack together a PoC before > > > LSF... > > > on the other hand, I ran the discussion about PI userland interfaces at > > > LPC2011 > > > and (shamefully) haven't done anything yet. > > > > > > <end rambling> > > > > > > --D > > >> > > >> Regards, > > >> Ben > > >> -- > > >> To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" > > >> in > > >> the body of a message to majord...@vger.kernel.org > > >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > > -- > > > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" > > > in > > > the body of a message to majord...@vger.kernel.org > > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > -- > > Chuck Lever > > chuck[dot]lever[at]oracle[dot]com > > > > > > > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > > the body of a message to majord...@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- > > "I think it would be a good idea." > - Mahatma Ghandi, when asked what he thought of Western > civilization > > http://www.jlbec.org/ > jl...@evilplan.org -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html