Hi, Goffredo, On Thu, Nov 04, 2010 at 11:55:24PM +0100, Goffredo Baroncelli wrote: > I make a prototype for exporting info from btrfs via sysfs.
Good stuff. I was going to take a look at doing that this weekend. :) > Under /sys/btrfs were created two directories, named "fs" and "devices". > > /sys/btrfs/fs/<fs-uuid>/ I'm pretty sure that /sys/btrfs won't get through any discussion on LKML. I'd suggest /sys/fs/btrfs as the base, since that's where the other filesystems seem to put their sysfs information. > label -> filesystem label > num_devices -> total number of devices > open_devices -> number of opened devices > [...] > /sys/btrfs/devices/<dev-uuid>/ > devid -> btrfs device number > fsid -> filesystem uuid (fs-uuid) > major, minor -> major minor I think the major, minor should instead be be a symlink to the relevant entry in /sys/devices/... (as done in /sys/block/*) or /sys/block (as done in /sys/block/md*/slaves). Call it "device". > name -> device name Unnecessary -- and also, I think, unlikely to get through LKML review. Putting a device name here implies that the kernel knows better than userspace what the name of the device is (i.e. which device node you should be using). Having the link to /sys/block/* or /sys/devices/... as above is, I think, all that's needed here. Userspace should be able to convert the major/minor pair kept in /sys/fs/btrfs/devices/<uuid>/device/dev appropriately. > writeable -> is the device writeable > where <fs-uuid> is the filesystem uuid, and <dev-uuid> is the device uuid. > The > link between devices and filesystem is the <fsid> parameter of a device. Could that be made a symlink instead? That seems to be the usual approach in sysfs. > I create these structure because we should handle the case were the devices > are present (like after a "btrfs device scan") but the filesystem aren't > mounted. ... ah, I see it can't. (Re: my previous comment) > In this case the devices/ subdirectory is populated. Instead the fs/ > subdirectory is empty. > > I don't attach a patch because the code is very ugly. > Comments ? Thoughts ? Is it ugly because there are significant difficulties in making btrfs or sysfs do this, or just because you hacked something together as quickly as possible for a demo? Hugo. -- === Hugo Mills: h...@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 515C238D from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- "There's a Martian war machine outside -- they want to talk --- to you about a cure for the common cold."
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