> -----Original Message----- > From: linux-raid-owner@xxxxxxxxxxxxxxx [mailto:linux-raid- > owner@xxxxxxxxxxxxxxx] On Behalf Of NeilBrown > Sent: Monday, March 14, 2011 10:54 PM > To: Kwolek, Adam > Cc: linux-raid@xxxxxxxxxxxxxxx; Williams, Dan J; Ciechanowski, Ed; > Neubauer, Wojciech > Subject: Re: [PATCH 0/3] UT and error case changes > > On Mon, 14 Mar 2011 15:09:20 +0100 Adam Kwolek <adam.kwolek@xxxxxxxxx> > wrote: > > > The following series implements 2 changes: > > 1. Fix for unit tests failure. > > UT suits 12 and 13 fails, when backup file cannot be opened > > for grow operation (backup file exists already). > > Thanks - applied. > > > > > > 2. I've got proposal for handling/rollback metadata in error case. > > Currently in case of error external metadata can remain in reshape > state. > > In some cases metadata can be automatically restored to initial state > > (i.e. metadata during imsm container operation can be rolled back > > when error occurs on first reshaped array before reshape is started). > > For such cases, additional superswitch function can be introduced. > > > > Metadata shouldn't be rolled back in restart case. > > I'm passing restart flag to abort function in Grow.c only, as this is > general rule. > > In the same way array reshape state is checked. > > > > This is proposal, so I've put no implementation in to imsm handler (no > metadata update is created yet). > > Please let me know your opinion. If you will like it, I'll fill out > gaps in imsm code. > > I'm not sure.. it sounds like it might be a good idea, but I'd like to > have > some concrete examples to help me think about it. I've got this idea during correcting UT so, i.e.: wrong/already existing/ backup file name passed by used. Backup file verification/opening is when metadata is in reshape state already. This error causes mdadm exit at reshape position == 0. It is too early position for reshape restart. User has manually restore metadata information and this can be quite difficult. Metadata rollback can be possible for container operation if: 1. external metadata case (checked in Grow.c) 2. This is action on first array in container (check in metadata handler) 2. md doesn't start reshape (checked in Grow.c) 3. Other conditions/metadata specific (checked in Grow.c) We can also pass some additional status to reshape_container() to indicate that metadata is rolled back and allow for container unfreeze in such case also. This can allow mdadm to leave array/container in state that work is started from (hopefully ;)). BR Adam > > Do you have an example in mind of an error which might be detected after > the metadata has been updated, but before the reshape has actually > started, > and for which reverting the metadata update is likely to be useful? > > The more general case of changing your mind just after a reshape has > started and asking the reshape to revert would certainly be useful, but > md isn't capable of that in general (yet). > > Thanks, > NeilBrown > > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
