On Thu, Dec 11, 2008 at 02:30, Chris Mason <[EMAIL PROTECTED]> wrote: > On Tue, 2008-12-09 at 19:02 +0100, Kay Sievers wrote:
>> At a first look, it looks very promising, and I really like the idea >> that the state of the (possibly incomplete) device tree is kept in the >> kernel, and not somewhere in a file in userspace, like we usually see >> for all sorts of multi-volume/multi-device setups. It should make >> things much easier as usual. >> > > I hope so, at least its the only way I can keep my brain wrapped around > it. Yeah, it makes a lot of sense. >> Like with every other subsystem, people will expect btrfs to just work >> with hotpluggable devices, without much configuration and explicit >> setup after device connect. To assemble a mountable volume, we will >> need to find the (possibly several independent) devices containing the >> btrfs data. > > I did somewhat have hotplug in mind, there is btrfsctl -a to scan all > of /dev and btrfsctl -A to scan a single device. That works fine here. We just need to offer some non-sequential scanning for some setups, to be reliable. But that should be fine, if we find a way to plug the information together. > Now that I have something close to a stable super block location and > magic, I think the plan below is pretty good. The majority of my plan > here was to make a simple ioctl that hotplug could trigger, and let > someone who knew hotplug better make suggetions on the best way to > present the information. I have the btrfs detection code in udev since while, to be able to test it, and I'm tracking the changes. After the metadata is finalized, I will come up with a few working examples how we could make this information easily available, and possible integrate it into the tools, and we can decide what we think is the best. One thing I like to check now, if I got it correctly - the volume that gets mounted has: btrfs_super_block.fsid (the volume, may be used for mount-by-label) btrfs_super_block.label (the volume, may be used for mount-by-label) The devices the volume is assembled from, which can be several, have: btrfs_super_block.dev_item.uuid (the device uuid, not used in userspace) btrfs_super_block.dev_item.fsid (the volume uuid, matches btrfs_super_block.fsid) Is this correct? Thanks, Kay -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
