From: David Hildenbrand david@redhat.com

mainline inclusion from mainline-v5.11-rc1 commit 8dc4bb58a146655eb057247d7c9d19e73928715b 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/?i...

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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: Wei 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: David Hildenbrand david@redhat.com Link: https://lore.kernel.org/r/20201112133815.13332-28-david@redhat.com Signed-off-by: Michael S. Tsirkin mst@redhat.com Acked-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Ma Wupeng mawupeng1@huawei.com --- mm/memory_hotplug.c | 105 +++++++++++++++++++++++++++++++++++++------- 1 file changed, 89 insertions(+), 16 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index d2dd2bfcaac3..203c4eb59557 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -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); + /* + * 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 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. + * 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);