On Thu, Jan 13, 2011 at 15:30, Tejun Heo <tj@xxxxxxxxxx> wrote: > On Thu, Jan 13, 2011 at 3:25 PM, Milan Broz <mbroz@xxxxxxxxxx> wrote: >> Maybe, but this was not invented in DM/MD camp:-) >> Probably Kay or Greg can answer why it was done this way? It's not from Greg or Kay. It just appeared some day in the context of dm. :) And yes, symlinks *look* nice and simple for the outside, but they are not, and have all sorts of problems like non-atomic updates, make it impossible to ever rename a device (as long as they copy the device name), and and and .... we should not add more of this. >> If btrfs internally creates some virtual _block_ device for its pool, it should >> present it here too with slaves/holders. If not, why it should create any links there? > > Yeah, that's the most bothering part for me. ÂThe biggest customers of > bd_claim are filesystems and all these custom symlinkeries don't do > nothing for them. ÂIt just doesn't make a whole lot of sense to me. Btrfs does not use any blockdev as the master for good reason, and it can never map its slaves inside of /sys/block. Simple meta-blockdevs like md/dm just don't fit into modern requirements of a filesystem (directory snapshots, directory subvolumes, complex raids, hassle-free resizing, ...) -- hence btrfs is much more like a network-filesystem mount than a stream of blocks like a disk, and does not fit at all into this model. Kay -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
