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authorDavid Hildenbrand <david@redhat.com>2020-10-15 20:08:49 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-10-16 11:11:18 -0700
commit9ca6551ee24368a4d2b09566ea4d10fe87860379 (patch)
tree20c9b1243ffac81a6d13a6a919f0f2ad8da74f8f /kernel
parentb6117199787c60539105d2de0d010146e8396fc3 (diff)
downloadlinux-9ca6551ee24368a4d2b09566ea4d10fe87860379.tar.bz2
mm/memory_hotplug: MEMHP_MERGE_RESOURCE to specify merging of System RAM resources
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 <david@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Kees Cook <keescook@chromium.org> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: Stephen Hemminger <sthemmin@microsoft.com> Cc: Wei Liu <wei.liu@kernel.org> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Juergen Gross <jgross@suse.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Roger Pau Monné <roger.pau@citrix.com> Cc: Julien Grall <julien@xen.org> Cc: Baoquan He <bhe@redhat.com> Cc: Wei Yang <richardw.yang@linux.intel.com> Cc: Anton Blanchard <anton@ozlabs.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Len Brown <lenb@kernel.org> Cc: Leonardo Bras <leobras.c@gmail.com> Cc: Libor Pechacek <lpechacek@suse.cz> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Nathan Lynch <nathanl@linux.ibm.com> Cc: "Oliver O'Halloran" <oohall@gmail.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Pingfan Liu <kernelfans@gmail.com> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Link: https://lkml.kernel.org/r/20200911103459.10306-6-david@redhat.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/resource.c60
1 files changed, 60 insertions, 0 deletions
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
*/