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Subject[PATCH v1 06/10] mm/memory_hotplug: onlining pages can only fail due to notifiers
Date
Onlining pages can only fail if a notifier reported a problem (e.g. -ENOMEM).
Remove and restructure error handling. While at it, document how
online_pages() can be used right now.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Reza Arbab <arbab@linux.vnet.ibm.com>
Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
mm/memory_hotplug.c | 47 +++++++++++++++++++++++++++++----------------
1 file changed, 30 insertions(+), 17 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index c971295a1100..8c0b7d85252b 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -902,7 +902,26 @@ static struct zone * __meminit move_pfn_range(int online_type, int nid,
return zone;
}

-/* Must be protected by mem_hotplug_begin() or a device_lock */
+/**
+ * online_pages - online pages in a given range (that are currently offline)
+ * @start_pfn: start pfn of the memory range
+ * @nr_pages: the number of pages
+ * @online_type: how to online pages (esp. to which zone to add them)
+ *
+ * This function onlines the given pages. Usually, any alignemt / size
+ * can be used. However, all pages of memory to be removed later on in
+ * one piece via remove_memory() should be onlined the same way and at
+ * least the first page should be onlined if anything else is onlined.
+ * The zone of the first page is used to fixup zones when removing memory
+ * later on (see __remove_pages()).
+ *
+ * Returns 0 if sucessful, an error code if a memory notifier reported a
+ * problem (e.g. -ENOMEM).
+ *
+ * Bad things will happen if pages in the range are already online.
+ *
+ * Must be protected by mem_hotplug_begin() or a device_lock
+ */
int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_type)
{
unsigned long flags;
@@ -923,8 +942,13 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ

ret = memory_notify(MEM_GOING_ONLINE, &arg);
ret = notifier_to_errno(ret);
- if (ret)
- goto failed_addition;
+ if (ret) {
+ pr_debug("online_pages [mem %#010llx-%#010llx] failed\n",
+ (unsigned long long) pfn << PAGE_SHIFT,
+ (((unsigned long long) pfn + nr_pages) << PAGE_SHIFT) - 1);
+ memory_notify(MEM_CANCEL_ONLINE, &arg);
+ return ret;
+ }

/*
* If this zone is not populated, then it is not in zonelist.
@@ -936,13 +960,9 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
setup_zone_pageset(zone);
}

- ret = walk_system_ram_range(pfn, nr_pages, &onlined_pages,
- online_pages_range);
- if (ret) {
- if (need_zonelists_rebuild)
- zone_pcp_reset(zone);
- goto failed_addition;
- }
+ /* onlining pages cannot fail */
+ walk_system_ram_range(pfn, nr_pages, &onlined_pages,
+ online_pages_range);

zone->present_pages += onlined_pages;

@@ -972,13 +992,6 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
if (onlined_pages)
memory_notify(MEM_ONLINE, &arg);
return 0;
-
-failed_addition:
- pr_debug("online_pages [mem %#010llx-%#010llx] failed\n",
- (unsigned long long) pfn << PAGE_SHIFT,
- (((unsigned long long) pfn + nr_pages) << PAGE_SHIFT) - 1);
- memory_notify(MEM_CANCEL_ONLINE, &arg);
- return ret;
}
#endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */

--
2.17.0
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