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Subject[RFC PATCH 2/4] mm: soft-offline: Change soft_offline_page() interface to tell if the page is split or not.
Date
From: Zi Yan <zi.yan@cs.rutgers.edu>

This prepares for THP migration support. During soft-offlining,
if a THP is migrated without splitting, we need to soft-offline pages
after the THP. Otherwise, we need to soft-offline the next subpage in
that THP.

The new added output parameter in soft_offline_page() help distinguish
the two conditions above. As THPs are split after they are free,
we cannot distinguish the two conditions by examining the soft-offlined
pages.

Signed-off-by: Zi Yan <zi.yan@cs.rutgers.edu>
---
drivers/base/memory.c | 2 +-
include/linux/mm.h | 2 +-
mm/madvise.c | 9 +++++----
mm/memory-failure.c | 11 +++++++----
4 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 4e3b61cda520..3ab25b05d5e8 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -551,7 +551,7 @@ store_soft_offline_page(struct device *dev,
pfn >>= PAGE_SHIFT;
if (!pfn_valid(pfn))
return -ENXIO;
- ret = soft_offline_page(pfn_to_page(pfn), 0);
+ ret = soft_offline_page(pfn_to_page(pfn), 0, NULL);
return ret == 0 ? count : ret;
}

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6f543a47fc92..d392fa090ab5 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2467,7 +2467,7 @@ extern int sysctl_memory_failure_early_kill;
extern int sysctl_memory_failure_recovery;
extern void shake_page(struct page *p, int access);
extern atomic_long_t num_poisoned_pages;
-extern int soft_offline_page(struct page *page, int flags);
+extern int soft_offline_page(struct page *page, int flags, int *split);


/*
diff --git a/mm/madvise.c b/mm/madvise.c
index 49f6774db259..857255db404a 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -634,17 +634,18 @@ static int madvise_inject_error(int behavior,
}

if (behavior == MADV_SOFT_OFFLINE) {
+ int split = 0;
+
pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
page_to_pfn(page), start);

- ret = soft_offline_page(page, MF_COUNT_INCREASED);
+ ret = soft_offline_page(page, MF_COUNT_INCREASED, &split);
if (ret)
return ret;
/*
- * Non hugetlb pages either have PAGE_SIZE
- * or are split into PAGE_SIZE
+ * If the page is split, page_size should be changed.
*/
- if (!PageHuge(page))
+ if (split)
page_size = PAGE_SIZE;
continue;
}
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 8b8ff29412b6..8a9ac6f9e1b0 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1361,7 +1361,7 @@ static void memory_failure_work_func(struct work_struct *work)
if (!gotten)
break;
if (entry.flags & MF_SOFT_OFFLINE)
- soft_offline_page(pfn_to_page(entry.pfn), entry.flags);
+ soft_offline_page(pfn_to_page(entry.pfn), entry.flags, NULL);
else
memory_failure(entry.pfn, entry.trapno, entry.flags);
}
@@ -1678,7 +1678,7 @@ static int __soft_offline_page(struct page *page, int flags)
return ret;
}

-static int soft_offline_in_use_page(struct page *page, int flags)
+static int soft_offline_in_use_page(struct page *page, int flags, int *split)
{
int ret;
struct page *hpage = compound_head(page);
@@ -1694,6 +1694,8 @@ static int soft_offline_in_use_page(struct page *page, int flags)
put_hwpoison_page(hpage);
return -EBUSY;
}
+ if (split)
+ *split = 1;
unlock_page(hpage);
get_hwpoison_page(page);
put_hwpoison_page(hpage);
@@ -1722,6 +1724,7 @@ static void soft_offline_free_page(struct page *page)
* soft_offline_page - Soft offline a page.
* @page: page to offline
* @flags: flags. Same as memory_failure().
+ * @split: output. Tells if page is split or not.
*
* Returns 0 on success, otherwise negated errno.
*
@@ -1740,7 +1743,7 @@ static void soft_offline_free_page(struct page *page)
* 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 soft_offline_page(struct page *page, int flags, int *split)
{
int ret;
unsigned long pfn = page_to_pfn(page);
@@ -1757,7 +1760,7 @@ int soft_offline_page(struct page *page, int flags)
put_online_mems();

if (ret > 0)
- ret = soft_offline_in_use_page(page, flags);
+ ret = soft_offline_in_use_page(page, flags, split);
else if (ret == 0)
soft_offline_free_page(page);

--
2.13.2
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