| Message ID | 20241008145503.987195-2-m@bjorling.me (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | nvme: add rotational support | expand |
On 10/8/24 16:55, Matias Bjørling wrote: > From: Matias Bjørling <matias.bjorling@wdc.com> > > The NVMe 2.0 specification adds an independent identify namespace > data structure that contains generic attributes that apply to all > namespace types. Some attributes carry over from the NVM command set > identify namespace data structure, and others are new. > > Currently, the data structure only considered when CRIMS is enabled or > when the namespace type is key-value. > > However, the independent namespace data structure > is mandatory for devices that implement features from the 2.0+ > specification. Therefore, we can check this data structure first. If > unavailable, retrieve the generic attributes from the NVM command set > identify namespace data structure. > > Signed-off-by: Matias Bjørling <matias.bjorling@wdc.com> > --- > drivers/nvme/host/core.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c > index 0dc8bcc664f2..9cbef6342c39 100644 > --- a/drivers/nvme/host/core.c > +++ b/drivers/nvme/host/core.c > @@ -3999,7 +3999,7 @@ static void nvme_scan_ns(struct nvme_ctrl *ctrl, unsigned nsid) > { > struct nvme_ns_info info = { .nsid = nsid }; > struct nvme_ns *ns; > - int ret; > + int ret = 1; > > if (nvme_identify_ns_descs(ctrl, &info)) > return; > @@ -4015,10 +4015,9 @@ static void nvme_scan_ns(struct nvme_ctrl *ctrl, unsigned nsid) > * data structure to find all the generic information that is needed to > * set up a namespace. If not fall back to the legacy version. > */ > - if ((ctrl->cap & NVME_CAP_CRMS_CRIMS) || > - (info.ids.csi != NVME_CSI_NVM && info.ids.csi != NVME_CSI_ZNS)) > + if (!nvme_ctrl_limited_cns(ctrl)) > ret = nvme_ns_info_from_id_cs_indep(ctrl, &info); > - else > + if (ret > 0) > ret = nvme_ns_info_from_identify(ctrl, &info); > > if (info.is_removed) That is a very odd coding. 'info' will only be filled out for a non-zero return value of nvme_ns_info_from_cs_indep(). So why not check for that? But if we get an NVME status back there is a fair chance that something else than 'invalid field' (or whatever indicated that the command is not supported). That then would cause the device to be misdetected without the admin knowning. Shouldn't we add a message if we fall back to nvme_ns_info_from_identify()? Cheers, Hannes
On Tue, Oct 08, 2024 at 04:55:02PM +0200, Matias Bjørling wrote: > However, the independent namespace data structure > is mandatory for devices that implement features from the 2.0+ > specification. Therefore, we can check this data structure first. If > unavailable, retrieve the generic attributes from the NVM command set > identify namespace data structure. I'm not a huge fan of this. For pre-2.0 controllers this means we'll now send a command that will fail most of them time. And for all the cheap low-end consumer device I'm actually worried that they'll get it wrong and break something.
On 09-10-2024 09:46, Christoph Hellwig wrote: > On Tue, Oct 08, 2024 at 04:55:02PM +0200, Matias Bjørling wrote: >> However, the independent namespace data structure >> is mandatory for devices that implement features from the 2.0+ >> specification. Therefore, we can check this data structure first. If >> unavailable, retrieve the generic attributes from the NVM command set >> identify namespace data structure. > > I'm not a huge fan of this. For pre-2.0 controllers this means > we'll now send a command that will fail most of them time. And for > all the cheap low-end consumer device I'm actually worried that they'll > get it wrong and break something. > It's a good point. Damien, Keith, and I were debating it during ALPSS. They preferred the "send command and see if it fails" approach over writing specific conditions where it would apply. Note that Keith did suggest to avoid the command on 1.0 and 1.1 devices, and they were known to fail with unsupported CNS ids. If making the check conditional, I think checking if the device follows 2.0 specification isn't sufficient, as some devices may implement a subset of the 2.0 features (for example the independent ns data struct), while reporting as a 1.4 device. Is there maybe better way, that isn't dependent on some feature being implemented (such as CRIMS capability)?
On 09-10-2024 08:16, Hannes Reinecke wrote: > On 10/8/24 16:55, Matias Bjørling wrote: >> From: Matias Bjørling <matias.bjorling@wdc.com> >> >> The NVMe 2.0 specification adds an independent identify namespace >> data structure that contains generic attributes that apply to all >> namespace types. Some attributes carry over from the NVM command set >> identify namespace data structure, and others are new. >> >> Currently, the data structure only considered when CRIMS is enabled or >> when the namespace type is key-value. >> >> However, the independent namespace data structure >> is mandatory for devices that implement features from the 2.0+ >> specification. Therefore, we can check this data structure first. If >> unavailable, retrieve the generic attributes from the NVM command set >> identify namespace data structure. >> >> Signed-off-by: Matias Bjørling <matias.bjorling@wdc.com> >> --- >> drivers/nvme/host/core.c | 7 +++---- >> 1 file changed, 3 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c >> index 0dc8bcc664f2..9cbef6342c39 100644 >> --- a/drivers/nvme/host/core.c >> +++ b/drivers/nvme/host/core.c >> @@ -3999,7 +3999,7 @@ static void nvme_scan_ns(struct nvme_ctrl *ctrl, >> unsigned nsid) >> { >> struct nvme_ns_info info = { .nsid = nsid }; >> struct nvme_ns *ns; >> - int ret; >> + int ret = 1; >> if (nvme_identify_ns_descs(ctrl, &info)) >> return; >> @@ -4015,10 +4015,9 @@ static void nvme_scan_ns(struct nvme_ctrl >> *ctrl, unsigned nsid) >> * data structure to find all the generic information that is >> needed to >> * set up a namespace. If not fall back to the legacy version. >> */ >> - if ((ctrl->cap & NVME_CAP_CRMS_CRIMS) || >> - (info.ids.csi != NVME_CSI_NVM && info.ids.csi != NVME_CSI_ZNS)) >> + if (!nvme_ctrl_limited_cns(ctrl)) >> ret = nvme_ns_info_from_id_cs_indep(ctrl, &info); >> - else >> + if (ret > 0) >> ret = nvme_ns_info_from_identify(ctrl, &info); >> if (info.is_removed) > > That is a very odd coding. 'info' will only be filled out for a non-zero > return value of nvme_ns_info_from_cs_indep(). I may have misunderstood. Only if nvme_ns_info_from_cs_indep() return 0 will the information be filled. Otherwise, if it is an NVMe error, nvme_ns_info_from_identify() is tried, otherwise it's a hard error, and it errors out completely. > So why not check for that? > But if we get an NVME status back there is a fair chance that something > else than 'invalid field' (or whatever indicated that the command is not > supported). That then would cause the device to be misdetected without > the admin knowning. > Shouldn't we add a message if we fall back to nvme_ns_info_from_identify()? Hmm, we could. Buuuut, at this point, there's more devices falling back to nvme_ns_info_from_identify(), than devices that implements the independent ns identify data structure. So I wouldn't mind it being silent. If we want to debug a potential misdetection, tracing could be enabled to track down what's happening. > > Cheers, > > Hannes
On Wed, Oct 09, 2024 at 09:46:11AM +0200, Christoph Hellwig wrote: > On Tue, Oct 08, 2024 at 04:55:02PM +0200, Matias Bjørling wrote: > > However, the independent namespace data structure > > is mandatory for devices that implement features from the 2.0+ > > specification. Therefore, we can check this data structure first. If > > unavailable, retrieve the generic attributes from the NVM command set > > identify namespace data structure. > > I'm not a huge fan of this. For pre-2.0 controllers this means > we'll now send a command that will fail most of them time. And for > all the cheap low-end consumer device I'm actually worried that they'll > get it wrong and break something. We already send identify commands that we expect may break on pre-2.0 controllers: the Identify NS Descriptor List. We have other quirks for disabling specific identifications (ex: nvme_ctrl_limited_cns, NVME_QUIRK_NO_NS_DESC_LIST) in case something really break certain identifies. But I think anything >= 1.3 should be fine: the CNS handling is well defined from that point onward, so we shouldn't make anything harder than necessary from assuming someone got identication this wrong. The only pain I can think of is that some controllers increment their error log count, and SMART tools creates unnecessary alerts for that.
On Wed, Oct 09, 2024 at 08:56:32AM -0600, Keith Busch wrote: > On Wed, Oct 09, 2024 at 09:46:11AM +0200, Christoph Hellwig wrote: > > On Tue, Oct 08, 2024 at 04:55:02PM +0200, Matias Bjørling wrote: > > > However, the independent namespace data structure > > > is mandatory for devices that implement features from the 2.0+ > > > specification. Therefore, we can check this data structure first. If > > > unavailable, retrieve the generic attributes from the NVM command set > > > identify namespace data structure. > > > > I'm not a huge fan of this. For pre-2.0 controllers this means > > we'll now send a command that will fail most of them time. And for > > all the cheap low-end consumer device I'm actually worried that they'll > > get it wrong and break something. > > We already send identify commands that we expect may break on pre-2.0 > controllers: the Identify NS Descriptor List. Identify NS Descriptor List is mandatory starting with NVMe 1.3. We only issue it for 1.3 or if the controller advertises supporting multiple command sets.
On Wed, Oct 09, 2024 at 03:19:59PM GMT, Matias Bjørling wrote: > On 09-10-2024 09:46, Christoph Hellwig wrote: > > On Tue, Oct 08, 2024 at 04:55:02PM +0200, Matias Bjørling wrote: > > > However, the independent namespace data structure > > > is mandatory for devices that implement features from the 2.0+ > > > specification. Therefore, we can check this data structure first. If > > > unavailable, retrieve the generic attributes from the NVM command set > > > identify namespace data structure. > > > > I'm not a huge fan of this. For pre-2.0 controllers this means > > we'll now send a command that will fail most of them time. And for > > all the cheap low-end consumer device I'm actually worried that they'll > > get it wrong and break something. > > > > It's a good point. Damien, Keith, and I were debating it during ALPSS. They > preferred the "send command and see if it fails" approach over writing > specific conditions where it would apply. Note that Keith did suggest to > avoid the command on 1.0 and 1.1 devices, and they were known to fail with > unsupported CNS ids. FWIW, there are some devices out there which will log these attempts and spam their error logs. There were plenty of reports against nvme-cli when nvme-cli issued a command which could fail.
On 10-10-2024 16:47, Daniel Wagner wrote: > On Wed, Oct 09, 2024 at 03:19:59PM GMT, Matias Bjørling wrote: >> On 09-10-2024 09:46, Christoph Hellwig wrote: >>> On Tue, Oct 08, 2024 at 04:55:02PM +0200, Matias Bjørling wrote: >>>> However, the independent namespace data structure >>>> is mandatory for devices that implement features from the 2.0+ >>>> specification. Therefore, we can check this data structure first. If >>>> unavailable, retrieve the generic attributes from the NVM command set >>>> identify namespace data structure. >>> >>> I'm not a huge fan of this. For pre-2.0 controllers this means >>> we'll now send a command that will fail most of them time. And for >>> all the cheap low-end consumer device I'm actually worried that they'll >>> get it wrong and break something. >>> >> >> It's a good point. Damien, Keith, and I were debating it during ALPSS. They >> preferred the "send command and see if it fails" approach over writing >> specific conditions where it would apply. Note that Keith did suggest to >> avoid the command on 1.0 and 1.1 devices, and they were known to fail with >> unsupported CNS ids. > > FWIW, there are some devices out there which will log these attempts and > spam their error logs. There were plenty of reports against nvme-cli > when nvme-cli issued a command which could fail. Got it. So, given the feedback from you, Keith, and Christoph. It's safe to say it needs to be a conditional check. Would anyone object if the if ((ctrl->cap & NVME_CAP_CRMS_CRIMS) || (info.ids.csi != NVME_CSI_NVM && info.ids.csi != NVME_CSI_ZNS)) statement would include a check for endurance group support? The idea being that it's mandatory for a device to implement an endurance group in case it exposes the rotational flag. That check would limit the failed command check to relatively new devices.
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c index 0dc8bcc664f2..9cbef6342c39 100644 --- a/drivers/nvme/host/core.c +++ b/drivers/nvme/host/core.c @@ -3999,7 +3999,7 @@ static void nvme_scan_ns(struct nvme_ctrl *ctrl, unsigned nsid) { struct nvme_ns_info info = { .nsid = nsid }; struct nvme_ns *ns; - int ret; + int ret = 1; if (nvme_identify_ns_descs(ctrl, &info)) return; @@ -4015,10 +4015,9 @@ static void nvme_scan_ns(struct nvme_ctrl *ctrl, unsigned nsid) * data structure to find all the generic information that is needed to * set up a namespace. If not fall back to the legacy version. */ - if ((ctrl->cap & NVME_CAP_CRMS_CRIMS) || - (info.ids.csi != NVME_CSI_NVM && info.ids.csi != NVME_CSI_ZNS)) + if (!nvme_ctrl_limited_cns(ctrl)) ret = nvme_ns_info_from_id_cs_indep(ctrl, &info); - else + if (ret > 0) ret = nvme_ns_info_from_identify(ctrl, &info); if (info.is_removed)