+ mm-reinititalise-user-and-admin-reserves-if-memory-is-added-or-removed.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: mm: reinititalise user and admin reserves if memory is added or removed
has been added to the -mm tree.  Its filename is
     mm-reinititalise-user-and-admin-reserves-if-memory-is-added-or-removed.patch

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------------------------------------------------------
From: Andrew Shewmaker <agshew@gmail.com>
Subject: mm: reinititalise user and admin reserves if memory is added or removed

Alter the admin and user reserves of the previous patches in this series
when memory is added or removed.

If memory is added and the reserves have been eliminated or increased
above the default max, then we'll trust the admin.

If memory is removed and there isn't enough free memory, then we need to
reset the reserves.

Otherwise keep the reserve set by the admin.

The reserve reset code is the same as the reserve initialization code.

I tested hot addition and removal by triggering it via sysfs.  The
reserves shrunk when they were set high and memory was removed.  They were
reset higher when memory was added again.

Signed-off-by: Andrew Shewmaker <agshew@gmail.com>
Cc: <linux-mm@kvack.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/mmap.c |   63 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

diff -puN mm/mmap.c~mm-reinititalise-user-and-admin-reserves-if-memory-is-added-or-removed mm/mmap.c
--- a/mm/mmap.c~mm-reinititalise-user-and-admin-reserves-if-memory-is-added-or-removed
+++ a/mm/mmap.c
@@ -33,6 +33,8 @@
 #include <linux/uprobes.h>
 #include <linux/rbtree_augmented.h>
 #include <linux/sched/sysctl.h>
+#include <linux/notifier.h>
+#include <linux/memory.h>
 
 #include <asm/uaccess.h>
 #include <asm/cacheflush.h>
@@ -3141,3 +3143,64 @@ int __meminit init_admin_reserve(void)
 	return 0;
 }
 module_init(init_admin_reserve)
+
+/*
+ * Reinititalise user and admin reserves if memory is added or removed.
+ *
+ * If memory is added and the reserves have been eliminated or increased above
+ * the default max, then we'll trust the admin.
+ *
+ * If memory is removed and there isn't enough free memory, then we
+ * need to reset the reserves.
+ *
+ * Otherwise keep the reserve set by the admin.
+ */
+static int reserve_mem_notifier(struct notifier_block *nb,
+			     unsigned long action, void *data)
+{
+	unsigned long tmp, free_kbytes;
+
+	switch (action) {
+	case MEM_ONLINE:
+		tmp = sysctl_user_reserve_kbytes;
+		if (0 < tmp && tmp < (1UL << 17))
+			init_user_reserve();
+
+		tmp = sysctl_admin_reserve_kbytes;
+		if (0 < tmp && tmp < (1UL << 13))
+			init_admin_reserve();
+
+		break;
+	case MEM_OFFLINE:
+		free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
+
+		if (sysctl_user_reserve_kbytes > free_kbytes) {
+			init_user_reserve();
+			pr_info("vm.user_reserve_kbytes reset to %lu\n",
+				sysctl_user_reserve_kbytes);
+		}
+
+		if (sysctl_admin_reserve_kbytes > free_kbytes) {
+			init_admin_reserve();
+			pr_info("vm.admin_reserve_kbytes reset to %lu\n",
+				sysctl_admin_reserve_kbytes);
+		}
+		break;
+	default:
+		break;
+	}
+	return NOTIFY_OK;
+}
+
+static struct notifier_block reserve_mem_nb = {
+	.notifier_call = reserve_mem_notifier,
+};
+
+int __meminit init_reserve_notifier(void)
+{
+	if (register_memory_notifier(&reserve_mem_nb))
+		printk("Failed registering memory add/remove notifier for admin reserve");
+
+	return 0;
+}
+module_init(init_reserve_notifier)
_

Patches currently in -mm which might be from agshew@gmail.com are

include-linux-memoryh-implement-register_hotmemory_notifier.patch
mm-limit-growth-of-3%-hardcoded-other-user-reserve.patch
mm-replace-hardcoded-3%-with-admin_reserve_pages-knob.patch
mm-reinititalise-user-and-admin-reserves-if-memory-is-added-or-removed.patch
mm-reinititalise-user-and-admin-reserves-if-memory-is-added-or-removed-fix.patch

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