I see this is a completely unsupported feature I use now. Can anyone explain will volume-del also work on a non-empty volume if I have enough space on my HAMMER file system to move data to? For example, will the following scenario work, if I add a new 1TB volume and delete an old one of 500GB?
2015-08-31 22:10 GMT+03:00 Tomohiro Kusumi <kusumi.tomoh...@gmail.com>: > There is a critical kernel panic issue while running hammer volume-del. > I've seen this happens not only on master, but also 4.2.4 release kernel > (which was before I started to touch hammer volume-add|del ioctl code) and > probably older kernels too from the way it works. > > This seems to be a timing issue, race between ioctl called by a volume-del > process and the flusher kernel thread. It's relatively easy to reproduce in > my environment with >=4 volumes but never with 2 or 3 volumes. The first > one or two volumes need to be filled up and make reblock run before > unloading the volume in order to reproduce this. > > In the worst case, a volume gets removed and volume header gets erased as > usual, but kernel could panic before volume count of remaining volumes get > updated (decremented). This results in inconsistency between volume count > and # of valid volumes, and the filesystem will no longer be mountable > unless directly edit the volume header of block devices. > > I haven't fixed this yet, nor is it obvious, but it seems the flusher > kernel thread needs to be aware of ongoing volume-del by checking if > hmp->volume_to_remove != -1 > similar to the way blockmap allocator checks it while looking for free > space within a bigblock. >
