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mm/memory-failure.c: clean up soft_offline_page()
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Currently soft_offline_page() is hard to maintain because it has many
return points and goto statements.  All of this mess come from
get_any_page().

This function should only get page refcount as the name implies, but it
does some page isolating actions like SetPageHWPoison() and dequeuing
hugepage.  This patch corrects it and introduces some internal
subroutines to make soft offlining code more readable and maintainable.

Signed-off-by: Naoya Horiguchi <[email protected]>
Reviewed-by: Andi Kleen <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Wu Fengguang <[email protected]>
Cc: Xishi Qiu <[email protected]>
Cc: Jiang Liu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@torvalds
Naoya Horiguchi authored and torvalds committed Feb 24, 2013
1 parent 293c07e commit af8fae7
Showing 1 changed file with 87 additions and 69 deletions.
156 changes: 87 additions & 69 deletions mm/memory-failure.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1368,7 +1368,7 @@ static struct page *new_page(struct page *p, unsigned long private, int **x)
* 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)
static int __get_any_page(struct page *p, unsigned long pfn, int flags)
{
int ret;

Expand All @@ -1393,11 +1393,9 @@ static int get_any_page(struct page *p, unsigned long pfn, int flags)
if (!get_page_unless_zero(compound_head(p))) {
if (PageHuge(p)) {
pr_info("%s: %#lx free huge page\n", __func__, pfn);
ret = dequeue_hwpoisoned_huge_page(compound_head(p));
ret = 0;
} else if (is_free_buddy_page(p)) {
pr_info("%s: %#lx free buddy page\n", __func__, pfn);
/* Set hwpoison bit while page is still isolated */
SetPageHWPoison(p);
ret = 0;
} else {
pr_info("%s: %#lx: unknown zero refcount page type %lx\n",
Expand All @@ -1413,23 +1411,48 @@ static int get_any_page(struct page *p, unsigned long pfn, int flags)
return ret;
}

static int get_any_page(struct page *page, unsigned long pfn, int flags)
{
int ret = __get_any_page(page, pfn, flags);

if (ret == 1 && !PageHuge(page) && !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 (!PageLRU(page)) {
pr_info("soft_offline: %#lx: unknown non LRU page type %lx\n",
pfn, page->flags);
return -EIO;
}
}
return ret;
}

static int soft_offline_huge_page(struct page *page, int flags)
{
int ret;
unsigned long pfn = page_to_pfn(page);
struct page *hpage = compound_head(page);

/*
* This double-check of PageHWPoison is to avoid the race with
* memory_failure(). See also comment in __soft_offline_page().
*/
lock_page(hpage);
if (PageHWPoison(hpage)) {
unlock_page(hpage);
put_page(hpage);
pr_info("soft offline: %#lx hugepage already poisoned\n", pfn);
ret = -EBUSY;
goto out;
return -EBUSY;
}

ret = get_any_page(page, pfn, flags);
if (ret < 0)
goto out;
if (ret == 0)
goto done;
unlock_page(hpage);

/* Keep page count to indicate a given hugepage is isolated. */
ret = migrate_huge_page(hpage, new_page, MPOL_MF_MOVE_ALL, false,
Expand All @@ -1438,17 +1461,18 @@ static int soft_offline_huge_page(struct page *page, int flags)
if (ret) {
pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
pfn, ret, page->flags);
goto out;
} else {
set_page_hwpoison_huge_page(hpage);
dequeue_hwpoisoned_huge_page(hpage);
atomic_long_add(1 << compound_trans_order(hpage),
&num_poisoned_pages);
}
done:
/* keep elevated page count for bad page */
atomic_long_add(1 << compound_trans_order(hpage), &num_poisoned_pages);
set_page_hwpoison_huge_page(hpage);
dequeue_hwpoisoned_huge_page(hpage);
out:
return ret;
}

static int __soft_offline_page(struct page *page, int flags);

/**
* soft_offline_page - Soft offline a page.
* @page: page to offline
Expand Down Expand Up @@ -1477,62 +1501,60 @@ int soft_offline_page(struct page *page, int flags)
unsigned long pfn = page_to_pfn(page);
struct page *hpage = compound_trans_head(page);

if (PageHuge(page)) {
ret = soft_offline_huge_page(page, flags);
goto out;
if (PageHWPoison(page)) {
pr_info("soft offline: %#lx page already poisoned\n", pfn);
return -EBUSY;
}
if (PageTransHuge(hpage)) {
if (!PageHuge(page) && PageTransHuge(hpage)) {
if (PageAnon(hpage) && unlikely(split_huge_page(hpage))) {
pr_info("soft offline: %#lx: failed to split THP\n",
pfn);
ret = -EBUSY;
goto out;
return -EBUSY;
}
}

if (PageHWPoison(page)) {
pr_info("soft offline: %#lx page already poisoned\n", pfn);
ret = -EBUSY;
goto out;
}

ret = get_any_page(page, pfn, flags);
if (ret < 0)
goto out;
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)
goto out;
if (ret == 0)
goto done;
}
if (!PageLRU(page)) {
pr_info("soft_offline: %#lx: unknown non LRU page type %lx\n",
pfn, page->flags);
ret = -EIO;
goto out;
return ret;
if (ret) { /* for in-use pages */
if (PageHuge(page))
ret = soft_offline_huge_page(page, flags);
else
ret = __soft_offline_page(page, flags);
} else { /* for free pages */
if (PageHuge(page)) {
set_page_hwpoison_huge_page(hpage);
dequeue_hwpoisoned_huge_page(hpage);
atomic_long_add(1 << compound_trans_order(hpage),
&num_poisoned_pages);
} else {
SetPageHWPoison(page);
atomic_long_inc(&num_poisoned_pages);
}
}
/* keep elevated page count for bad page */
return ret;
}

static int __soft_offline_page(struct page *page, int flags)
{
int ret;
unsigned long pfn = page_to_pfn(page);

/*
* Synchronized using the page lock with memory_failure()
* Check PageHWPoison again inside page lock because PageHWPoison
* is set by memory_failure() outside page lock. Note that
* memory_failure() also double-checks PageHWPoison inside page lock,
* so there's no race between soft_offline_page() and memory_failure().
*/
lock_page(page);
wait_on_page_writeback(page);
if (PageHWPoison(page)) {
unlock_page(page);
put_page(page);
pr_info("soft offline: %#lx page already poisoned\n", pfn);
return -EBUSY;
}
/*
* Try to invalidate first. This should work for
* non dirty unmapped page cache pages.
Expand All @@ -1545,9 +1567,10 @@ int soft_offline_page(struct page *page, int flags)
*/
if (ret == 1) {
put_page(page);
ret = 0;
pr_info("soft_offline: %#lx: invalidated\n", pfn);
goto done;
SetPageHWPoison(page);
atomic_long_inc(&num_poisoned_pages);
return 0;
}

/*
Expand Down Expand Up @@ -1575,18 +1598,13 @@ int soft_offline_page(struct page *page, int flags)
pfn, ret, page->flags);
if (ret > 0)
ret = -EIO;
} else {
SetPageHWPoison(page);
atomic_long_inc(&num_poisoned_pages);
}
} else {
pr_info("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n",
pfn, ret, page_count(page), page->flags);
}
if (ret)
goto out;

done:
/* keep elevated page count for bad page */
atomic_long_inc(&num_poisoned_pages);
SetPageHWPoison(page);
out:
return ret;
}

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