On Mon, Mar 4, 2019 at 12:44 PM Javier González <javier@xxxxxxxxxxx> wrote: > > > > > On 4 Mar 2019, at 12.30, Hans Holmberg <hans@xxxxxxxxxxxxx> wrote: > > > > On Mon, Mar 4, 2019 at 10:05 AM Javier González <javier@xxxxxxxxxxx> wrote: > >>> On 27 Feb 2019, at 18.14, Igor Konopko <igor.j.konopko@xxxxxxxxx> wrote: > >>> > >>> Current lightnvm and pblk implementation does not care > >>> about NVMe max data transfer size, which can be smaller > >>> than 64*K=256K. This patch fixes issues related to that. > > > > Could you describe *what* issues you are fixing? > > > >>> Signed-off-by: Igor Konopko <igor.j.konopko@xxxxxxxxx> > >>> --- > >>> drivers/lightnvm/core.c | 9 +++++++-- > >>> drivers/nvme/host/lightnvm.c | 1 + > >>> include/linux/lightnvm.h | 1 + > >>> 3 files changed, 9 insertions(+), 2 deletions(-) > >>> > >>> diff --git a/drivers/lightnvm/core.c b/drivers/lightnvm/core.c > >>> index 5f82036fe322..c01f83b8fbaf 100644 > >>> --- a/drivers/lightnvm/core.c > >>> +++ b/drivers/lightnvm/core.c > >>> @@ -325,6 +325,7 @@ static int nvm_create_tgt(struct nvm_dev *dev, struct nvm_ioctl_create *create) > >>> struct nvm_target *t; > >>> struct nvm_tgt_dev *tgt_dev; > >>> void *targetdata; > >>> + unsigned int mdts; > >>> int ret; > >>> > >>> switch (create->conf.type) { > >>> @@ -412,8 +413,12 @@ static int nvm_create_tgt(struct nvm_dev *dev, struct nvm_ioctl_create *create) > >>> tdisk->private_data = targetdata; > >>> tqueue->queuedata = targetdata; > >>> > >>> - blk_queue_max_hw_sectors(tqueue, > >>> - (dev->geo.csecs >> 9) * NVM_MAX_VLBA); > >>> + mdts = (dev->geo.csecs >> 9) * NVM_MAX_VLBA; > >>> + if (dev->geo.mdts) { > >>> + mdts = min_t(u32, dev->geo.mdts, > >>> + (dev->geo.csecs >> 9) * NVM_MAX_VLBA); > >>> + } > >>> + blk_queue_max_hw_sectors(tqueue, mdts); > >>> > >>> set_capacity(tdisk, tt->capacity(targetdata)); > >>> add_disk(tdisk); > >>> diff --git a/drivers/nvme/host/lightnvm.c b/drivers/nvme/host/lightnvm.c > >>> index b759c25c89c8..b88a39a3cbd1 100644 > >>> --- a/drivers/nvme/host/lightnvm.c > >>> +++ b/drivers/nvme/host/lightnvm.c > >>> @@ -991,6 +991,7 @@ int nvme_nvm_register(struct nvme_ns *ns, char *disk_name, int node) > >>> geo->csecs = 1 << ns->lba_shift; > >>> geo->sos = ns->ms; > >>> geo->ext = ns->ext; > >>> + geo->mdts = ns->ctrl->max_hw_sectors; > >>> > >>> dev->q = q; > >>> memcpy(dev->name, disk_name, DISK_NAME_LEN); > >>> diff --git a/include/linux/lightnvm.h b/include/linux/lightnvm.h > >>> index 5d865a5d5cdc..d3b02708e5f0 100644 > >>> --- a/include/linux/lightnvm.h > >>> +++ b/include/linux/lightnvm.h > >>> @@ -358,6 +358,7 @@ struct nvm_geo { > >>> u16 csecs; /* sector size */ > >>> u16 sos; /* out-of-band area size */ > >>> bool ext; /* metadata in extended data buffer */ > >>> + u32 mdts; /* Max data transfer size*/ > >>> > >>> /* device write constrains */ > >>> u32 ws_min; /* minimum write size */ > >>> -- > >>> 2.17.1 > >> > >> I see where you are going with this and I partially agree, but none of > >> the OCSSD specs define a way to define this parameter. Thus, adding this > >> behavior taken from NVMe in Linux can break current implementations. Is > >> this a real life problem for you? Or this is just for NVMe “correctness”? > >> > >> Javier > > > > Hmm.Looking into the 2.0 spec what it says about vector reads: > > > > (figure 28):"The number of Logical Blocks (NLB): This field indicates > > the number of logical blocks to be read. This is a 0’s based value. > > Maximum of 64 LBAs is supported." > > > > You got the max limit covered, and the spec does not say anything > > about the minimum number of LBAs to support. > > > > Matias: any thoughts on this? > > > > Javier: How would this patch break current implementations? > > Say an OCSSD controller that sets mdts to a value under 64 or does not > set it at all (maybe garbage). Think you can get to one pretty quickly... So we cant make use of a perfectly good, standardized, parameter because some hypothetical non-compliant device out there might not provide a sane value? > > > > > Igor: how does this patch fix the mdts restriction? There are no > > checks on i.e. the gc read path that ensures that a lower limit than > > NVM_MAX_VLBA is enforced. > > This is the other part where the implementation breaks. No, it just does not fix it. over-and-out, Hans > > Javier