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Re: [dm-devel] [PATCH] Fix persistant mirror reactivation



On Thu, Apr 15, 2004 at 01:40:27PM -0500, AJ Lewis wrote:
> The attached patch against 2.6.5-udm4 fixes persistant mirror reactivation:
>   - count_bits() fxn was broken.  It went into an infinite loop because n
>     was
>     never incremented.
>   - the size parameter passed into the find_*_bit fxns from count_bits() was
>     also wrong - it needs to be in bits, not bytes.

Alasdair pointed me at the hweight* fxns - the attached patch is a
replacement patch for the previous one I posted to use this to (hopefully)
do the same thing more efficiently.  So apply this instead of my previous
patch.

Regards,
-- 
AJ Lewis                                   Voice:  612-638-0500
Red Hat Inc.                               E-Mail: alewis redhat com
720 Washington Ave. SE, Suite 200
Minneapolis, MN 55414

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Exchange slow bit-by-bit count to use hweight32 to count bits per uint32_t
--- diff/drivers/md/dm-log.c	2004-04-15 14:51:20.625892881 -0500
+++ source/drivers/md/dm-log.c	2004-04-15 14:48:12.293747603 -0500
@@ -424,25 +424,14 @@
 	core_dtr(log);
 }
 
-static int count_bits(unsigned long *addr, unsigned size)
+static int count_bits32(uint32_t *addr, unsigned size)
 {
-	/* FIXME: test this */
-#if 1
-	int n, count = 0;
+	int count = 0, i;
 
-	n = find_first_bit(addr, size);
-	while (n < size) {
-		count++;
-		find_next_bit(addr, size, n + 1);
+	for (i = 0; i < size; i++) {
+		count += hweight32(*(addr+i));
 	}
-
-	return count;
-#else
-	int count = 0;
-        for (i = 0; i < lc->region_count; i++)
-                count += log_test_bit(lc->sync_bits, i);
 	return count;
-#endif
 }
 
 static int disk_resume(struct dirty_log *log)
@@ -469,7 +458,7 @@
 
 	/* copy clean across to sync */
 	memcpy(lc->sync_bits, lc->clean_bits, size);
-	lc->sync_count = count_bits((unsigned long *) lc->clean_bits, size);
+	lc->sync_count = count_bits32(lc->clean_bits, lc->bitset_uint32_count);
 
 	/* write the bits */
 	r = write_bits(lc);

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