Merge branch 'wip-2.6.34' into old-private-masterarchived-private-master

1 files changed, 521 insertions, 58 deletions

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index dacc64183874..620b0b461593 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -34,12 +34,17 @@
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/page-flags.h>
+#include <linux/kernel-page-flags.h>
 #include <linux/sched.h>
 #include <linux/ksm.h>
 #include <linux/rmap.h>
 #include <linux/pagemap.h>
 #include <linux/swap.h>
 #include <linux/backing-dev.h>
+#include <linux/migrate.h>
+#include <linux/page-isolation.h>
+#include <linux/suspend.h>
+#include <linux/slab.h>
 #include "internal.h"
 
 int sysctl_memory_failure_early_kill __read_mostly = 0;
@@ -48,6 +53,129 @@ int sysctl_memory_failure_recovery __read_mostly = 1;
 
 atomic_long_t mce_bad_pages __read_mostly = ATOMIC_LONG_INIT(0);
 
+#if defined(CONFIG_HWPOISON_INJECT) || defined(CONFIG_HWPOISON_INJECT_MODULE)
+
+u32 hwpoison_filter_enable = 0;
+u32 hwpoison_filter_dev_major = ~0U;
+u32 hwpoison_filter_dev_minor = ~0U;
+u64 hwpoison_filter_flags_mask;
+u64 hwpoison_filter_flags_value;
+EXPORT_SYMBOL_GPL(hwpoison_filter_enable);
+EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major);
+EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
+EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
+EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
+
+static int hwpoison_filter_dev(struct page *p)
+{
+        struct address_space *mapping;
+        dev_t dev;
+
+        if (hwpoison_filter_dev_major == ~0U &&
+            hwpoison_filter_dev_minor == ~0U)
+                return 0;
+
+        /*
+         * page_mapping() does not accept slab page
+         */
+        if (PageSlab(p))
+                return -EINVAL;
+
+        mapping = page_mapping(p);
+        if (mapping == NULL || mapping->host == NULL)
+                return -EINVAL;
+
+        dev = mapping->host->i_sb->s_dev;
+        if (hwpoison_filter_dev_major != ~0U &&
+            hwpoison_filter_dev_major != MAJOR(dev))
+                return -EINVAL;
+        if (hwpoison_filter_dev_minor != ~0U &&
+            hwpoison_filter_dev_minor != MINOR(dev))
+                return -EINVAL;
+
+        return 0;
+}
+
+static int hwpoison_filter_flags(struct page *p)
+{
+        if (!hwpoison_filter_flags_mask)
+                return 0;
+
+        if ((stable_page_flags(p) & hwpoison_filter_flags_mask) ==
+                                    hwpoison_filter_flags_value)
+                return 0;
+        else
+                return -EINVAL;
+}
+
+/*
+ * This allows stress tests to limit test scope to a collection of tasks
+ * by putting them under some memcg. This prevents killing unrelated/important
+ * processes such as /sbin/init. Note that the target task may share clean
+ * pages with init (eg. libc text), which is harmless. If the target task
+ * share _dirty_ pages with another task B, the test scheme must make sure B
+ * is also included in the memcg. At last, due to race conditions this filter
+ * can only guarantee that the page either belongs to the memcg tasks, or is
+ * a freed page.
+ */
+#ifdef  CONFIG_CGROUP_MEM_RES_CTLR_SWAP
+u64 hwpoison_filter_memcg;
+EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
+static int hwpoison_filter_task(struct page *p)
+{
+        struct mem_cgroup *mem;
+        struct cgroup_subsys_state *css;
+        unsigned long ino;
+
+        if (!hwpoison_filter_memcg)
+                return 0;
+
+        mem = try_get_mem_cgroup_from_page(p);
+        if (!mem)
+                return -EINVAL;
+
+        css = mem_cgroup_css(mem);
+        /* root_mem_cgroup has NULL dentries */
+        if (!css->cgroup->dentry)
+                return -EINVAL;
+
+        ino = css->cgroup->dentry->d_inode->i_ino;
+        css_put(css);
+
+        if (ino != hwpoison_filter_memcg)
+                return -EINVAL;
+
+        return 0;
+}
+#else
+static int hwpoison_filter_task(struct page *p) { return 0; }
+#endif
+
+int hwpoison_filter(struct page *p)
+{
+        if (!hwpoison_filter_enable)
+                return 0;
+
+        if (hwpoison_filter_dev(p))
+                return -EINVAL;
+
+        if (hwpoison_filter_flags(p))
+                return -EINVAL;
+
+        if (hwpoison_filter_task(p))
+                return -EINVAL;
+
+        return 0;
+}
+#else
+int hwpoison_filter(struct page *p)
+{
+        return 0;
+}
+#endif
+
+EXPORT_SYMBOL_GPL(hwpoison_filter);
+
 /*
  * Send all the processes who have the page mapped an ``action optional''
  * signal.
@@ -83,6 +211,36 @@ static int kill_proc_ao(struct task_struct *t, unsigned long addr, int trapno,
 }
 
 /*
+ * When a unknown page type is encountered drain as many buffers as possible
+ * in the hope to turn the page into a LRU or free page, which we can handle.
+ */
+void shake_page(struct page *p, int access)
+{
+        if (!PageSlab(p)) {
+                lru_add_drain_all();
+                if (PageLRU(p))
+                        return;
+                drain_all_pages();
+                if (PageLRU(p) || is_free_buddy_page(p))
+                        return;
+        }
+
+        /*
+         * Only all shrink_slab here (which would also
+         * shrink other caches) if access is not potentially fatal.
+         */
+        if (access) {
+                int nr;
+                do {
+                        nr = shrink_slab(1000, GFP_KERNEL, 1000);
+                        if (page_count(p) == 0)
+                                break;
+                } while (nr > 10);
+        }
+}
+EXPORT_SYMBOL_GPL(shake_page);
+
+/*
  * Kill all processes that have a poisoned page mapped and then isolate
  * the page.
  *
@@ -174,10 +332,9 @@ static void kill_procs_ao(struct list_head *to_kill, int doit, int trapno,
         list_for_each_entry_safe (tk, next, to_kill, nd) {
                 if (doit) {
                         /*
-                         * In case something went wrong with munmaping
+                         * In case something went wrong with munmapping
                          * make sure the process doesn't catch the
                          * signal and then access the memory. Just kill it.
-                         * the signal handlers
                          */
                         if (fail || tk->addr_valid == 0) {
                                 printk(KERN_ERR
@@ -227,9 +384,12 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill,
         if (av == NULL) /* Not actually mapped anymore */
                 goto out;
         for_each_process (tsk) {
+                struct anon_vma_chain *vmac;
+
                 if (!task_early_kill(tsk))
                         continue;
-                list_for_each_entry (vma, &av->head, anon_vma_node) {
+                list_for_each_entry(vmac, &av->head, same_anon_vma) {
+                        vma = vmac->vma;
                         if (!page_mapped_in_vma(page, vma))
                                 continue;
                         if (vma->vm_mm == tsk->mm)
@@ -314,33 +474,49 @@ static void collect_procs(struct page *page, struct list_head *tokill)
  */
 
 enum outcome {
-        FAILED,         /* Error handling failed */
+        IGNORED,        /* Error: cannot be handled */
+        FAILED,         /* Error: handling failed */
         DELAYED,        /* Will be handled later */
-        IGNORED,        /* Error safely ignored */
         RECOVERED,      /* Successfully recovered */
 };
 
 static const char *action_name[] = {
+        [IGNORED] = "Ignored",
         [FAILED] = "Failed",
         [DELAYED] = "Delayed",
-        [IGNORED] = "Ignored",
         [RECOVERED] = "Recovered",
 };
 
 /*
- * Error hit kernel page.
- * Do nothing, try to be lucky and not touch this instead. For a few cases we
- * could be more sophisticated.
+ * XXX: It is possible that a page is isolated from LRU cache,
+ * and then kept in swap cache or failed to remove from page cache.
+ * The page count will stop it from being freed by unpoison.
+ * Stress tests should be aware of this memory leak problem.
  */
-static int me_kernel(struct page *p, unsigned long pfn)
+static int delete_from_lru_cache(struct page *p)
 {
-        return DELAYED;
+        if (!isolate_lru_page(p)) {
+                /*
+                 * Clear sensible page flags, so that the buddy system won't
+                 * complain when the page is unpoison-and-freed.
+                 */
+                ClearPageActive(p);
+                ClearPageUnevictable(p);
+                /*
+                 * drop the page count elevated by isolate_lru_page()
+                 */
+                page_cache_release(p);
+                return 0;
+        }
+        return -EIO;
 }
 
 /*
- * Already poisoned page.
+ * Error hit kernel page.
+ * Do nothing, try to be lucky and not touch this instead. For a few cases we
+ * could be more sophisticated.
  */
-static int me_ignore(struct page *p, unsigned long pfn)
+static int me_kernel(struct page *p, unsigned long pfn)
 {
         return IGNORED;
 }
@@ -355,14 +531,6 @@ static int me_unknown(struct page *p, unsigned long pfn)
 }
 
 /*
- * Free memory
- */
-static int me_free(struct page *p, unsigned long pfn)
-{
-        return DELAYED;
-}
-
-/*
  * Clean (or cleaned) page cache page.
  */
 static int me_pagecache_clean(struct page *p, unsigned long pfn)
@@ -371,6 +539,8 @@ static int me_pagecache_clean(struct page *p, unsigned long pfn)
         int ret = FAILED;
         struct address_space *mapping;
 
+        delete_from_lru_cache(p);
+
         /*
          * For anonymous pages we're done the only reference left
          * should be the one m_f() holds.
@@ -500,14 +670,20 @@ static int me_swapcache_dirty(struct page *p, unsigned long pfn)
         /* Trigger EIO in shmem: */
         ClearPageUptodate(p);
 
-        return DELAYED;
+        if (!delete_from_lru_cache(p))
+                return DELAYED;
+        else
+                return FAILED;
 }
 
 static int me_swapcache_clean(struct page *p, unsigned long pfn)
 {
         delete_from_swap_cache(p);
 
-        return RECOVERED;
+        if (!delete_from_lru_cache(p))
+                return RECOVERED;
+        else
+                return FAILED;
 }
 
 /*
@@ -550,7 +726,6 @@ static int me_huge_page(struct page *p, unsigned long pfn)
 #define tail            (1UL << PG_tail)
 #define compound        (1UL << PG_compound)
 #define slab            (1UL << PG_slab)
-#define buddy           (1UL << PG_buddy)
 #define reserved        (1UL << PG_reserved)
 
 static struct page_state {
@@ -559,8 +734,11 @@ static struct page_state {
         char *msg;
         int (*action)(struct page *p, unsigned long pfn);
 } error_states[] = {
-        { reserved,     reserved,       "reserved kernel",      me_ignore },
-        { buddy,        buddy,          "free kernel",  me_free },
+        { reserved,     reserved,       "reserved kernel",      me_kernel },
+        /*
+         * free pages are specially detected outside this table:
+         * PG_buddy pages only make a small fraction of all free pages.
+         */
 
         /*
          * Could in theory check if slab page is free or if we can drop
@@ -582,14 +760,11 @@ static struct page_state {
         { unevict|dirty, unevict|dirty, "unevictable LRU", me_pagecache_dirty},
         { unevict,      unevict,        "unevictable LRU", me_pagecache_clean},
 
-#ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
         { mlock|dirty,  mlock|dirty,    "mlocked LRU",  me_pagecache_dirty },
         { mlock,        mlock,          "mlocked LRU",  me_pagecache_clean },
-#endif
 
         { lru|dirty,    lru|dirty,      "LRU",          me_pagecache_dirty },
         { lru|dirty,    lru,            "clean LRU",    me_pagecache_clean },
-        { swapbacked,   swapbacked,     "anonymous",    me_pagecache_clean },
 
         /*
          * Catchall entry: must be at end.
@@ -597,20 +772,31 @@ static struct page_state {
         { 0,            0,              "unknown page state",   me_unknown },
 };
 
+#undef dirty
+#undef sc
+#undef unevict
+#undef mlock
+#undef writeback
+#undef lru
+#undef swapbacked
+#undef head
+#undef tail
+#undef compound
+#undef slab
+#undef reserved
+
 static void action_result(unsigned long pfn, char *msg, int result)
 {
-        struct page *page = NULL;
-        if (pfn_valid(pfn))
-                page = pfn_to_page(pfn);
+        struct page *page = pfn_to_page(pfn);
 
         printk(KERN_ERR "MCE %#lx: %s%s page recovery: %s\n",
                 pfn,
-                page && PageDirty(page) ? "dirty " : "",
+                PageDirty(page) ? "dirty " : "",
                 msg, action_name[result]);
 }
 
 static int page_action(struct page_state *ps, struct page *p,
-                        unsigned long pfn, int ref)
+                        unsigned long pfn)
 {
         int result;
         int count;
@@ -618,18 +804,22 @@ static int page_action(struct page_state *ps, struct page *p,
         result = ps->action(p, pfn);
         action_result(pfn, ps->msg, result);
 
-        count = page_count(p) - 1 - ref;
-        if (count != 0)
+        count = page_count(p) - 1;
+        if (ps->action == me_swapcache_dirty && result == DELAYED)
+                count--;
+        if (count != 0) {
                 printk(KERN_ERR
                        "MCE %#lx: %s page still referenced by %d users\n",
                        pfn, ps->msg, count);
+                result = FAILED;
+        }
 
         /* Could do more checks here if page looks ok */
         /*
          * Could adjust zone counters here to correct for the missing page.
          */
 
-        return result == RECOVERED ? 0 : -EBUSY;
+        return (result == RECOVERED || result == DELAYED) ? 0 : -EBUSY;
 }
 
 #define N_UNMAP_TRIES 5
@@ -638,7 +828,7 @@ static int page_action(struct page_state *ps, struct page *p,
  * Do all that is necessary to remove user space mappings. Unmap
  * the pages and send SIGBUS to the processes if the data was dirty.
  */
-static void hwpoison_user_mappings(struct page *p, unsigned long pfn,
+static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
                                   int trapno)
 {
         enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
@@ -648,15 +838,18 @@ static void hwpoison_user_mappings(struct page *p, unsigned long pfn,
         int i;
         int kill = 1;
 
-        if (PageReserved(p) || PageCompound(p) || PageSlab(p) || PageKsm(p))
-                return;
+        if (PageReserved(p) || PageSlab(p))
+                return SWAP_SUCCESS;
 
         /*
          * This check implies we don't kill processes if their pages
          * are in the swap cache early. Those are always late kills.
          */
         if (!page_mapped(p))
-                return;
+                return SWAP_SUCCESS;
+
+        if (PageCompound(p) || PageKsm(p))
+                return SWAP_FAIL;
 
         if (PageSwapCache(p)) {
                 printk(KERN_ERR
@@ -667,6 +860,8 @@ static void hwpoison_user_mappings(struct page *p, unsigned long pfn,
         /*
          * Propagate the dirty bit from PTEs to struct page first, because we
          * need this to decide if we should kill or just drop the page.
+         * XXX: the dirty test could be racy: set_page_dirty() may not always
+         * be called inside page lock (it's recommended but not enforced).
          */
         mapping = page_mapping(p);
         if (!PageDirty(p) && mapping && mapping_cap_writeback_dirty(mapping)) {
@@ -718,11 +913,12 @@ static void hwpoison_user_mappings(struct page *p, unsigned long pfn,
          */
         kill_procs_ao(&tokill, !!PageDirty(p), trapno,
                       ret != SWAP_SUCCESS, pfn);
+
+        return ret;
 }
 
-int __memory_failure(unsigned long pfn, int trapno, int ref)
+int __memory_failure(unsigned long pfn, int trapno, int flags)
 {
-        unsigned long lru_flag;
         struct page_state *ps;
         struct page *p;
         int res;
@@ -731,13 +927,15 @@ int __memory_failure(unsigned long pfn, int trapno, int ref)
                 panic("Memory failure from trap %d on page %lx", trapno, pfn);
 
         if (!pfn_valid(pfn)) {
-                action_result(pfn, "memory outside kernel control", IGNORED);
-                return -EIO;
+                printk(KERN_ERR
+                       "MCE %#lx: memory outside kernel control\n",
+                       pfn);
+                return -ENXIO;
         }
 
         p = pfn_to_page(pfn);
         if (TestSetPageHWPoison(p)) {
-                action_result(pfn, "already hardware poisoned", IGNORED);
+                printk(KERN_ERR "MCE %#lx: already hardware poisoned\n", pfn);
                 return 0;
         }
 
@@ -754,9 +952,15 @@ int __memory_failure(unsigned long pfn, int trapno, int ref)
          * In fact it's dangerous to directly bump up page count from 0,
          * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
          */
-        if (!get_page_unless_zero(compound_head(p))) {
-                action_result(pfn, "free or high order kernel", IGNORED);
-                return PageBuddy(compound_head(p)) ? 0 : -EBUSY;
+        if (!(flags & MF_COUNT_INCREASED) &&
+                !get_page_unless_zero(compound_head(p))) {
+                if (is_free_buddy_page(p)) {
+                        action_result(pfn, "free buddy", DELAYED);
+                        return 0;
+                } else {
+                        action_result(pfn, "high order kernel", IGNORED);
+                        return -EBUSY;
+                }
         }
 
         /*
@@ -768,14 +972,19 @@ int __memory_failure(unsigned long pfn, int trapno, int ref)
          * walked by the page reclaim code, however that's not a big loss.
          */
         if (!PageLRU(p))
-                lru_add_drain_all();
-        lru_flag = p->flags & lru;
-        if (isolate_lru_page(p)) {
+                shake_page(p, 0);
+        if (!PageLRU(p)) {
+                /*
+                 * shake_page could have turned it free.
+                 */
+                if (is_free_buddy_page(p)) {
+                        action_result(pfn, "free buddy, 2nd try", DELAYED);
+                        return 0;
+                }
                 action_result(pfn, "non LRU", IGNORED);
                 put_page(p);
                 return -EBUSY;
         }
-        page_cache_release(p);
 
         /*
          * Lock the page and wait for writeback to finish.
@@ -783,26 +992,48 @@ int __memory_failure(unsigned long pfn, int trapno, int ref)
          * and in many cases impossible, so we just avoid it here.
          */
         lock_page_nosync(p);
+
+        /*
+         * unpoison always clear PG_hwpoison inside page lock
+         */
+        if (!PageHWPoison(p)) {
+                printk(KERN_ERR "MCE %#lx: just unpoisoned\n", pfn);
+                res = 0;
+                goto out;
+        }
+        if (hwpoison_filter(p)) {
+                if (TestClearPageHWPoison(p))
+                        atomic_long_dec(&mce_bad_pages);
+                unlock_page(p);
+                put_page(p);
+                return 0;
+        }
+
         wait_on_page_writeback(p);
 
         /*
          * Now take care of user space mappings.
+         * Abort on fail: __remove_from_page_cache() assumes unmapped page.
          */
-        hwpoison_user_mappings(p, pfn, trapno);
+        if (hwpoison_user_mappings(p, pfn, trapno) != SWAP_SUCCESS) {
+                printk(KERN_ERR "MCE %#lx: cannot unmap page, give up\n", pfn);
+                res = -EBUSY;
+                goto out;
+        }
 
         /*
          * Torn down by someone else?
          */
-        if ((lru_flag & lru) && !PageSwapCache(p) && p->mapping == NULL) {
+        if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
                 action_result(pfn, "already truncated LRU", IGNORED);
-                res = 0;
+                res = -EBUSY;
                 goto out;
         }
 
         res = -EBUSY;
         for (ps = error_states;; ps++) {
-                if (((p->flags | lru_flag)& ps->mask) == ps->res) {
-                        res = page_action(ps, p, pfn, ref);
+                if ((p->flags & ps->mask) == ps->res) {
+                        res = page_action(ps, p, pfn);
                         break;
                 }
         }
@@ -833,3 +1064,235 @@ void memory_failure(unsigned long pfn, int trapno)
 {
         __memory_failure(pfn, trapno, 0);
 }
+
+/**
+ * unpoison_memory - Unpoison a previously poisoned page
+ * @pfn: Page number of the to be unpoisoned page
+ *
+ * Software-unpoison a page that has been poisoned by
+ * memory_failure() earlier.
+ *
+ * This is only done on the software-level, so it only works
+ * for linux injected failures, not real hardware failures
+ *
+ * Returns 0 for success, otherwise -errno.
+ */
+int unpoison_memory(unsigned long pfn)
+{
+        struct page *page;
+        struct page *p;
+        int freeit = 0;
+
+        if (!pfn_valid(pfn))
+                return -ENXIO;
+
+        p = pfn_to_page(pfn);
+        page = compound_head(p);
+
+        if (!PageHWPoison(p)) {
+                pr_debug("MCE: Page was already unpoisoned %#lx\n", pfn);
+                return 0;
+        }
+
+        if (!get_page_unless_zero(page)) {
+                if (TestClearPageHWPoison(p))
+                        atomic_long_dec(&mce_bad_pages);
+                pr_debug("MCE: Software-unpoisoned free page %#lx\n", pfn);
+                return 0;
+        }
+
+        lock_page_nosync(page);
+        /*
+         * This test is racy because PG_hwpoison is set outside of page lock.
+         * That's acceptable because that won't trigger kernel panic. Instead,
+         * the PG_hwpoison page will be caught and isolated on the entrance to
+         * the free buddy page pool.
+         */
+        if (TestClearPageHWPoison(p)) {
+                pr_debug("MCE: Software-unpoisoned page %#lx\n", pfn);
+                atomic_long_dec(&mce_bad_pages);
+                freeit = 1;
+        }
+        unlock_page(page);
+
+        put_page(page);
+        if (freeit)
+                put_page(page);
+
+        return 0;
+}
+EXPORT_SYMBOL(unpoison_memory);
+
+static struct page *new_page(struct page *p, unsigned long private, int **x)
+{
+        int nid = page_to_nid(p);
+        return alloc_pages_exact_node(nid, GFP_HIGHUSER_MOVABLE, 0);
+}
+
+/*
+ * Safely get reference count of an arbitrary page.
+ * Returns 0 for a free page, -EIO for a zero refcount page
+ * that is not free, and 1 for any other page type.
+ * For 1 the page is returned with increased page count, otherwise not.
+ */
+static int get_any_page(struct page *p, unsigned long pfn, int flags)
+{
+        int ret;
+
+        if (flags & MF_COUNT_INCREASED)
+                return 1;
+
+        /*
+         * The lock_system_sleep prevents a race with memory hotplug,
+         * because the isolation assumes there's only a single user.
+         * This is a big hammer, a better would be nicer.
+         */
+        lock_system_sleep();
+
+        /*
+         * Isolate the page, so that it doesn't get reallocated if it
+         * was free.
+         */
+        set_migratetype_isolate(p);
+        if (!get_page_unless_zero(compound_head(p))) {
+                if (is_free_buddy_page(p)) {
+                        pr_debug("get_any_page: %#lx free buddy page\n", pfn);
+                        /* Set hwpoison bit while page is still isolated */
+                        SetPageHWPoison(p);
+                        ret = 0;
+                } else {
+                        pr_debug("get_any_page: %#lx: unknown zero refcount page type %lx\n",
+                                pfn, p->flags);
+                        ret = -EIO;
+                }
+        } else {
+                /* Not a free page */
+                ret = 1;
+        }
+        unset_migratetype_isolate(p);
+        unlock_system_sleep();
+        return ret;
+}
+
+/**
+ * soft_offline_page - Soft offline a page.
+ * @page: page to offline
+ * @flags: flags. Same as memory_failure().
+ *
+ * Returns 0 on success, otherwise negated errno.
+ *
+ * Soft offline a page, by migration or invalidation,
+ * without killing anything. This is for the case when
+ * a page is not corrupted yet (so it's still valid to access),
+ * but has had a number of corrected errors and is better taken
+ * out.
+ *
+ * The actual policy on when to do that is maintained by
+ * user space.
+ *
+ * This should never impact any application or cause data loss,
+ * however it might take some time.
+ *
+ * This is not a 100% solution for all memory, but tries to be
+ * ``good enough'' for the majority of memory.
+ */
+int soft_offline_page(struct page *page, int flags)
+{
+        int ret;
+        unsigned long pfn = page_to_pfn(page);
+
+        ret = get_any_page(page, pfn, flags);
+        if (ret < 0)
+                return ret;
+        if (ret == 0)
+                goto done;
+
+        /*
+         * Page cache page we can handle?
+         */
+        if (!PageLRU(page)) {
+                /*
+                 * Try to free it.
+                 */
+                put_page(page);
+                shake_page(page, 1);
+
+                /*
+                 * Did it turn free?
+                 */
+                ret = get_any_page(page, pfn, 0);
+                if (ret < 0)
+                        return ret;
+                if (ret == 0)
+                        goto done;
+        }
+        if (!PageLRU(page)) {
+                pr_debug("soft_offline: %#lx: unknown non LRU page type %lx\n",
+                                pfn, page->flags);
+                return -EIO;
+        }
+
+        lock_page(page);
+        wait_on_page_writeback(page);
+
+        /*
+         * Synchronized using the page lock with memory_failure()
+         */
+        if (PageHWPoison(page)) {
+                unlock_page(page);
+                put_page(page);
+                pr_debug("soft offline: %#lx page already poisoned\n", pfn);
+                return -EBUSY;
+        }
+
+        /*
+         * Try to invalidate first. This should work for
+         * non dirty unmapped page cache pages.
+         */
+        ret = invalidate_inode_page(page);
+        unlock_page(page);
+
+        /*
+         * Drop count because page migration doesn't like raised
+         * counts. The page could get re-allocated, but if it becomes
+         * LRU the isolation will just fail.
+         * RED-PEN would be better to keep it isolated here, but we
+         * would need to fix isolation locking first.
+         */
+        put_page(page);
+        if (ret == 1) {
+                ret = 0;
+                pr_debug("soft_offline: %#lx: invalidated\n", pfn);
+                goto done;
+        }
+
+        /*
+         * Simple invalidation didn't work.
+         * Try to migrate to a new page instead. migrate.c
+         * handles a large number of cases for us.
+         */
+        ret = isolate_lru_page(page);
+        if (!ret) {
+                LIST_HEAD(pagelist);
+
+                list_add(&page->lru, &pagelist);
+                ret = migrate_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL, 0);
+                if (ret) {
+                        pr_debug("soft offline: %#lx: migration failed %d, type %lx\n",
+                                pfn, ret, page->flags);
+                        if (ret > 0)
+                                ret = -EIO;
+                }
+        } else {
+                pr_debug("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n",
+                                pfn, ret, page_count(page), page->flags);
+        }
+        if (ret)
+                return ret;
+
+done:
+        atomic_long_add(1, &mce_bad_pages);
+        SetPageHWPoison(page);
+        /* keep elevated page count for bad page */
+        return ret;
+}