linux-kernel - [RFC PATCH] mm: mincore: use PAGE_SIZE instead of PAGE_CACHE

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Date:	Wed, 12 Nov 2014 17:50:37 +0800
From:	Weijie Yang <weijie.yang@...sung.com>
To:	'Johannes Weiner' <hannes@...xchg.org>
Cc:	'Andrew Morton' <akpm@...ux-foundation.org>, mgorman@...e.de,
	'Rik van Riel' <riel@...hat.com>,
	'Weijie Yang' <weijie.yang.kh@...il.com>,
	'Linux-MM' <linux-mm@...ck.org>,
	'linux-kernel' <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH] mm: mincore: use PAGE_SIZE instead of PAGE_CACHE_SIZE

This is a RFC patch, because current PAGE_SIZE is equal to PAGE_CACHE_SIZE,
there isn't any difference and issue when running.

However, the current code mixes these two aligned_size inconsistently, and if
they are not equal in future mincore_unmapped_range() would check more file
pages than wanted.

According to man-page, mincore uses PAGE_SIZE as its size unit, so this patch
uses PAGE_SIZE instead of PAGE_CACHE_SIZE.

Signed-off-by: Weijie Yang <weijie.yang@...sung.com>
---
 mm/mincore.c |   19 +++++++++++++------
 1 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/mm/mincore.c b/mm/mincore.c
index 725c809..8c19bce 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -102,11 +102,18 @@ static void mincore_unmapped_range(struct vm_area_struct *vma,
 	int i;
 
 	if (vma->vm_file) {
-		pgoff_t pgoff;
+		pgoff_t pgoff, pgoff_end;
+		int j, count;
+		unsigned char res;
 
+		count = 1 << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
 		pgoff = linear_page_index(vma, addr);
-		for (i = 0; i < nr; i++, pgoff++)
-			vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
+		pgoff_end = linear_page_index(vma, end);
+		for (i = 0; pgoff < pgoff_end; pgoff++) {
+			res = mincore_page(vma->vm_file->f_mapping, pgoff);
+			for (j = 0; j < count; j++)
+				vec[i++] = res;
+		}
 	} else {
 		for (i = 0; i < nr; i++)
 			vec[i] = 0;
@@ -258,7 +265,7 @@ static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *v
  * return values:
  *  zero    - success
  *  -EFAULT - vec points to an illegal address
- *  -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE
+ *  -EINVAL - addr is not a multiple of PAGE_SIZE
  *  -ENOMEM - Addresses in the range [addr, addr + len] are
  *		invalid for the address space of this process, or
  *		specify one or more pages which are not currently
@@ -273,14 +280,14 @@ SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
 	unsigned char *tmp;
 
 	/* Check the start address: needs to be page-aligned.. */
- 	if (start & ~PAGE_CACHE_MASK)
+	if (start & ~PAGE_MASK)
 		return -EINVAL;
 
 	/* ..and we need to be passed a valid user-space range */
 	if (!access_ok(VERIFY_READ, (void __user *) start, len))
 		return -ENOMEM;
 
-	/* This also avoids any overflows on PAGE_CACHE_ALIGN */
+	/* This also avoids any overflows on PAGE_ALIGN */
 	pages = len >> PAGE_SHIFT;
 	pages += (len & ~PAGE_MASK) != 0;
 
-- 
1.7.0.4


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