From 9ca6551ee24368a4d2b09566ea4d10fe87860379 Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Thu, 15 Oct 2020 20:08:49 -0700 Subject: mm/memory_hotplug: MEMHP_MERGE_RESOURCE to specify merging of System RAM resources MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Some add_memory*() users add memory in small, contiguous memory blocks. Examples include virtio-mem, hyper-v balloon, and the XEN balloon. This can quickly result in a lot of memory resources, whereby the actual resource boundaries are not of interest (e.g., it might be relevant for DIMMs, exposed via /proc/iomem to user space). We really want to merge added resources in this scenario where possible. Let's provide a flag (MEMHP_MERGE_RESOURCE) to specify that a resource either created within add_memory*() or passed via add_memory_resource() shall be marked mergeable and merged with applicable siblings. To implement that, we need a kernel/resource interface to mark selected System RAM resources mergeable (IORESOURCE_SYSRAM_MERGEABLE) and trigger merging. Note: We really want to merge after the whole operation succeeded, not directly when adding a resource to the resource tree (it would break add_memory_resource() and require splitting resources again when the operation failed - e.g., due to -ENOMEM). Signed-off-by: David Hildenbrand Signed-off-by: Andrew Morton Reviewed-by: Pankaj Gupta Cc: Michal Hocko Cc: Dan Williams Cc: Jason Gunthorpe Cc: Kees Cook Cc: Ard Biesheuvel Cc: Thomas Gleixner Cc: "K. Y. Srinivasan" Cc: Haiyang Zhang Cc: Stephen Hemminger Cc: Wei Liu Cc: Boris Ostrovsky Cc: Juergen Gross Cc: Stefano Stabellini Cc: Roger Pau Monné Cc: Julien Grall Cc: Baoquan He Cc: Wei Yang Cc: Anton Blanchard Cc: Benjamin Herrenschmidt Cc: Christian Borntraeger Cc: Dave Jiang Cc: Eric Biederman Cc: Greg Kroah-Hartman Cc: Heiko Carstens Cc: Jason Wang Cc: Len Brown Cc: Leonardo Bras Cc: Libor Pechacek Cc: Michael Ellerman Cc: "Michael S. Tsirkin" Cc: Nathan Lynch Cc: "Oliver O'Halloran" Cc: Paul Mackerras Cc: Pingfan Liu Cc: "Rafael J. Wysocki" Cc: Vasily Gorbik Cc: Vishal Verma Link: https://lkml.kernel.org/r/20200911103459.10306-6-david@redhat.com Signed-off-by: Linus Torvalds --- kernel/resource.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 60 insertions(+) (limited to 'kernel') diff --git a/kernel/resource.c b/kernel/resource.c index 4c1c487abbfb..92026827d95b 100644 --- a/kernel/resource.c +++ b/kernel/resource.c @@ -1363,6 +1363,66 @@ retry: } #endif /* CONFIG_MEMORY_HOTREMOVE */ +#ifdef CONFIG_MEMORY_HOTPLUG +static bool system_ram_resources_mergeable(struct resource *r1, + struct resource *r2) +{ + /* We assume either r1 or r2 is IORESOURCE_SYSRAM_MERGEABLE. */ + return r1->flags == r2->flags && r1->end + 1 == r2->start && + r1->name == r2->name && r1->desc == r2->desc && + !r1->child && !r2->child; +} + +/* + * merge_system_ram_resource - mark the System RAM resource mergeable and try to + * merge it with adjacent, mergeable resources + * @res: resource descriptor + * + * This interface is intended for memory hotplug, whereby lots of contiguous + * system ram resources are added (e.g., via add_memory*()) by a driver, and + * the actual resource boundaries are not of interest (e.g., it might be + * relevant for DIMMs). Only resources that are marked mergeable, that have the + * same parent, and that don't have any children are considered. All mergeable + * resources must be immutable during the request. + * + * Note: + * - The caller has to make sure that no pointers to resources that are + * marked mergeable are used anymore after this call - the resource might + * be freed and the pointer might be stale! + * - release_mem_region_adjustable() will split on demand on memory hotunplug + */ +void merge_system_ram_resource(struct resource *res) +{ + const unsigned long flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY; + struct resource *cur; + + if (WARN_ON_ONCE((res->flags & flags) != flags)) + return; + + write_lock(&resource_lock); + res->flags |= IORESOURCE_SYSRAM_MERGEABLE; + + /* Try to merge with next item in the list. */ + cur = res->sibling; + if (cur && system_ram_resources_mergeable(res, cur)) { + res->end = cur->end; + res->sibling = cur->sibling; + free_resource(cur); + } + + /* Try to merge with previous item in the list. */ + cur = res->parent->child; + while (cur && cur->sibling != res) + cur = cur->sibling; + if (cur && system_ram_resources_mergeable(cur, res)) { + cur->end = res->end; + cur->sibling = res->sibling; + free_resource(res); + } + write_unlock(&resource_lock); +} +#endif /* CONFIG_MEMORY_HOTPLUG */ + /* * Managed region resource */ -- cgit v1.2.3-70-g09d2