[Xen-devel] [PATCH 3/3] drivers/xen/balloon.c: Xen memory balloon driver with memory hotplug support

[Daniel Kiper <dkiper@xxxxxxxxxxxx>]

Features and fixes:
  - new version of memory hotplug patch which supports
    among others memory allocation policies during errors
    (try until success or stop at first error),
  - this version of patch was tested with tmem
    (selfballooning and frontswap) and works
    very well with it,
  - some other minor fixes.

Signed-off-by: Daniel Kiper <dkiper@xxxxxxxxxxxx>
---
 drivers/xen/Kconfig   |   10 ++
 drivers/xen/balloon.c |  222 ++++++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 221 insertions(+), 11 deletions(-)

diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index 60d71e9..ada8ef5 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -9,6 +9,16 @@ config XEN_BALLOON
          the system to expand the domain's memory allocation, or alternatively
          return unneeded memory to the system.
 
+config XEN_BALLOON_MEMORY_HOTPLUG
+       bool "Xen memory balloon driver with memory hotplug support"
+       default n
+       depends on XEN_BALLOON && MEMORY_HOTPLUG
+       help
+         Xen memory balloon driver with memory hotplug support allows expanding
+         memory available for the system above limit declared at system 
startup.
+         It is very useful on critical systems which require long run without
+         rebooting.
+
 config XEN_SCRUB_PAGES
        bool "Scrub pages before returning them to system"
        depends on XEN_BALLOON
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 06dbdad..69d9367 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -6,6 +6,7 @@
  * Copyright (c) 2003, B Dragovic
  * Copyright (c) 2003-2004, M Williamson, K Fraser
  * Copyright (c) 2005 Dan M. Smith, IBM Corporation
+ * Copyright (c) 2010 Daniel Kiper
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License version 2
@@ -44,6 +45,7 @@
 #include <linux/list.h>
 #include <linux/sysdev.h>
 #include <linux/gfp.h>
+#include <linux/memory.h>
 
 #include <asm/page.h>
 #include <asm/pgalloc.h>
@@ -65,6 +67,9 @@
 
 #define BALLOON_CLASS_NAME "xen_memory"
 
+#define MH_POLICY_TRY_UNTIL_SUCCESS    0
+#define MH_POLICY_STOP_AT_FIRST_ERROR  1
+
 struct balloon_stats {
        /* We aim for 'current allocation' == 'target allocation'. */
        unsigned long current_pages;
@@ -74,6 +79,10 @@ struct balloon_stats {
        unsigned long balloon_high;
        unsigned long schedule_delay;
        unsigned long max_schedule_delay;
+#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
+       unsigned long boot_max_pfn;
+       unsigned long mh_policy;
+#endif
 };
 
 static DEFINE_MUTEX(balloon_mutex);
@@ -193,17 +202,194 @@ static void update_schedule_delay(int cmd)
        balloon_stats.schedule_delay = new_schedule_delay;
 }
 
-static unsigned long current_target(void)
+#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
+static inline int allocate_memory_resource(struct resource **r, unsigned long 
nr_pages)
+{
+       int rc;
+       resource_size_t r_min, r_size;
+
+       /*
+        * Look for first unused memory region starting at page
+        * boundary. Skip last memory section created at boot time
+        * becuase it may contains unused memory pages with PG_reserved
+        * bit not set (online_pages require PG_reserved bit set).
+        */
+
+       *r = kzalloc(sizeof(struct resource), GFP_KERNEL);
+
+       if (!*r)
+               return -ENOMEM;
+
+       (*r)->name = "System RAM";
+       (*r)->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
+       r_min = 
PFN_PHYS(section_nr_to_pfn(pfn_to_section_nr(balloon_stats.boot_max_pfn) + 1));
+       r_size = nr_pages << PAGE_SHIFT;
+
+       rc = allocate_resource(&iomem_resource, *r, r_size, r_min,
+                                       ULONG_MAX, PAGE_SIZE, NULL, NULL);
+
+       if (rc < 0) {
+               kfree(*r);
+               *r = NULL;
+       }
+
+       return rc;
+}
+
+static inline void adjust_memory_resource(struct resource **r, unsigned long 
nr_pages)
+{
+       if ((*r)->end + 1 - (nr_pages << PAGE_SHIFT) == (*r)->start) {
+               BUG_ON(release_resource(*r) < 0);
+               kfree(*r);
+               *r = NULL;
+               return;
+       }
+
+       BUG_ON(adjust_resource(*r, (*r)->start, (*r)->end + 1 - (*r)->start -
+                               (nr_pages << PAGE_SHIFT)) < 0);
+}
+
+static inline int allocate_additional_memory(struct resource *r, unsigned long 
nr_pages)
+{
+       int rc;
+       struct xen_memory_reservation reservation = {
+               .address_bits = 0,
+               .extent_order = 0,
+               .domid        = DOMID_SELF
+       };
+       unsigned long flags, i, pfn, pfn_start;
+
+       if (!nr_pages)
+               return 0;
+
+       pfn_start = PFN_UP(r->end) - nr_pages;
+
+       if (nr_pages > ARRAY_SIZE(frame_list))
+               nr_pages = ARRAY_SIZE(frame_list);
+
+       for (i = 0, pfn = pfn_start; i < nr_pages; ++i, ++pfn)
+               frame_list[i] = pfn;
+
+       set_xen_guest_handle(reservation.extent_start, frame_list);
+       reservation.nr_extents = nr_pages;
+
+       spin_lock_irqsave(&xen_reservation_lock, flags);
+
+       rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
+
+       if (rc <= 0)
+               return (rc < 0) ? rc : -ENOMEM;
+
+       for (i = 0, pfn = pfn_start; i < rc; ++i, ++pfn) {
+               BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
+                      phys_to_machine_mapping_valid(pfn));
+               set_phys_to_machine(pfn, frame_list[i]);
+       }
+
+       spin_unlock_irqrestore(&xen_reservation_lock, flags);
+
+       return rc;
+}
+
+static inline void hotplug_allocated_memory(struct resource **r)
 {
-       unsigned long target = balloon_stats.target_pages;
+       int nid, rc;
+       resource_size_t r_size;
+       struct memory_block *mem;
+       unsigned long pfn;
+
+       r_size = (*r)->end + 1 - (*r)->start;
+       nid = memory_add_physaddr_to_nid((*r)->start);
+
+       rc = add_registered_memory(nid, (*r)->start, r_size);
+
+       if (rc) {
+               pr_err("%s: add_registered_memory: Memory hotplug failed: %i\n",
+                       __func__, rc);
+               balloon_stats.target_pages = balloon_stats.current_pages;
+               *r = NULL;
+               return;
+       }
+
+       if (xen_pv_domain())
+               for (pfn = PFN_DOWN((*r)->start); pfn < PFN_UP((*r)->end); 
++pfn)
+                       if (!PageHighMem(pfn_to_page(pfn)))
+                               BUG_ON(HYPERVISOR_update_va_mapping(
+                                       (unsigned long)__va(pfn << PAGE_SHIFT),
+                                       mfn_pte(pfn_to_mfn(pfn), PAGE_KERNEL), 
0));
+
+       rc = online_pages(PFN_DOWN((*r)->start), r_size >> PAGE_SHIFT);
+
+       if (rc) {
+               pr_err("%s: online_pages: Failed: %i\n", __func__, rc);
+               balloon_stats.target_pages = balloon_stats.current_pages;
+               *r = NULL;
+               return;
+       }
+
+       for (pfn = PFN_DOWN((*r)->start); pfn < PFN_UP((*r)->end); pfn += 
PAGES_PER_SECTION) {
+               mem = find_memory_block(__pfn_to_section(pfn));
+               BUG_ON(!mem);
+               BUG_ON(!present_section_nr(mem->phys_index));
+               mutex_lock(&mem->state_mutex);
+               mem->state = MEM_ONLINE;
+               mutex_unlock(&mem->state_mutex);
+       }
+
+       balloon_stats.current_pages += r_size >> PAGE_SHIFT;
+
+       *r = NULL;
+}
+
+static inline int request_additional_memory(long credit)
+{
+       int rc;
+       static struct resource *r;
+       static unsigned long pages_left;
+
+       if ((credit <= 0 || balloon_stats.balloon_low ||
+                               balloon_stats.balloon_high) && !r)
+               return 0;
 
-       target = min(target,
-                    balloon_stats.current_pages +
-                    balloon_stats.balloon_low +
-                    balloon_stats.balloon_high);
+       if (!r) {
+               rc = allocate_memory_resource(&r, credit);
 
-       return target;
+               if (rc)
+                       return rc;
+
+               pages_left = credit;
+       }
+
+       rc = allocate_additional_memory(r, pages_left);
+
+       if (rc < 0) {
+               if (balloon_stats.mh_policy == MH_POLICY_TRY_UNTIL_SUCCESS)
+                       return rc;
+
+               adjust_memory_resource(&r, pages_left);
+
+               if (!r)
+                       return rc;
+       } else {
+               pages_left -= rc;
+
+               if (pages_left)
+                       return 1;
+       }
+
+       hotplug_allocated_memory(&r);
+
+       return 0;
 }
+#else
+static inline int request_additional_memory(long credit)
+{
+       if (balloon_stats.balloon_low && balloon_stats.balloon_high &&
+                       balloon_stats.target_pages > 
balloon_stats.current_pages)
+               balloon_stats.target_pages = balloon_stats.current_pages;
+       return 0;
+}
+#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
 
 static int increase_reservation(unsigned long nr_pages)
 {
@@ -348,13 +534,13 @@ static int decrease_reservation(unsigned long nr_pages)
  */
 static void balloon_process(struct work_struct *work)
 {
-       int rc, state = 0;
+       int rc, state;
        long credit;
 
        mutex_lock(&balloon_mutex);
 
        do {
-               credit = current_target() - balloon_stats.current_pages;
+               credit = balloon_stats.target_pages - 
balloon_stats.current_pages;
 
                /*
                 * state > 0: hungry,
@@ -362,7 +548,9 @@ static void balloon_process(struct work_struct *work)
                 * state < 0: error, go to sleep.
                 */
 
-               if (credit > 0) {
+               state = request_additional_memory(credit);
+
+               if (credit > 0 && !state) {
                        rc = increase_reservation(credit);
                        state = (rc < 0) ? rc : state;
                }
@@ -454,6 +642,11 @@ static int __init balloon_init(void)
        balloon_stats.schedule_delay = 1;
        balloon_stats.max_schedule_delay = 32;
 
+#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
+       balloon_stats.boot_max_pfn = max_pfn;
+       balloon_stats.mh_policy = MH_POLICY_STOP_AT_FIRST_ERROR;
+#endif
+
        register_balloon(&balloon_sysdev);
 
        /* Initialise the balloon with excess memory space. */
@@ -497,6 +690,10 @@ BALLOON_SHOW(high_kb, "%lu\n", 
PAGES2KB(balloon_stats.balloon_high));
 static SYSDEV_ULONG_ATTR(schedule_delay, 0644, balloon_stats.schedule_delay);
 static SYSDEV_ULONG_ATTR(max_schedule_delay, 0644, 
balloon_stats.max_schedule_delay);
 
+#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
+static SYSDEV_ULONG_ATTR(memory_hotplug_policy, 0644, balloon_stats.mh_policy);
+#endif
+
 static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute 
*attr,
                              char *buf)
 {
@@ -559,7 +756,10 @@ static struct sysdev_attribute *balloon_attrs[] = {
        &attr_target_kb,
        &attr_target,
        &attr_schedule_delay.attr,
-       &attr_max_schedule_delay.attr
+       &attr_max_schedule_delay.attr,
+#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
+       &attr_memory_hotplug_policy.attr
+#endif
 };
 
 static struct attribute *balloon_info_attrs[] = {
-- 
1.4.4.4


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