On Sat, 2014-12-13 at 08:33 +0100, James Bottomley wrote: > On Fri, 2014-12-12 at 17:53 -0800, Nicholas A. Bellinger wrote: > > On Sat, 2014-12-13 at 00:52 +0100, James Bottomley wrote: > > > On Fri, 2014-12-12 at 14:59 -0800, Nicholas A. Bellinger wrote: > > > > Hello T10/SCSI folks, > > > > > > > > A question came up on the LIO target-devel mailing list recently wrt the > > > > proper handling of Persistent Reservations + All Registrants logic in a > > > > couple of different scenarios. <SNIP> > > > > How about when the explicit reservation is removed..? Do the implicit > > > > reservations need to remain in effect for the existing registrations, > > > > even though the explicit reservation of All Registrants type no longer > > > > exists..? > > > > > > Again, I don't understand the distinction between implicit and explicit. > > > For an all registrants reservation, all registered initiators are the > > > reservation holder so any one of them may release the reservation. Once > > > the reservation is released, there's no reservation at all. > > > > So some initiator still needs to perform the actual RESERVE, right..? > > Yes, there's no reservation until a reserve is issued. > > > That is, a number of registrations don't become 'implicit' reservation > > holders until one initiator performs an 'explicit' RESERVE with type=All > > Registrants. > > Once one initiator issues an all registrants reservation, all registants > become the reservation holder. > > > > > The second point that Ilias raised is what should be the correct > > > > R_HOLDER bit status for PRIN READ_FULL_STATUS descriptors when All > > > > Registrants type is specified. My original interpretation was that > > > > R_HOLDER was to signal the explicit reservation holder obtained with > > > > PR-OUT RESERVE, and not for the implicit reservations from the other > > > > registrations. Is this the correct approach..? > > > > > > R_HOLDER is set for any initiator that would be defined to be the > > > persistent reservation holder in section 5.6.9 > > > > > > > Well, section 5.6.9 only mentions the use of RESERVE, so that would seem > > to indicate the original interpretation + current code for > > READ_FULL_STATUS is correct. > > It should be set for every registered initiator in the all registrants > case (because they're all the reservation holder). > Thanks for the clarification on this. > > > > Also, does anyone have any experience with a host side implementation of > > > > All Registrants to use as a reference for what's already out in the > > > > wild..? > > > > > > I know what was negotiated to support clustering (which is a pretty tiny > > > subset). However, I think your point of confusion is trying to > > > distinguish between what you call implicit and explicit reservations ... > > > there's no such thing. There's only a reservation holder which may be > > > many initiators, So it's binary: a given initiator either is or is not > > > the reservation holder. Section 5.6 needs to be read in that context. > > > > > > > The confusion is around when registrations who don't issue an explicit > > RESERVE become implicit reservation holders. Is it when one initiator > > does an explicit RESERVE + type=All Registrants, or is it when REGISTER > > + type=All Registrants occurs..? > > There is no reservation until a reserve command is issued. Once an all > registrants reservation is issued, by any registered initator, all > registered initators then become the reservation holder. > So based on the above, the issue raised by Ilias where once the original All Registrants reservation is released, the other registrations lose their 'implicit' reservation until someone does another RESERVE + type=All Registrants is a bug. Working on a proper bugfix for this now. Thanks James! --nab -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
