On Tue, 10 Feb 2026 06:44:57 +0000 Smita Koralahalli <[email protected]> wrote:
> Introduce a global "DAX Regions" resource root and register each > dax_region->res under it via request_resource(). Release the resource on > dax_region teardown. > > By enforcing a single global namespace for dax_region allocations, this > ensures only one of dax_hmem or dax_cxl can successfully register a > dax_region for a given range. > > Co-developed-by: Dan Williams <[email protected]> > Signed-off-by: Dan Williams <[email protected]> > Signed-off-by: Smita Koralahalli <[email protected]> One question inline about the locking. Is intent to serialize beyond this new resource tree? If it's just the resource tree the write_lock(&resource_lock); in the request and release_resource() should be sufficient. > --- > drivers/dax/bus.c | 23 ++++++++++++++++++++--- > 1 file changed, 20 insertions(+), 3 deletions(-) > > diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c > index fde29e0ad68b..5f387feb95f0 100644 > --- a/drivers/dax/bus.c > +++ b/drivers/dax/bus.c > @@ -10,6 +10,7 @@ > #include "dax-private.h" > #include "bus.h" > > +static struct resource dax_regions = DEFINE_RES_MEM_NAMED(0, -1, "DAX > Regions"); > static DEFINE_MUTEX(dax_bus_lock); > > /* > @@ -625,6 +626,8 @@ static void dax_region_unregister(void *region) > { > struct dax_region *dax_region = region; > > + scoped_guard(rwsem_write, &dax_region_rwsem) > + release_resource(&dax_region->res); Do we need the locking? resource stuff all runs under the global resource_lock so if aim is just to serialize adds and removes that should be enough. Maybe there is a justification in that being an internal implementation detail. > sysfs_remove_groups(&dax_region->dev->kobj, > dax_region_attribute_groups); > dax_region_put(dax_region); > @@ -635,6 +638,7 @@ struct dax_region *alloc_dax_region(struct device > *parent, int region_id, > unsigned long flags) > { > struct dax_region *dax_region; > + int rc; > > /* > * The DAX core assumes that it can store its private data in > @@ -667,14 +671,27 @@ struct dax_region *alloc_dax_region(struct device > *parent, int region_id, > .flags = IORESOURCE_MEM | flags, > }; > > - if (sysfs_create_groups(&parent->kobj, dax_region_attribute_groups)) { > - kfree(dax_region); > - return NULL; > + scoped_guard(rwsem_write, &dax_region_rwsem) > + rc = request_resource(&dax_regions, &dax_region->res); > + if (rc) { > + dev_dbg(parent, "dax_region resource conflict for %pR\n", > + &dax_region->res); > + goto err_res; > } > > + if (sysfs_create_groups(&parent->kobj, dax_region_attribute_groups)) > + goto err_sysfs; > + > if (devm_add_action_or_reset(parent, dax_region_unregister, dax_region)) > return NULL; > return dax_region; > + > +err_sysfs: > + scoped_guard(rwsem_write, &dax_region_rwsem) > + release_resource(&dax_region->res); > +err_res: > + kfree(dax_region); > + return NULL; > } > EXPORT_SYMBOL_GPL(alloc_dax_region); >
