Commit 9ca6551e authored by David Hildenbrand's avatar David Hildenbrand Committed by Linus Torvalds
Browse files

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: default avatarDavid Hildenbrand <david@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarPankaj 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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b6117199

include/linux/ioport.h

+4 −0
Original line number Diff line number Diff line
@@ -60,6 +60,7 @@ struct resource { 


/* IORESOURCE_SYSRAM specific bits. */

#define IORESOURCE_SYSRAM_DRIVER_MANAGED	0x02000000 /* Always detected via a driver. */

#define IORESOURCE_SYSRAM_MERGEABLE		0x04000000 /* Resource can be merged. */



#define IORESOURCE_EXCLUSIVE	0x08000000	/* Userland may not map this resource */
@@ -253,6 +254,9 @@ extern void __release_region(struct resource *, resource_size_t, 
extern void release_mem_region_adjustable(struct resource *, resource_size_t,

					  resource_size_t);

#endif

#ifdef CONFIG_MEMORY_HOTPLUG

extern void merge_system_ram_resource(struct resource *res);

#endif



/* Wrappers for managed devices */

struct device;

include/linux/memory_hotplug.h

+7 −0
Original line number Diff line number Diff line
@@ -62,6 +62,13 @@ typedef int __bitwise mhp_t; 


/* No special request */

#define MHP_NONE		((__force mhp_t)0)

/*

 * Allow merging of the added System RAM resource with adjacent,

 * mergeable resources. After a successful call to add_memory_resource()

 * with this flag set, the resource pointer must no longer be used as it

 * might be stale, or the resource might have changed.

 */

#define MEMHP_MERGE_RESOURCE	((__force mhp_t)BIT(0))



/*

 * Extended parameters for memory hotplug:

kernel/resource.c

+60 −0
Original line number Diff line number Diff line
@@ -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

 */

mm/memory_hotplug.c

+7 −0
Original line number Diff line number Diff line
@@ -1103,6 +1103,13 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) 
	/* device_online() will take the lock when calling online_pages() */

	mem_hotplug_done();



	/*

	 * In case we're allowed to merge the resource, flag it and trigger

	 * merging now that adding succeeded.

	 */

	if (mhp_flags & MEMHP_MERGE_RESOURCE)

		merge_system_ram_resource(res);



	/* online pages if requested */

	if (memhp_default_online_type != MMOP_OFFLINE)

		walk_memory_blocks(start, size, NULL, online_memory_block);

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