[PATCH 1/1] nvme : Add ioctl to query nvme attributes

[Joel Granados]

On Thu, Nov 03, 2022 at 04:56:21PM +0000, Chaitanya Kulkarni wrote:
> On 11/3/22 05:27, Joel Granados wrote:
> > An ioctl (NVME_IOCTL_GET_ATTR) is added to query nvme controller
> > attributes needed to effectively write to the char device without needing
> > to be a privileged user.  They are also provided on block devices for
> > convenience. The attributes here are meant to complement what you can
> > already get with the allowed identify commands.
> > 
> > New members are added to the nvme_ctrl struct: dmsl, vsl and wusl from
> > the I/O Command Set Specific Identify Controller Data Structure in the nvme
> > spec.
> > 
> > We add NVME_IOCTL_GET_ATTR_{V0SZ,CURZS} in order to make the ioctl
> > extensible. These serve as both size and version. The caller is expected to
> > pass the structure size as the first member of the struct. For example:
> > 
> > 	{...
> > 	struct nvme_get_attr nvme_get_attr = {0};
> > 	nvme_get_attr.argsz = sizeof(struct nvme_get_attr);
> > 	...}
> > 
> > Signed-off-by: Joel Granados <j.granados at samsung.com>
> > ---
> >   drivers/nvme/host/core.c        |  5 ++-
> >   drivers/nvme/host/ioctl.c       | 57 +++++++++++++++++++++++++
> >   drivers/nvme/host/nvme.h        | 11 +++++
> >   include/uapi/linux/nvme_ioctl.h | 74 +++++++++++++++++++++++++++++++++
> >   4 files changed, 146 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> > index 0090dc0b3ae6..267f28592b9d 100644
> > --- a/drivers/nvme/host/core.c
> > +++ b/drivers/nvme/host/core.c
> > @@ -3062,9 +3062,12 @@ static int nvme_init_non_mdts_limits(struct nvme_ctrl *ctrl)
> >   
> >   	if (id->dmrl)
> >   		ctrl->max_discard_segments = id->dmrl;
> > -	ctrl->dmrsl = le32_to_cpu(id->dmrsl);
> >   	if (id->wzsl)
> >   		ctrl->max_zeroes_sectors = nvme_mps_to_sectors(ctrl, id->wzsl);
> > +	ctrl->dmrsl = le32_to_cpu(id->dmrsl);
> > +	ctrl->dmsl = le64_to_cpu(id->dmsl);
> > +	ctrl->vsl = id->vsl;
> > +	ctrl->wusl = id->wusl;
> >   
> >   free_data:
> >   	kfree(id);
> > diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
> > index 9273db147872..2197a2b7ab56 100644
> > --- a/drivers/nvme/host/ioctl.c
> > +++ b/drivers/nvme/host/ioctl.c
> > @@ -53,6 +53,57 @@ static void __user *nvme_to_user_ptr(uintptr_t ptrval)
> >   	return (void __user *)ptrval;
> >   }
> >   
> > +static inline u32 nvme_sectors_to_mps(struct nvme_ctrl *ctrl, u32 unit)
> > +{
> > +	return ilog2(unit) + 9 - 12 - NVME_CAP_MPSMIN(ctrl->cap);
> > +}
> > +
> > +static int nvme_ctrl_export_attrs(struct nvme_ctrl *ctrl,
> > +				  struct nvme_get_attr __user *arg)
> > +{
> > +	struct nvme_get_attr nvme_get_attr = {0};
> > +	__u32 usize, retsize;
> > +	int ret;
> > +
> > +	BUILD_BUG_ON(sizeof(struct nvme_get_attr) < NVME_IOCTL_GET_ATTR_V0SZ);
> > +	BUILD_BUG_ON(sizeof(struct nvme_get_attr) != NVME_IOCTL_GET_ATTR_CURSZ);
> > +
> 
> Is there a common helper function where al the sizes validated ?
> if so please move it there ....
> 
> > +	if (copy_from_user(&nvme_get_attr, arg, 2 * sizeof(__u32)))
> > +		return -EFAULT;
> > +
> > +	if (nvme_get_attr.flags != 0)
> > +		return -EINVAL;
> > +
> > +	if (nvme_get_attr.argsz < NVME_IOCTL_GET_ATTR_V0SZ)
> > +		return -EINVAL;
> > +	usize = nvme_get_attr.argsz;
> > +
> > +	// Enforce backwards compatibility
> 
> /**/ style comments only ...
> 
> > +	ret = copy_struct_from_user(&nvme_get_attr, NVME_IOCTL_GET_ATTR_CURSZ, arg, usize);
> 
> overly long line ?
> 
> > +	if (ret)
> > +		return ret;
> > +
> > +	nvme_get_attr.argsz = NVME_IOCTL_GET_ATTR_CURSZ;
> > +	nvme_get_attr.mpsmin = NVME_CAP_MPSMIN(ctrl->cap);
> > +	nvme_get_attr.vsl = ctrl->vsl;
> > +	nvme_get_attr.wusl = ctrl->wusl;
> > +	nvme_get_attr.dmrl = ctrl->max_discard_segments;
> > +	nvme_get_attr.dmsl = ctrl->dmsl;
> > +	nvme_get_attr.dmrsl = ctrl->dmrsl;
> > +	nvme_get_attr.oncs = ctrl->oncs;
> > +	if (ctrl->max_zeroes_sectors > 0)
> > +		nvme_get_attr.wzsl = nvme_sectors_to_mps(ctrl, ctrl->max_zeroes_sectors);
> > +	if (ctrl->max_hw_sectors > 0)
> > +		nvme_get_attr.mdts = nvme_sectors_to_mps(ctrl, ctrl->max_hw_sectors);
> > +
> > +	retsize = min(usize, NVME_IOCTL_GET_ATTR_CURSZ);
> > +	if (copy_to_user((struct nvme_get_attr __user *)arg, &nvme_get_attr,
> > +			 retsize))
> 
> normal function style is
> 
> ret = function_call();
> if(ret)
> 	return ret;
Looking at this now and I see that we cannot follow the usual style as
copy_to_user will return the number of bytes that were not copied.
Therefore we return something more logical like -EFAULT.
I follow the pattern used in the other calls to copy_to_user in the
file.

> 
> 
> > +		return -EFAULT;
> > +
> > +	return 0;
> > +}
> > +
> 
> -ck
> 
> 
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