linux-kernel - [PATCH] mm: revert mremap pud

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Message-ID: <alpine.LNX.2.00.1310150330350.9078@eggly.anvils>
Date:	Tue, 15 Oct 2013 03:34:55 -0700 (PDT)
From:	Hugh Dickins <hughd@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Chen Gang <gang.chen@...anux.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [PATCH] mm: revert mremap pud_free anti-fix

Revert 1ecfd533f4c5 ("mm/mremap.c: call pud_free() after fail calling
pmd_alloc()").  The original code was correct: pud_alloc(), pmd_alloc(),
pte_alloc_map() ensure that the pud, pmd, pt is already allocated, and
seldom do they need to allocate; on failure, upper levels are freed if
appropriate by the subsequent do_munmap().  Whereas 1ecfd533f4c5 did an
unconditional pud_free() of a most-likely still-in-use pud: saved only
by the near-impossiblity of pmd_alloc() failing.

Signed-off-by: Hugh Dickins <hughd@...gle.com>
---

 mm/mremap.c |    5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

--- 3.12-rc5/mm/mremap.c	2013-09-16 17:37:56.841072270 -0700
+++ linux/mm/mremap.c	2013-10-15 03:07:09.140091599 -0700
@@ -25,7 +25,6 @@
 #include <asm/uaccess.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
-#include <asm/pgalloc.h>
 
 #include "internal.h"
 
@@ -63,10 +62,8 @@ static pmd_t *alloc_new_pmd(struct mm_st
 		return NULL;
 
 	pmd = pmd_alloc(mm, pud, addr);
-	if (!pmd) {
-		pud_free(mm, pud);
+	if (!pmd)
 		return NULL;
-	}
 
 	VM_BUG_ON(pmd_trans_huge(*pmd));
 
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