Hi Chris, On 12/05/2014 07:43 PM, Chris Mason wrote: > > > On Fri, Dec 5, 2014 at 1:15 PM, Goffredo Baroncelli > <kreij...@inwind.it> wrote: >> On 12/05/2014 05:41 PM, David Sterba wrote: >>> We're looking for good reasons to justify the existence of the >>> helper, but this is still not enough IMHO. I can see the >>> convenience to do it automatically, but this assumes no udev >>> available which is probably rare these days. >> >> I have the following reasons to support a mount.btrfs helper:
>> 1) it >> is in a good point to check that everything is ok (see the thread >> related LVM snapshot, due to a dev.uuid conflicts), >> 2) it is in a >> good point to issue a good error explanation (missing device....) >> 3) it may handle case like "degraded" mode, where the filesystem is >> not fully functional but even as degraded have "some" >> functionals.. > > Ok, these three things are worth improving, but I'd like to take a > slightly different direction. Instead of recreating chunks of btrfs > dev scan, lets extend btrfs dev scan to at the very least understand > #1 and #2. As much as possible we want to be leveraging the data in > udev instead of recreating that functionality. > > #3 is a slightly different feature, but we can have an extended btrfs > dev scan or > show explain the state of the filesystem to you. This is good suggestions > From there if we really need a mount helper, it can either use a > libbtrfs to hit the scan code or be a bash script. > Thanks for trying to smooth our or wrinkles in this area. It's > definitely worth working on, I just want to make sure we recreate as > little infrastructure as possible ;) This is an RFC because I am not sure about the "right" direction. My first goal is more to start a "sane" discussion, than provide a solution. But I have to point out that "btrfs device scan" usually is started by udev, so no possibility to show [see] an error. More, btrfs dev scan is started on a device "alone", from which is impossible to check dev.uuid conflicts... [except if you accept to extend the analysis to all devices] [*] Finally, if you fear that my mount helper "recreates too much infrastructure"... this is true, but it is an implementation problem; now I am looking for a "high level" solution. Goffredo [*] BTW, give a look to "[PATCH V2][BTRFS-PROGS] Don't use LVM snapshot device", patch #5; this patch try to add a check about the dev.uuid conflicts; showing an error in this case... > > -chris > > > > -- gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it> Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
