Messages in this thread | | | Date | Mon, 23 Jan 2006 13:14:46 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH 6/9] device-mapper snapshot: barriers not supported |
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Lars Marowsky-Bree <lmb@suse.de> wrote: > > On 2006-01-22T21:41:11, Andrew Morton <akpm@osdl.org> wrote: > > > Alasdair G Kergon <agk@redhat.com> wrote: > > > > > > The snapshot and origin targets are incapable of handling barriers and > > > need to indicate this. > > > > > > ... > > > > > > + if (unlikely(bio_barrier(bio))) > > > + return -EOPNOTSUPP; > > > + > > > > And what was happening if people _were_ sending such BIOs down? Did it all > > appear to work correctly? If so, will this change cause > > currently-apparently-working setups to stop working? > > Filesystems basically disable using barriers on a device which doesn't > support them, which is indicated by -EOPNOTSUPP. Barriers are allowed to > fail in such fashion. > > Now the interesting question is what happens when barriers are suddenly > verboten on a stack which used to support them - because the new mapping > doesn't support it _anymore_. Hrm. _Should_ work, but probably not > tested much ;-) >
I don't understand that, sorry.
My concern is: has the above change any potential to cause currently-working setups to stop working?
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