Commit 9b7206bc authored by David Hildenbrand's avatar David Hildenbrand Committed by Wupeng Ma
Browse files

mm/memory_hotplug: extend offline_and_remove_memory() to handle more than one memory block 

mainline inclusion
from mainline-v5.11-rc1
commit 8dc4bb58
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7F3HQ
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8dc4bb58a146655eb057247d7c9d19e73928715b



--------------------------------

virtio-mem soon wants to use offline_and_remove_memory() memory that
exceeds a single Linux memory block (memory_block_size_bytes()). Let's
remove that restriction.

Let's remember the old state and try to restore that if anything goes
wrong. While re-onlining can, in general, fail, it's highly unlikely to
happen (usually only when a notifier fails to allocate memory, and these
are rather rare).

This will be used by virtio-mem to offline+remove memory ranges that are
bigger than a single memory block - for example, with a device block
size of 1 GiB (e.g., gigantic pages in the hypervisor) and a Linux memory
block size of 128MB.

While we could compress the state into 2 bit, using 8 bit is much
easier.

This handling is similar, but different to acpi_scan_try_to_offline():

a) We don't try to offline twice. I am not sure if this CONFIG_MEMCG
optimization is still relevant - it should only apply to ZONE_NORMAL
(where we have no guarantees). If relevant, we can always add it.

b) acpi_scan_try_to_offline() simply onlines all memory in case
something goes wrong. It doesn't restore previous online type. Let's do
that, so we won't overwrite what e.g., user space configured.

Reviewed-by: default avatarWei Yang <richard.weiyang@linux.alibaba.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20201112133815.13332-28-david@redhat.com


Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Acked-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarMa Wupeng <mawupeng1@huawei.com>
parent 7ac36644

mm/memory_hotplug.c

+89 −16
Original line number Diff line number Diff line
@@ -1675,39 +1675,112 @@ int remove_memory(int nid, u64 start, u64 size) 
}

EXPORT_SYMBOL_GPL(remove_memory);



static int try_offline_memory_block(struct memory_block *mem, void *arg)

{

	uint8_t online_type = MMOP_ONLINE_KERNEL;

	uint8_t **online_types = arg;

	struct page *page;

	int rc;



	/*

	 * Sense the online_type via the zone of the memory block. Offlining

	 * with multiple zones within one memory block will be rejected

	 * by offlining code ... so we don't care about that.

	 */

	page = pfn_to_online_page(section_nr_to_pfn(mem->start_section_nr));

	if (page && zone_idx(page_zone(page)) == ZONE_MOVABLE)

		online_type = MMOP_ONLINE_MOVABLE;



	rc = device_offline(&mem->dev);

	/*

 * Try to offline and remove a memory block. Might take a long time to

 * finish in case memory is still in use. Primarily useful for memory devices

 * that logically unplugged all memory (so it's no longer in use) and want to

 * offline + remove the memory block.

	 * Default is MMOP_OFFLINE - change it only if offlining succeeded,

	 * so try_reonline_memory_block() can do the right thing.

	 */

	if (!rc)

		**online_types = online_type;



	(*online_types)++;

	/* Ignore if already offline. */

	return rc < 0 ? rc : 0;

}



static int try_reonline_memory_block(struct memory_block *mem, void *arg)

{

	uint8_t **online_types = arg;

	int rc;



	if (**online_types != MMOP_OFFLINE) {

		mem->online_type = **online_types;

		rc = device_online(&mem->dev);

		if (rc < 0)

			pr_warn("%s: Failed to re-online memory: %d",

				__func__, rc);

	}



	/* Continue processing all remaining memory blocks. */

	(*online_types)++;

	return 0;

}



/*

 * Try to offline and remove memory. Might take a long time to finish in case

 * memory is still in use. Primarily useful for memory devices that logically

 * unplugged all memory (so it's no longer in use) and want to offline + remove

 * that memory.

 */

int offline_and_remove_memory(int nid, u64 start, u64 size)

{

	struct memory_block *mem;

	int rc = -EINVAL;

	const unsigned long mb_count = size / memory_block_size_bytes();

	uint8_t *online_types, *tmp;

	int rc;



	if (!IS_ALIGNED(start, memory_block_size_bytes()) ||

	    size != memory_block_size_bytes())

		return rc;

	    !IS_ALIGNED(size, memory_block_size_bytes()) || !size)

		return -EINVAL;



	/*

	 * We'll remember the old online type of each memory block, so we can

	 * try to revert whatever we did when offlining one memory block fails

	 * after offlining some others succeeded.

	 */

	online_types = kmalloc_array(mb_count, sizeof(*online_types),

				     GFP_KERNEL);

	if (!online_types)

		return -ENOMEM;

	/*

	 * Initialize all states to MMOP_OFFLINE, so when we abort processing in

	 * try_offline_memory_block(), we'll skip all unprocessed blocks in

	 * try_reonline_memory_block().

	 */

	memset(online_types, MMOP_OFFLINE, mb_count);



	lock_device_hotplug();

	mem = find_memory_block(__pfn_to_section(PFN_DOWN(start)));

	if (mem)

		rc = device_offline(&mem->dev);

	/* Ignore if the device is already offline. */

	if (rc > 0)

		rc = 0;



	tmp = online_types;

	rc = walk_memory_blocks(start, size, &tmp, try_offline_memory_block);



	/*

	 * In case we succeeded to offline the memory block, remove it.

	 * In case we succeeded to offline all memory, remove it.

	 * This cannot fail as it cannot get onlined in the meantime.

	 */

	if (!rc) {

		rc = try_remove_memory(nid, start, size);

		WARN_ON_ONCE(rc);

		if (rc)

			pr_err("%s: Failed to remove memory: %d", __func__, rc);

	}



	/*

	 * Rollback what we did. While memory onlining might theoretically fail

	 * (nacked by a notifier), it barely ever happens.

	 */

	if (rc) {

		tmp = online_types;

		walk_memory_blocks(start, size, &tmp,

				   try_reonline_memory_block);

	}

	unlock_device_hotplug();



	kfree(online_types);

	return rc;

}

EXPORT_SYMBOL_GPL(offline_and_remove_memory);