linux-kernel - [PATCHv9-rebased 27/32] khugepaged: move up_read(mmap_sem) out of khugepaged_alloc

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Message-Id: <1465297246-98985-28-git-send-email-kirill.shutemov@linux.intel.com>
Date:	Tue,  7 Jun 2016 14:00:41 +0300
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Hugh Dickins <hughd@...gle.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Dave Hansen <dave.hansen@...el.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Christoph Lameter <cl@...two.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Jerome Marchand <jmarchan@...hat.com>,
	Yang Shi <yang.shi@...aro.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	Andres Lagar-Cavilla <andreslc@...gle.com>,
	Ning Qu <quning@...il.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCHv9-rebased 27/32] khugepaged: move up_read(mmap_sem) out of khugepaged_alloc_page()

Both variants of khugepaged_alloc_page() do up_read(&mm->mmap_sem)
first: no point keep it inside the function.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 mm/khugepaged.c | 25 ++++++++++---------------
 1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 1b08a5c57140..84c2bf01ae42 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -746,19 +746,10 @@ static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
 }
 
 static struct page *
-khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
-		       unsigned long address, int node)
+khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
 {
 	VM_BUG_ON_PAGE(*hpage, *hpage);
 
-	/*
-	 * Before allocating the hugepage, release the mmap_sem read lock.
-	 * The allocation can take potentially a long time if it involves
-	 * sync compaction, and we do not need to hold the mmap_sem during
-	 * that. We will recheck the vma after taking it again in write mode.
-	 */
-	up_read(&mm->mmap_sem);
-
 	*hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
 	if (unlikely(!*hpage)) {
 		count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
@@ -819,10 +810,8 @@ static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
 }
 
 static struct page *
-khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
-		       unsigned long address, int node)
+khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
 {
-	up_read(&mm->mmap_sem);
 	VM_BUG_ON(!*hpage);
 
 	return  *hpage;
@@ -941,8 +930,14 @@ static void collapse_huge_page(struct mm_struct *mm,
 	/* Only allocate from the target node */
 	gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE | __GFP_THISNODE;
 
-	/* release the mmap_sem read lock. */
-	new_page = khugepaged_alloc_page(hpage, gfp, mm, address, node);
+	/*
+	 * Before allocating the hugepage, release the mmap_sem read lock.
+	 * The allocation can take potentially a long time if it involves
+	 * sync compaction, and we do not need to hold the mmap_sem during
+	 * that. We will recheck the vma after taking it again in write mode.
+	 */
+	up_read(&mm->mmap_sem);
+	new_page = khugepaged_alloc_page(hpage, gfp, node);
 	if (!new_page) {
 		result = SCAN_ALLOC_HUGE_PAGE_FAIL;
 		goto out_nolock;
-- 
2.8.1