My quick Google says that should be enough, but I haven't done it myself...sorry. :( On Thu, Jan 30, 2014 at 7:27 AM, Jean-Tiare LE BIGOT <jean-tiare.le-bigot@xxxxxxx> wrote: > Hi Greg, > > Thanks for your answer. I did > > $ mount -t ext4 -o discard /dev/rbd1 /mnt > # did not see any DISCARD op after that > $ fstrim /mnt > # neither > > Maybe missing something there ? I expected '-o discard' to be enough ? > > > On 01/30/14 16:24, Gregory Farnum wrote: >> >> On Thu, Jan 30, 2014 at 1:31 AM, Jean-Tiare LE BIGOT >> <jean-tiare.le-bigot@xxxxxxx> wrote: >>> >>> Hi, >>> >>> I started to implement 'DISCARD' support in RBD kernel driver as >>> described >>> on http://tracker.ceph.com/issues/190 >>> >>> This first (easy) step was to add at the end of >>> drivers/block/rbd.c:rbd_init_disk >>> >>> /* Advertise discard support for aligned blocks */ >>> queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q); >>> disk->queue->limits.discard_granularity = segment_size; >>> disk->queue->limits.discard_alignment = segment_size; >>> >>> With this both 'mount -o discard' and 'fstrim' stopped to complain about >>> missing 'DISCARD' support. Good ! >>> >>> Next step was to add support on `rbd_request_fn` which I did (sort of). >>> But >>> here I'm stuck. If I understood well FS drivers uses `REQ_DISCARD` flag >>> of >>> `rq->cmd_flags` to notify the driver of the discard operation. But the >>> problem is that (rq->cmd_flags & REQ_DISCARD) never appears to be set. >>> >>> I tried copying then removing large files, lots of small files, forcing >>> fstrim. But I never got it. I must be missing something obvious but I >>> can't >>> manage to find what ? Do you have any clue what could be wrong ? >> >> >> I don't know anything about the relevant kernel internal interfaces >> here, but don't most FSes need to be told explicitly to do trimming? >> Did you do that? >> -Greg >> Software Engineer #42 @ http://inktank.com | http://ceph.com >> > > -- > Jean-Tiare, shared-hosting team > > -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
