linux-kernel - [PATCH 1/6] mm: use mm_struct to resolve gate vma's in __get_user

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Message-Id: <1299631343-4499-2-git-send-email-wilsons@start.ca>
Date:	Tue,  8 Mar 2011 19:42:18 -0500
From:	Stephen Wilson <wilsons@...rt.ca>
To:	linux-mm@...ck.org
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Rik van Riel <riel@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Roland McGrath <roland@...hat.com>,
	Matt Mackall <mpm@...enic.com>,
	David Rientjes <rientjes@...gle.com>,
	Nick Piggin <npiggin@...nel.dk>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Mel Gorman <mel@....ul.ie>, Ingo Molnar <mingo@...e.hu>,
	Michel Lespinasse <walken@...gle.com>,
	Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org,
	Stephen Wilson <wilsons@...rt.ca>
Subject: [PATCH 1/6] mm: use mm_struct to resolve gate vma's in __get_user_pages

We now check if a requested user page overlaps a gate vma using the supplied mm
instead of the supplied task.  The given task is now used solely for accounting
purposes and may be NULL.

Signed-off-by: Stephen Wilson <wilsons@...rt.ca>
---
 mm/memory.c |   18 +++++++++++-------
 1 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 3863e86..36445e3 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1437,9 +1437,9 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 		struct vm_area_struct *vma;
 
 		vma = find_extend_vma(mm, start);
-		if (!vma && in_gate_area(tsk->mm, start)) {
+		if (!vma && in_gate_area(mm, start)) {
 			unsigned long pg = start & PAGE_MASK;
-			struct vm_area_struct *gate_vma = get_gate_vma(tsk->mm);
+			struct vm_area_struct *gate_vma = get_gate_vma(mm);
 			pgd_t *pgd;
 			pud_t *pud;
 			pmd_t *pmd;
@@ -1533,10 +1533,13 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 						return i ? i : -EFAULT;
 					BUG();
 				}
-				if (ret & VM_FAULT_MAJOR)
-					tsk->maj_flt++;
-				else
-					tsk->min_flt++;
+
+				if (tsk) {
+					if (ret & VM_FAULT_MAJOR)
+						tsk->maj_flt++;
+					else
+						tsk->min_flt++;
+				}
 
 				if (ret & VM_FAULT_RETRY) {
 					*nonblocking = 0;
@@ -1581,7 +1584,8 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 
 /**
  * get_user_pages() - pin user pages in memory
- * @tsk:	task_struct of target task
+ * @tsk:	the task_struct to use for page fault accounting, or
+ *		NULL if faults are not to be recorded.
  * @mm:		mm_struct of target mm
  * @start:	starting user address
  * @nr_pages:	number of pages from start to pin
-- 
1.7.3.5

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