packages: lvm2/lvm2-no-floor.patch (NEW) - NEW; integer-only replacement fo...

[sparky]

Author: sparky                       Date: Fri Jul 30 17:00:26 2010 GMT
Module: packages                      Tag: HEAD
---- Log message:
- NEW; integer-only replacement for floor( rand( ) / N )

---- Files affected:
packages/lvm2:
   lvm2-no-floor.patch (NONE -> 1.1)  (NEW)

---- Diffs:

================================================================
Index: packages/lvm2/lvm2-no-floor.patch
diff -u /dev/null packages/lvm2/lvm2-no-floor.patch:1.1
--- /dev/null	Fri Jul 30 19:00:26 2010
+++ packages/lvm2/lvm2-no-floor.patch	Fri Jul 30 19:00:21 2010
@@ -0,0 +1,69 @@
+From ab3a151bdae8566fddbd91cdc86c600083890f59 Mon Sep 17 00:00:00 2001
+From: Przemyslaw Iskra <sparky at pld-linux.org>
+Date: Fri, 30 Jul 2010 18:45:43 +0200
+Subject: [PATCH] Don't use floor() in _bitset_with_random_bits
+
+Use _even_rand() function instead of floor() in
+_bitset_with_random_bits(). floor() function is missing in dietlibc (on
+architectures other than x86). Moreover using floor() to clip rand
+results does not assure even result distribution.
+_even_rand() uses integer arithmetic only and is designed to return evenly
+distributed results.
+
+Signed-off-by: Przemyslaw Iskra <sparky at pld-linux.org>
+---
+ configure.in            |    3 +--
+ lib/metadata/metadata.c |   16 +++++++++++++++-
+ 2 files changed, 16 insertions(+), 3 deletions(-)
+
+diff --git a/configure.in b/configure.in
+index bd56136..6f6c67e 100644
+--- a/configure.in
++++ b/configure.in
+@@ -125,8 +125,7 @@ AC_STRUCT_TM
+ 
+ ################################################################################
+ dnl -- Check for functions
+-AC_SEARCH_LIBS([floor], [m], , [AC_MSG_ERROR(bailing out)])
+-AC_CHECK_FUNCS([floor ftruncate gethostname getpagesize \
++AC_CHECK_FUNCS([ftruncate gethostname getpagesize \
+   gettimeofday memset mkdir mkfifo rmdir munmap nl_langinfo setenv setlocale \
+   strcasecmp strchr strcspn strspn strdup strncasecmp strerror strrchr \
+   strstr strtol strtoul uname], , [AC_MSG_ERROR(bailing out)])
+diff --git a/lib/metadata/metadata.c b/lib/metadata/metadata.c
+index 07222a7..6ee7731 100644
+--- a/lib/metadata/metadata.c
++++ b/lib/metadata/metadata.c
+@@ -1018,6 +1018,20 @@ static int _recalc_extents(uint32_t *extents, const char *desc1,
+ 	return 1;
+ }
+ 
++/* return random integer in [0,max) interval */
++static unsigned _even_rand( unsigned *seed, unsigned max )
++{
++	unsigned r, ret;
++
++	/* make sure distribution is even */
++	do {
++		r = (unsigned) rand_r( seed );
++		ret = r % max;
++	} while ( r - ret >= RAND_MAX - max );
++
++	return ret;
++}
++
+ static dm_bitset_t _bitset_with_random_bits(struct dm_pool *mem, uint32_t num_bits,
+ 					    uint32_t num_set_bits, unsigned *seed)
+ {
+@@ -1040,7 +1054,7 @@ static dm_bitset_t _bitset_with_random_bits(struct dm_pool *mem, uint32_t num_bi
+ 	/* Perform loop num_set_bits times, selecting one bit each time */
+ 	while (i++ < num_bits) {
+ 		/* Select a random bit between 0 and (i-1) inclusive. */
+-		bit_selected = (unsigned) floor(i * (rand_r(seed) / (RAND_MAX + 1.0)));
++		bit_selected = _even_rand( seed, i );
+ 
+ 		/*
+ 		 * If the bit was already set, set the new bit that became
+-- 
+1.7.1
+
================================================================