linux-kernel - [PATCH] mm, thp: fix locking inconsistency in collapse_huge

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Date:	Fri,  3 Jun 2016 15:28:04 +0300
From:	Ebru Akagunduz <ebru.akagunduz@...il.com>
To:	akpm@...ux-foundation.org
Cc:	vbabka@...e.cz, sergey.senozhatsky.work@...il.com,
	mhocko@...nel.org, kirill.shutemov@...ux.intel.com,
	sfr@...b.auug.org.au, linux-mm@...ck.org,
	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
	riel@...hat.com, aarcange@...hat.com,
	Ebru Akagunduz <ebru.akagunduz@...il.com>
Subject: [PATCH] mm, thp: fix locking inconsistency in collapse_huge_page

After creating revalidate vma function, locking inconsistency occured
due to directing the code path to wrong label. This patch directs
to correct label and fix the inconsistency.

Related commit that caused inconsistency:
http://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/?id=da4360877094368f6dfe75bbe804b0f0a5d575b0

Signed-off-by: Ebru Akagunduz <ebru.akagunduz@...il.com>
---
 mm/huge_memory.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 292cedd..8043d91 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2493,13 +2493,18 @@ static void collapse_huge_page(struct mm_struct *mm,
 	curr_allocstall = sum_vm_event(ALLOCSTALL);
 	down_read(&mm->mmap_sem);
 	result = hugepage_vma_revalidate(mm, vma, address);
-	if (result)
-		goto out;
+	if (result) {
+		mem_cgroup_cancel_charge(new_page, memcg, true);
+		up_read(&mm->mmap_sem);
+		goto out_nolock;
+	}
 
 	pmd = mm_find_pmd(mm, address);
 	if (!pmd) {
 		result = SCAN_PMD_NULL;
-		goto out;
+		mem_cgroup_cancel_charge(new_page, memcg, true);
+		up_read(&mm->mmap_sem);
+		goto out_nolock;
 	}
 
 	/*
@@ -2513,8 +2518,9 @@ static void collapse_huge_page(struct mm_struct *mm,
 		 * label out. Continuing to collapse causes inconsistency.
 		 */
 		if (!__collapse_huge_page_swapin(mm, vma, address, pmd)) {
+			mem_cgroup_cancel_charge(new_page, memcg, true);
 			up_read(&mm->mmap_sem);
-			goto out;
+			goto out_nolock;
 		}
 	}
 
-- 
1.9.1