linux-kernel - [ 86/89] mm: soft offline: split thp at the beginning of soft_offline

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Message-Id: <20121203143159.879481717@decadent.org.uk>
Date:	Mon, 03 Dec 2012 14:33:12 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Andi Kleen <andi@...stfloor.org>,
	Tony Luck <tony.luck@...el.com>,
	Andi Kleen <andi.kleen@...el.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [ 86/89] mm: soft offline: split thp at the beginning of soft_offline_page()

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Naoya Horiguchi <n-horiguchi@...jp.nec.com>

commit 783657a7dc20e5c0efbc9a09a9dd38e238a723da upstream.

When we try to soft-offline a thp tail page, put_page() is called on the
tail page unthinkingly and VM_BUG_ON is triggered in put_compound_page().

This patch splits thp before going into the main body of soft-offlining.

Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc: Andi Kleen <andi@...stfloor.org>
Cc: Tony Luck <tony.luck@...el.com>
Cc: Andi Kleen <andi.kleen@...el.com>
Cc: Wu Fengguang <fengguang.wu@...el.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 mm/memory-failure.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 6c5899b..8b20278 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1476,9 +1476,17 @@ int soft_offline_page(struct page *page, int flags)
 {
 	int ret;
 	unsigned long pfn = page_to_pfn(page);
+	struct page *hpage = compound_trans_head(page);
 
 	if (PageHuge(page))
 		return soft_offline_huge_page(page, flags);
+	if (PageTransHuge(hpage)) {
+		if (PageAnon(hpage) && unlikely(split_huge_page(hpage))) {
+			pr_info("soft offline: %#lx: failed to split THP\n",
+				pfn);
+			return -EBUSY;
+		}
+	}
 
 	ret = get_any_page(page, pfn, flags);
 	if (ret < 0)


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