lib/raid6: cleanup gen_syndrome function selection

Reorders functions in raid6_algos as well as the preference check
to reduce the number of functions tested on initialization.

Also, creates symmetry between choosing the gen_syndrome functions
and choosing the recovery functions.

Signed-off-by: Jim Kukunas <james.t.kukunas@linux.intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 57 insertions, 47 deletions

diff --git a/lib/raid6/algos.c b/lib/raid6/algos.c
index 5a7f8022be13..589f5f50ad2e 100644
--- a/lib/raid6/algos.c
+++ b/lib/raid6/algos.c
@@ -34,10 +34,6 @@ struct raid6_calls raid6_call;
 EXPORT_SYMBOL_GPL(raid6_call);
 
 const struct raid6_calls * const raid6_algos[] = {
-        &raid6_intx1,
-        &raid6_intx2,
-        &raid6_intx4,
-        &raid6_intx8,
 #if defined(__ia64__)
         &raid6_intx16,
         &raid6_intx32,
@@ -61,6 +57,10 @@ const struct raid6_calls * const raid6_algos[] = {
         &raid6_altivec4,
         &raid6_altivec8,
 #endif
+        &raid6_intx1,
+        &raid6_intx2,
+        &raid6_intx4,
+        &raid6_intx8,
         NULL
 };
 
@@ -86,7 +86,7 @@ const struct raid6_recov_calls *const raid6_recov_algos[] = {
 #define time_before(x, y) ((x) < (y))
 #endif
 
-static inline void raid6_choose_recov(void)
+static inline const struct raid6_recov_calls *raid6_choose_recov(void)
 {
         const struct raid6_recov_calls *const *algo;
         const struct raid6_recov_calls *best;
@@ -103,62 +103,38 @@ static inline void raid6_choose_recov(void)
                 printk("raid6: using %s recovery algorithm\n", best->name);
         } else
                 printk("raid6: Yikes! No recovery algorithm found!\n");
-}
-
 
-/* Try to pick the best algorithm */
-/* This code uses the gfmul table as convenient data set to abuse */
+        return best;
+}
 
-int __init raid6_select_algo(void)
+static inline const struct raid6_calls *raid6_choose_gen(
+        void *(*const dptrs)[(65536/PAGE_SIZE)+2], const int disks)
 {
-        const struct raid6_calls * const * algo;
-        const struct raid6_calls * best;
-        char *syndromes;
-        void *dptrs[(65536/PAGE_SIZE)+2];
-        int i, disks;
-        unsigned long perf, bestperf;
-        int bestprefer;
-        unsigned long j0, j1;
-
-        disks = (65536/PAGE_SIZE)+2;
-        for ( i = 0 ; i < disks-2 ; i++ ) {
-                dptrs[i] = ((char *)raid6_gfmul) + PAGE_SIZE*i;
-        }
-
-        /* Normal code - use a 2-page allocation to avoid D$ conflict */
-        syndromes = (void *) __get_free_pages(GFP_KERNEL, 1);
-
-        if ( !syndromes ) {
-                printk("raid6: Yikes!  No memory available.\n");
-                return -ENOMEM;
-        }
-
-        dptrs[disks-2] = syndromes;
-        dptrs[disks-1] = syndromes + PAGE_SIZE;
+        unsigned long perf, bestperf, j0, j1;
+        const struct raid6_calls *const *algo;
+        const struct raid6_calls *best;
 
-        bestperf = 0;  bestprefer = 0;  best = NULL;
+        for (bestperf = 0, best = NULL, algo = raid6_algos; *algo; algo++) {
+                if (!best || (*algo)->prefer >= best->prefer) {
+                        if ((*algo)->valid && !(*algo)->valid())
+                                continue;
 
-        for ( algo = raid6_algos ; *algo ; algo++ ) {
-                if ( !(*algo)->valid || (*algo)->valid() ) {
                         perf = 0;
 
                         preempt_disable();
                         j0 = jiffies;
-                        while ( (j1 = jiffies) == j0 )
+                        while ((j1 = jiffies) == j0)
                                 cpu_relax();
                         while (time_before(jiffies,
                                             j1 + (1<<RAID6_TIME_JIFFIES_LG2))) {
-                                (*algo)->gen_syndrome(disks, PAGE_SIZE, dptrs);
+                                (*algo)->gen_syndrome(disks, PAGE_SIZE, *dptrs);
                                 perf++;
                         }
                         preempt_enable();
 
-                        if ( (*algo)->prefer > bestprefer ||
-                             ((*algo)->prefer == bestprefer &&
-                              perf > bestperf) ) {
-                                best = *algo;
-                                bestprefer = best->prefer;
+                        if (perf > bestperf) {
                                 bestperf = perf;
+                                best = *algo;
                         }
                         printk("raid6: %-8s %5ld MB/s\n", (*algo)->name,
                                (perf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
@@ -173,12 +149,46 @@ int __init raid6_select_algo(void)
         } else
                 printk("raid6: Yikes!  No algorithm found!\n");
 
-        free_pages((unsigned long)syndromes, 1);
+        return best;
+}
+
+
+/* Try to pick the best algorithm */
+/* This code uses the gfmul table as convenient data set to abuse */
+
+int __init raid6_select_algo(void)
+{
+        const int disks = (65536/PAGE_SIZE)+2;
+
+        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;
+
+        /* Normal code - use a 2-page allocation to avoid D$ conflict */
+        syndromes = (void *) __get_free_pages(GFP_KERNEL, 1);
+
+        if (!syndromes) {
+                printk("raid6: Yikes!  No memory available.\n");
+                return -ENOMEM;
+        }
+
+        dptrs[disks-2] = syndromes;
+        dptrs[disks-1] = syndromes + PAGE_SIZE;
+
+        /* select raid gen_syndrome function */
+        gen_best = raid6_choose_gen(&dptrs, disks);
 
         /* select raid recover functions */
-        raid6_choose_recov();
+        rec_best = raid6_choose_recov();
+
+        free_pages((unsigned long)syndromes, 1);
 
-        return best ? 0 : -EINVAL;
+        return gen_best && rec_best ? 0 : -EINVAL;
 }
 
 static void raid6_exit(void)