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From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org, virtio-dev@lists.oasis-open.org,
	virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
	Michal Hocko <mhocko@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Michael S . Tsirkin" <mst@redhat.com>,
	David Hildenbrand <david@redhat.com>,
	Oscar Salvador <osalvador@suse.com>,
	Michal Hocko <mhocko@suse.com>,
	Pavel Tatashin <pasha.tatashin@soleen.com>,
	Wei Yang <richard.weiyang@gmail.com>,
	Dan Williams <dan.j.williams@intel.com>, Qian Cai <cai@lca.pw>
Subject: [PATCH v2 07/10] mm/memory_hotplug: Introduce offline_and_remove_memory()
Date: Wed, 11 Mar 2020 18:14:19 +0100	[thread overview]
Message-ID: <20200311171422.10484-8-david@redhat.com> (raw)
In-Reply-To: <20200311171422.10484-1-david@redhat.com>

virtio-mem wants to offline and remove a memory block once it unplugged
all subblocks (e.g., using alloc_contig_range()). Let's provide
an interface to do that from a driver. virtio-mem already supports to
offline partially unplugged memory blocks. Offlining a fully unplugged
memory block will not require to migrate any pages. All unplugged
subblocks are PageOffline() and have a reference count of 0 - so
offlining code will simply skip them.

All we need is an interface to offline and remove the memory from kernel
module context, where we don't have access to the memory block devices
(esp. find_memory_block() and device_offline()) and the device hotplug
lock.

To keep things simple, allow to only work on a single memory block.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Oscar Salvador <osalvador@suse.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Qian Cai <cai@lca.pw>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 include/linux/memory_hotplug.h |  1 +
 mm/memory_hotplug.c            | 37 ++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index f4d59155f3d4..a98aa16dbfa1 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -311,6 +311,7 @@ extern void try_offline_node(int nid);
 extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
 extern int remove_memory(int nid, u64 start, u64 size);
 extern void __remove_memory(int nid, u64 start, u64 size);
+extern int offline_and_remove_memory(int nid, u64 start, u64 size);
 
 #else
 static inline bool is_mem_section_removable(unsigned long pfn,
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index ab1c31e67fd1..d0d337918a15 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1818,4 +1818,41 @@ int remove_memory(int nid, u64 start, u64 size)
 	return rc;
 }
 EXPORT_SYMBOL_GPL(remove_memory);
+
+/*
+ * 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.
+ */
+int offline_and_remove_memory(int nid, u64 start, u64 size)
+{
+	struct memory_block *mem;
+	int rc = -EINVAL;
+
+	if (!IS_ALIGNED(start, memory_block_size_bytes()) ||
+	    size != memory_block_size_bytes())
+		return rc;
+
+	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;
+
+	/*
+	 * In case we succeeded to offline the memory block, 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);
+	}
+	unlock_device_hotplug();
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(offline_and_remove_memory);
 #endif /* CONFIG_MEMORY_HOTREMOVE */
-- 
2.24.1


  parent reply	other threads:[~2020-03-11 17:16 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-11 17:14 [PATCH v2 00/10] virtio-mem: paravirtualized memory David Hildenbrand
2020-03-11 17:14 ` [PATCH v2 01/10] virtio-mem: Paravirtualized memory hotplug David Hildenbrand
2020-04-15  5:59   ` Pankaj Gupta
2020-03-11 17:14 ` [PATCH v2 02/10] virtio-mem: Allow to specify an ACPI PXM as nid David Hildenbrand
2020-03-30 11:04   ` Pankaj Gupta
2020-03-11 17:14 ` [PATCH v2 03/10] virtio-mem: Paravirtualized memory hotunplug part 1 David Hildenbrand
2020-03-11 17:14 ` [PATCH v2 04/10] virtio-mem: Paravirtualized memory hotunplug part 2 David Hildenbrand
2020-03-11 17:14 ` [PATCH v2 05/10] mm: Allow to offline unmovable PageOffline() pages via MEM_GOING_OFFLINE David Hildenbrand
2020-04-14 16:34   ` Michael S. Tsirkin
2020-04-15  0:32     ` Andrew Morton
2020-03-11 17:14 ` [PATCH v2 06/10] virtio-mem: Allow to offline partially unplugged memory blocks David Hildenbrand
2020-03-11 17:14 ` David Hildenbrand [this message]
2020-03-11 17:19   ` [PATCH v2 07/10] mm/memory_hotplug: Introduce offline_and_remove_memory() David Hildenbrand
2020-04-14 16:35     ` Michael S. Tsirkin
2020-04-15  0:30       ` Andrew Morton
2020-04-15  7:35   ` Pankaj Gupta
2020-03-11 17:14 ` [PATCH v2 08/10] virtio-mem: Offline and remove completely unplugged memory blocks David Hildenbrand
2020-04-15  7:42   ` Pankaj Gupta
2020-03-11 17:14 ` [PATCH v2 09/10] virtio-mem: Better retry handling David Hildenbrand
2020-03-11 17:14 ` [PATCH v2 10/10] MAINTAINERS: Add myself as virtio-mem maintainer David Hildenbrand
2020-03-27 16:58 ` [PATCH v2 00/10] virtio-mem: paravirtualized memory Pankaj Gupta
2020-03-27 17:03   ` David Hildenbrand
2020-03-27 17:07     ` David Hildenbrand
2020-03-29 15:41     ` Pankaj Gupta
2020-03-30  8:42       ` David Hildenbrand
2020-03-29 12:42 ` Michael S. Tsirkin
2020-03-30  8:16   ` David Hildenbrand
2020-04-14  9:15   ` David Hildenbrand
2020-04-14 16:28     ` Michael S. Tsirkin
2020-04-14 18:39       ` David Hildenbrand

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