On Fri, 16 Aug 2024 09:44:29 -0500 ira.we...@intel.com wrote: > From: Navneet Singh <navneet.si...@intel.com> > > DAX regions which map dynamic capacity partitions require that memory be > allowed to come and go. Recall sparse regions were created for this > purpose. Now that extents can be realized within DAX regions the DAX > region driver can start tracking sub-resource information. > > The tight relationship between DAX region operations and extent > operations require memory changes to be controlled synchronously with > the user of the region. Synchronize through the dax_region_rwsem and by > having the region driver drive both the region device as well as the > extent sub-devices. > > Recall requests to remove extents can happen at any time and that a host > is not obligated to release the memory until it is not being used. If > an extent is not used allow a release response. > > The DAX layer has no need for the details of the CXL memory extent > devices. Expose extents to the DAX layer as device children of the DAX > region device. A single callback from the driver aids the DAX layer to > determine if the child device is an extent. The DAX layer also > registers a devres function to automatically clean up when the device is > removed from the region. > > There is a race between extents being surfaced and the dax_cxl driver > being loaded. The driver must therefore scan for any existing extents > while still under the device lock. > > Respond to extent notifications. Manage the DAX region resource tree > based on the extents lifetime. Return the status of remove > notifications to lower layers such that it can manage the hardware > appropriately. > > Signed-off-by: Navneet Singh <navneet.si...@intel.com> > Co-developed-by: Ira Weiny <ira.we...@intel.com> > Signed-off-by: Ira Weiny <ira.we...@intel.com> A few minor comments inline.
Jonathan > > --- > Changes: > [iweiny: patch reorder] > [iweiny: move hunks from other patches to clarify code changes and > add/release flows WRT dax regions] > [iweiny: use %par] > [iweiny: clean up variable names] > [iweiny: Simplify sparse_ops] > [Fan: avoid open coding range_len()] > [djbw: s/reg_ext/region_extent] > --- > drivers/cxl/core/extent.c | 76 +++++++++++++-- > drivers/cxl/cxl.h | 6 ++ > drivers/dax/bus.c | 243 > +++++++++++++++++++++++++++++++++++++++++----- > drivers/dax/bus.h | 3 +- > drivers/dax/cxl.c | 63 +++++++++++- > drivers/dax/dax-private.h | 34 +++++++ > drivers/dax/hmem/hmem.c | 2 +- > drivers/dax/pmem.c | 2 +- > 8 files changed, 391 insertions(+), 38 deletions(-) > > diff --git a/drivers/cxl/core/extent.c b/drivers/cxl/core/extent.c > index d7d526a51e2b..103b0bec3a4a 100644 > --- a/drivers/cxl/core/extent.c > +++ b/drivers/cxl/core/extent.c > @@ -271,20 +271,67 @@ static void calc_hpa_range(struct cxl_endpoint_decoder > *cxled, > hpa_range->end = hpa_range->start + range_len(dpa_range) - 1; > } > > +static int cxlr_notify_extent(struct cxl_region *cxlr, enum dc_event event, > + struct region_extent *region_extent) > +{ > + struct cxl_dax_region *cxlr_dax; > + struct device *dev; > + int rc = 0; > + > + cxlr_dax = cxlr->cxlr_dax; > + dev = &cxlr_dax->dev; > + dev_dbg(dev, "Trying notify: type %d HPA %par\n", > + event, ®ion_extent->hpa_range); > + > + /* > + * NOTE the lack of a driver indicates a notification has failed. No > + * user space coordiantion was possible. > + */ > + device_lock(dev); I'd use guard() for this as then can just return the notify result and drop local variable rc. > + if (dev->driver) { > + struct cxl_driver *driver = to_cxl_drv(dev->driver); > + struct cxl_notify_data notify_data = (struct cxl_notify_data) { > + .event = event, > + .region_extent = region_extent, > + }; > + > + if (driver->notify) { > + dev_dbg(dev, "Notify: type %d HPA %par\n", > + event, ®ion_extent->hpa_range); > + rc = driver->notify(dev, ¬ify_data); > + } > + } > + device_unlock(dev); > + return rc; > +} > > @@ -338,8 +390,20 @@ static int cxlr_add_extent(struct cxl_dax_region > *cxlr_dax, > return rc; > } > > - /* device model handles freeing region_extent */ > - return online_region_extent(region_extent); > + rc = online_region_extent(region_extent); > + /* device model handled freeing region_extent */ > + if (rc) > + return rc; > + > + rc = cxlr_notify_extent(cxlr_dax->cxlr, DCD_ADD_CAPACITY, > region_extent); > + /* > + * The region device was breifly live but DAX layer ensures it was not briefly > + * used > + */ > + if (rc) > + region_rm_extent(region_extent); > + > + return rc; > } > diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c > index 975860371d9f..f14b0cfa7edd 100644 > --- a/drivers/dax/bus.c > +++ b/drivers/dax/bus.c > +EXPORT_SYMBOL_GPL(dax_region_add_resource); > + > +int dax_region_rm_resource(struct dax_region *dax_region, > + struct device *dev) > +{ > + struct dax_resource *dax_resource; > + > + guard(rwsem_write)(&dax_region_rwsem); > + > + dax_resource = dev_get_drvdata(dev); > + if (!dax_resource) > + return 0; > + > + if (dax_resource->use_cnt) > + return -EBUSY; > + > + /* avoid races with users trying to use the extent */ Not obvious to me from local code, why does releasing the resource here avoid a race? Perhaps the comment needs expanding. > + __dax_release_resource(dax_resource); > + return 0; > +} > +EXPORT_SYMBOL_GPL(dax_region_rm_resource); > + > +static ssize_t dev_dax_resize_sparse(struct dax_region *dax_region, > + struct dev_dax *dev_dax, > + resource_size_t to_alloc) > +{ > + struct dax_resource *dax_resource; > + resource_size_t available_size; > + struct device *extent_dev; > + ssize_t alloc; > + > + extent_dev = device_find_child(dax_region->dev, dax_region, > + find_free_extent); There is a __free for put device and it will tidy this up a tiny bit. > + if (!extent_dev) > + return 0; > + > + dax_resource = dev_get_drvdata(extent_dev); > + if (!dax_resource) > + return 0; > + > + available_size = dax_avail_size(dax_resource->res); > + to_alloc = min(available_size, to_alloc); I'd put those two inline and skip the local variables unless they have more use in later patches. alloc = __dev_dax_resize(dax_resources->res, dev_dax, min(dax_avail_size(dax_resources->res), to_alloc), dax_resource); > + alloc = __dev_dax_resize(dax_resource->res, dev_dax, to_alloc, > dax_resource); > + if (alloc > 0) > + dax_resource->use_cnt++; > + put_device(extent_dev); > + return alloc; > +} > + > @@ -1494,8 +1679,14 @@ static struct dev_dax *__devm_create_dev_dax(struct > dev_dax_data *data) > device_initialize(dev); > dev_set_name(dev, "dax%d.%d", dax_region->id, dev_dax->id); > > + if (is_sparse(dax_region) && data->size) { > + dev_err(parent, "Sparse DAX region devices are created > initially with 0 size"); must be created initially with 0 size. Otherwise this error message says that they are, so why is it an error? > + rc = -EINVAL; > + goto err_id; > + } > + > rc = alloc_dev_dax_range(&dax_region->res, dev_dax, > dax_region->res.start, > - data->size); > + data->size, NULL); > if (rc) > goto err_range; > > diff --git a/drivers/dax/cxl.c b/drivers/dax/cxl.c > index 367e86b1c22a..bf3b82b0120d 100644 > --- a/drivers/dax/cxl.c > +++ b/drivers/dax/cxl.c > @@ -5,6 +5,60 @@ ... > +static int cxl_dax_region_notify(struct device *dev, > + struct cxl_notify_data *notify_data) > +{ > + struct cxl_dax_region *cxlr_dax = to_cxl_dax_region(dev); > + struct dax_region *dax_region = dev_get_drvdata(dev); > + struct region_extent *region_extent = notify_data->region_extent; > + > + switch (notify_data->event) { > + case DCD_ADD_CAPACITY: > + return __cxl_dax_add_resource(dax_region, region_extent); > + case DCD_RELEASE_CAPACITY: > + return dax_region_rm_resource(dax_region, ®ion_extent->dev); > + case DCD_FORCED_CAPACITY_RELEASE: > + default: > + dev_err(&cxlr_dax->dev, "Unknown DC event %d\n", > + notify_data->event); > + break; Might as well return here and not below. Makes it really really obvious this is the error path and currently the only one that hits the return statement. > + } > + > + return -ENXIO; > +} > static int cxl_dax_region_probe(struct device *dev) > { > @@ -24,14 +78,16 @@ static int cxl_dax_region_probe(struct device *dev) > flags |= IORESOURCE_DAX_SPARSE_CAP; > > dax_region = alloc_dax_region(dev, cxlr->id, &cxlr_dax->hpa_range, nid, > - PMD_SIZE, flags); > + PMD_SIZE, flags, &sparse_ops); > if (!dax_region) > return -ENOMEM; > > - if (cxlr->mode == CXL_REGION_DC) > + if (cxlr->mode == CXL_REGION_DC) { > + device_for_each_child(&cxlr_dax->dev, dax_region, > + cxl_dax_add_resource); > /* Add empty seed dax device */ > dev_size = 0; > - else > + } else Coding style says that you need brackets for all branches if one needs them (as multiline). Just above: https://www.kernel.org/doc/html/v4.10/process/coding-style.html#spaces > dev_size = range_len(&cxlr_dax->hpa_range); > > data = (struct dev_dax_data) {