linux-kernel - [PATCH] raid6: fix the input of raid6 algorithm

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Date:   Tue, 23 Aug 2016 11:22:57 +0800
From:   liuzhengyuan@...inos.cn
To:     hpa@...or.com
Cc:     shli@...nel.org, linux-raid@...r.kernel.org, fenghua.yu@...el.com,
        linux-kernel@...r.kernel.org, liuzhengyuang521@...il.com,
        ZhengYuan Liu <liuzhengyuan@...inos.cn>
Subject: [PATCH] raid6: fix the input of raid6 algorithm

From: ZhengYuan Liu <liuzhengyuan@...inos.cn>

To test and choose an best algorithm for raid6, disk number
and disk data must be offered. Those input depend on page
size and gfmul table at current time. It would lead the disk
number less than 4 when the page size is more than 64KB.This
patch would support arbitrarily page size by defining a macro
for disk number and using random number to fill with disk data.

Signed-off-by: ZhengYuan Liu <liuzhengyuan@...inos.cn>
---
 lib/raid6/algos.c | 36 ++++++++++++++++++++++--------------
 1 file changed, 22 insertions(+), 14 deletions(-)

diff --git a/lib/raid6/algos.c b/lib/raid6/algos.c
index 975c6e0..f15a4d2 100644
--- a/lib/raid6/algos.c
+++ b/lib/raid6/algos.c
@@ -23,6 +23,7 @@
 #else
 #include <linux/module.h>
 #include <linux/gfp.h>
+#include <linux/random.h>
 #if !RAID6_USE_EMPTY_ZERO_PAGE
 /* In .bss so it's zeroed */
 const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
@@ -30,6 +31,8 @@ EXPORT_SYMBOL(raid6_empty_zero_page);
 #endif
 #endif
 
+#define RAID6_DISKS	8
+
 struct raid6_calls raid6_call;
 EXPORT_SYMBOL_GPL(raid6_call);
 
@@ -129,7 +132,7 @@ static inline const struct raid6_recov_calls *raid6_choose_recov(void)
 }
 
 static inline const struct raid6_calls *raid6_choose_gen(
-	void *(*const dptrs)[(65536/PAGE_SIZE)+2], const int disks)
+	void *(*const dptrs)[RAID6_DISKS], const int disks)
 {
 	unsigned long perf, bestgenperf, bestxorperf, j0, j1;
 	int start = (disks>>1)-1, stop = disks-3;	/* work on the second half of the disks */
@@ -206,27 +209,32 @@ static inline const struct raid6_calls *raid6_choose_gen(
 
 int __init raid6_select_algo(void)
 {
-	const int disks = (65536/PAGE_SIZE)+2;
+	const int disks = RAID6_DISKS;
 
 	const struct raid6_calls *gen_best;
 	const struct raid6_recov_calls *rec_best;
-	char *syndromes;
-	void *dptrs[(65536/PAGE_SIZE)+2];
-	int i;
-
-	for (i = 0; i < disks-2; i++)
-		dptrs[i] = ((char *)raid6_gfmul) + PAGE_SIZE*i;
+	char *disk_ptr;
+	void *dptrs[RAID6_DISKS];
+	int i, j;
 
-	/* Normal code - use a 2-page allocation to avoid D$ conflict */
-	syndromes = (void *) __get_free_pages(GFP_KERNEL, 1);
+	/* use a 8-page allocation, The first 6 pages for disks
+	   and the last 2 pages for syndromes */
+	disk_ptr = (void *) __get_free_pages(GFP_KERNEL, 3);
 
-	if (!syndromes) {
+	if (!disk_ptr) {
 		pr_err("raid6: Yikes!  No memory available.\n");
 		return -ENOMEM;
 	}
 
-	dptrs[disks-2] = syndromes;
-	dptrs[disks-1] = syndromes + PAGE_SIZE;
+	/* Fix-me: may should use get_random_bytes_arch() instead of get_random_bytes() */
+	for (i = 0; i < disks-2; i++) {
+		dptrs[i] = disk_ptr + PAGE_SIZE*i;
+		for (j = 0; j < PAGE_SIZE; j++)
+			get_random_bytes(dptrs[i]+j, 1);
+	}
+
+	dptrs[disks-2] = disk_ptr + PAGE_SIZE*(disks-2);
+	dptrs[disks-1] = disk_ptr + PAGE_SIZE*(disks-1);
 
 	/* select raid gen_syndrome function */
 	gen_best = raid6_choose_gen(&dptrs, disks);
@@ -234,7 +242,7 @@ int __init raid6_select_algo(void)
 	/* select raid recover functions */
 	rec_best = raid6_choose_recov();
 
-	free_pages((unsigned long)syndromes, 1);
+	free_pages((unsigned long)disk_ptr, 3);
 
 	return gen_best && rec_best ? 0 : -EINVAL;
 }
-- 
1.9.1