linux-kernel - [PATCH 1/2] mm/thp/pagecache: Only withdraw page table after a successful deposit

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Date:   Mon, 12 Dec 2016 22:04:27 +0530
From:   "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:     akpm@...ux-foundation.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        mpe@...erman.id.au
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: [PATCH 1/2] mm/thp/pagecache: Only withdraw page table after a successful deposit

The current code wrongly called withdraw in the error path. But we
haven't depoisted the page table yet in the only error path in that
function. So for now remove that withdraw completely. If we take
that "out:" branch, we should have vmf->prealloc_pte already pointing
to the allocated page table.

Fixes: "mm: THP page cache support for ppc64"

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
---
 mm/memory.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 455c3e628d52..36c774f9259e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3008,13 +3008,6 @@ static int do_set_pmd(struct vm_fault *vmf, struct page *page)
 	ret = 0;
 	count_vm_event(THP_FILE_MAPPED);
 out:
-	/*
-	 * If we are going to fallback to pte mapping, do a
-	 * withdraw with pmd lock held.
-	 */
-	if (arch_needs_pgtable_deposit() && ret == VM_FAULT_FALLBACK)
-		vmf->prealloc_pte = pgtable_trans_huge_withdraw(vma->vm_mm,
-								vmf->pmd);
 	spin_unlock(vmf->ptl);
 	return ret;
 }
-- 
2.10.2