On Wed, Jan 20, 2021 at 03:37:57PM +0100, Jan Beulich wrote: > On 20.01.2021 15:35, Roger Pau Monné wrote: > > On Wed, Jan 20, 2021 at 03:23:30PM +0100, Arthur Borsboom wrote: > >> Hi Roger, > >> > >> I have set up a test environment based on Linux 5.11.0-rc4. > >> The patch did not apply clean, so I copied/pasted the patch manually. > >> > >> Without the patch the call trace (as reported) is visible in dmesg. > >> With the patch the call trace in dmesg is gone, but ... (there is always a > >> but) ... > >> > >> Now the discard action returns the following. > >> > >> [arthur@test-arch ~]$ sudo fstrim -v / > >> fstrim: /: the discard operation is not supported > >> > >> It might be correct, but of course I was hoping the Xen VM guest would pass > >> on the discard request to the block device in the Xen VM host, which is a > >> disk partition. > >> Any suggestions? > > > > Hm, that's not what I did see on my testing, the operation worked OK, > > and that's what I would expect to happen in your case also, since I > > know the xenstore keys. > > Does discard work on partitions (and not just on entire disks)? > It's been a while since I last had anything to do with this code, > so I may well misremember. The command provided did work for me, ie: # fstrim -v / /: 19.8 GiB (21190717440 bytes) trimmed AFAICT the blkif discard interface we provide operates at physical block granularity, so it's possible to discard a single block, and hence should work against partitions. Roger.