Jonathan Cameron wrote: > On Thu, 23 Jun 2022 21:19:37 -0700 > Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > > > The core of devm_request_free_mem_region() is a helper that searches for > > free space in iomem_resource and performs __request_region_locked() on > > the result of that search. The policy choices of the implementation > > conform to what CONFIG_DEVICE_PRIVATE users want which is memory that is > > immediately marked busy, and a preference to search for the first-fit > > free range in descending order from the top of the physical address > > space. > > > > CXL has a need for a similar allocator, but with the following tweaks: > > > > 1/ Search for free space in ascending order > > > > 2/ Search for free space relative to a given CXL window > > > > 3/ 'insert' rather than 'request' the new resource given downstream > > drivers from the CXL Region driver (like the pmem or dax drivers) are > > responsible for request_mem_region() when they activate the memory > > range. > > > > Rework __request_free_mem_region() into get_free_mem_region() which > > takes a set of GFR_* (Get Free Region) flags to control the allocation > > policy (ascending vs descending), and "busy" policy (insert_resource() > > vs request_region()). > > > > Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx> > > Link: https://lore.kernel.org/linux-cxl/20220420143406.GY2120790@xxxxxxxxxx/ > > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > > Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx> > > Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> > > A few things inline, > > Thanks, > > Jonathan > > > --- > > include/linux/ioport.h | 2 + > > kernel/resource.c | 174 ++++++++++++++++++++++++++++++++--------- > > mm/Kconfig | 5 ++ > > 3 files changed, 146 insertions(+), 35 deletions(-) > > > > diff --git a/include/linux/ioport.h b/include/linux/ioport.h > > index ec5f71f7135b..ed03518347aa 100644 > > --- a/include/linux/ioport.h > > +++ b/include/linux/ioport.h > > @@ -329,6 +329,8 @@ struct resource *devm_request_free_mem_region(struct device *dev, > > struct resource *base, unsigned long size); > > struct resource *request_free_mem_region(struct resource *base, > > unsigned long size, const char *name); > > +struct resource *alloc_free_mem_region(struct resource *base, > > + unsigned long size, unsigned long align, const char *name); > > > > static inline void irqresource_disabled(struct resource *res, u32 irq) > > { > > diff --git a/kernel/resource.c b/kernel/resource.c > > index 53a534db350e..9fc990274106 100644 > > --- a/kernel/resource.c > > +++ b/kernel/resource.c > > > > +static bool gfr_continue(struct resource *base, resource_size_t addr, > > + resource_size_t size, unsigned long flags) > > +{ > > + if (flags & GFR_DESCENDING) > > + return addr > size && addr >= base->start; > > + return addr > addr - size && > > Is this checking for wrap around? If so maybe a comment to call that out? Yes, and ok. > > > + addr <= min_t(resource_size_t, base->end, > > + (1ULL << MAX_PHYSMEM_BITS) - 1); > > +} > > + > > +static resource_size_t gfr_next(resource_size_t addr, resource_size_t size, > > + unsigned long flags) > > +{ > > + if (flags & GFR_DESCENDING) > > + return addr - size; > > + return addr + size; > > +} > > + > > +static void remove_free_mem_region(void *_res) > > { > > - resource_size_t end, addr; > > + struct resource *res = _res; > > + > > + if (res->parent) > > + remove_resource(res); > > + free_resource(res); > > +} > > + > > +static struct resource * > > +get_free_mem_region(struct device *dev, struct resource *base, > > + resource_size_t size, const unsigned long align, > > + const char *name, const unsigned long desc, > > + const unsigned long flags) > > +{ > > + resource_size_t addr; > > struct resource *res; > > struct region_devres *dr = NULL; > > > > - size = ALIGN(size, 1UL << PA_SECTION_SHIFT); > > - end = min_t(unsigned long, base->end, (1UL << MAX_PHYSMEM_BITS) - 1); > > - addr = end - size + 1UL; > > + size = ALIGN(size, align); > > > > res = alloc_resource(GFP_KERNEL); > > if (!res) > > return ERR_PTR(-ENOMEM); > > > > - if (dev) { > > + if (dev && (flags & GFR_REQUEST_REGION)) { > > dr = devres_alloc(devm_region_release, > > sizeof(struct region_devres), GFP_KERNEL); > > if (!dr) { > > free_resource(res); > > return ERR_PTR(-ENOMEM); > > } > > + } else if (dev) { > > + if (devm_add_action_or_reset(dev, remove_free_mem_region, res)) > > + return ERR_PTR(-ENOMEM); > > slightly nicer to return whatever value you got back from devm_add_action_or_reset() Yes, but it is known to only return -ENOMEM on failure and saves adding a local @rc variable. > > > } > > > > write_lock(&resource_lock); > > - for (; addr > size && addr >= base->start; addr -= size) { > > - if (__region_intersects(addr, size, 0, IORES_DESC_NONE) != > > - REGION_DISJOINT) > > + for (addr = gfr_start(base, size, align, flags); > > + gfr_continue(base, addr, size, flags); > > + addr = gfr_next(addr, size, flags)) { > > + if (__region_intersects(base, addr, size, 0, IORES_DESC_NONE) != > > + REGION_DISJOINT) > > continue; > > > > - if (__request_region_locked(res, &iomem_resource, addr, size, > > - name, 0)) > > - break; > > + if (flags & GFR_REQUEST_REGION) { > > + if (__request_region_locked(res, &iomem_resource, addr, > > + size, name, 0)) > > + break; > > > > - if (dev) { > > - dr->parent = &iomem_resource; > > - dr->start = addr; > > - dr->n = size; > > - devres_add(dev, dr); > > - } > > + if (dev) { > > + dr->parent = &iomem_resource; > > + dr->start = addr; > > + dr->n = size; > > + devres_add(dev, dr); > > + } > > > > - res->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY; > > - write_unlock(&resource_lock); > > + res->desc = desc; > > + write_unlock(&resource_lock); > > + > > + > > + /* > > + * A driver is claiming this region so revoke any > > + * mappings. > > + */ > > + revoke_iomem(res); > > + } else { > > + res->start = addr; > > + res->end = addr + size - 1; > > + res->name = name; > > + res->desc = desc; > > + res->flags = IORESOURCE_MEM; > > + > > + /* > > + * Only succeed if the resource hosts an exclusive > > + * range after the insert > > + */ > > + if (__insert_resource(base, res) || res->child) > > + break; > > + > > + write_unlock(&resource_lock); > > + } > > > > - /* > > - * A driver is claiming this region so revoke any mappings. > > - */ > > - revoke_iomem(res); > > return res; > > } > > write_unlock(&resource_lock); > > > > - free_resource(res); > > - if (dr) > > + if (flags & GFR_REQUEST_REGION) { > > + free_resource(res); > > devres_free(dr); > > The original if (dr) was unnecessary as devres_free() checks. > > Looking just at this patch it looks like you aren't covering the > corner case of dev == NULL and GFR_REQUEST_REGION. > > Perhaps worth a tiny comment in patch description? (doesn't seem worth > pulling this change out as a precursor given it's so small). > Of add the extra if (dr) back in to 'document' that no change... Added to the changelog: As part of the consolidation of the legacy GFR_REQUEST_REGION case with the new default of just inserting a new resource into the free space some minor cleanups like not checking for NULL before calling devres_free() (which does its own check) is included. > > > > + } else if (dev) > > + devm_release_action(dev, remove_free_mem_region, res); > > > > return ERR_PTR(-ERANGE); > > } > > @@ -1854,18 +1928,48 @@ static struct resource *__request_free_mem_region(struct device *dev, > > struct resource *devm_request_free_mem_region(struct device *dev, > > struct resource *base, unsigned long size) > > { > > - return __request_free_mem_region(dev, base, size, dev_name(dev)); > > + unsigned long flags = GFR_DESCENDING | GFR_REQUEST_REGION; > > + > > + return get_free_mem_region(dev, base, size, GFR_DEFAULT_ALIGN, > > + dev_name(dev), > > + IORES_DESC_DEVICE_PRIVATE_MEMORY, flags); > > } > > EXPORT_SYMBOL_GPL(devm_request_free_mem_region); > > > > struct resource *request_free_mem_region(struct resource *base, > > unsigned long size, const char *name) > > { > > - return __request_free_mem_region(NULL, base, size, name); > > + unsigned long flags = GFR_DESCENDING | GFR_REQUEST_REGION; > > + > > + return get_free_mem_region(NULL, base, size, GFR_DEFAULT_ALIGN, name, > > + IORES_DESC_DEVICE_PRIVATE_MEMORY, flags); > > } > > EXPORT_SYMBOL_GPL(request_free_mem_region); > > > > -#endif /* CONFIG_DEVICE_PRIVATE */ > > +/** > > + * alloc_free_mem_region - find a free region relative to @base > > + * @base: resource that will parent the new resource > > + * @size: size in bytes of memory to allocate from @base > > + * @align: alignment requirements for the allocation > > + * @name: resource name > > + * > > + * Buses like CXL, that can dynamically instantiate new memory regions, > > + * need a method to allocate physical address space for those regions. > > + * Allocate and insert a new resource to cover a free, unclaimed by a > > + * descendant of @base, range in the span of @base. > > + */ > > +struct resource *alloc_free_mem_region(struct resource *base, > Given the extra align parameter, does it make sense to give this a naming > that highlights that vs the other two interfaces above? > > alloc_free_mem_region_aligned() The other variants are also aligned, they just aren't variably aligned, they are implicitly aligned to GFR_DEFAULT_ALIGN. So I think calling this one _aligned() betrays what is happening in the other cases. > > + unsigned long size, unsigned long align, > > + const char *name) > > +{ > > + /* GFR_ASCENDING | GFR_INSERT_RESOURCE */ > > Given those flags don't exist and some fool like me might grep for them > perhaps better to describe it in text > > /* Default of ascending direction and insert resource */ Ok.
