Ocfs2 devel - Jun 2012 - [PATCH v2 01/10] string: introduce memweight

memweight() is the function that counts the total number of bits set
in memory area.  Unlike bitmap_weight(), memweight() takes pointer
and size in bytes to specify a memory area which does not need to be
aligned to long-word boundary.

Signed-off-by: Akinobu Mita <akinobu.mita at gmail.com>
Cc: Anders Larsen <al at alarsen.net>
Cc: Alasdair Kergon <agk at redhat.com>
Cc: dm-devel at redhat.com
Cc: linux-fsdevel at vger.kernel.org
Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
Cc: linux-media at vger.kernel.org
Cc: Mark Fasheh <mfasheh at suse.com>
Cc: Joel Becker <jlbec at evilplan.org>
Cc: ocfs2-devel at oss.oracle.com
Cc: Jan Kara <jack at suse.cz>
Cc: linux-ext4 at vger.kernel.org
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Andreas Dilger <adilger.kernel at dilger.ca>
Cc: "Theodore Ts'o" <tytso at mit.edu>
Cc: Matthew Wilcox <matthew at wil.cx>
---

v2: simplify memweight(), adviced by Jan Kara

 include/linux/string.h |    3 +++
 lib/string.c           |   32 ++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 0 deletions(-)

diff --git a/include/linux/string.h b/include/linux/string.h
index e033564..ffe0442 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -145,4 +145,7 @@ static inline bool strstarts(const char *str, const char
*prefix)
 	return strncmp(str, prefix, strlen(prefix)) == 0;
 }
 #endif
+
+extern size_t memweight(const void *ptr, size_t bytes);
+
 #endif /* _LINUX_STRING_H_ */
diff --git a/lib/string.c b/lib/string.c
index e5878de..bf4d5a8 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -26,6 +26,7 @@
 #include <linux/export.h>
 #include <linux/bug.h>
 #include <linux/errno.h>
+#include <linux/bitmap.h>
 
 #ifndef __HAVE_ARCH_STRNICMP
 /**
@@ -824,3 +825,34 @@ void *memchr_inv(const void *start, int c, size_t bytes)
 	return check_bytes8(start, value, bytes % 8);
 }
 EXPORT_SYMBOL(memchr_inv);
+
+/**
+ * memweight - count the total number of bits set in memory area
+ * @ptr: pointer to the start of the area
+ * @bytes: the size of the area
+ */
+size_t memweight(const void *ptr, size_t bytes)
+{
+	size_t w = 0;
+	size_t longs;
+	const unsigned char *bitmap = ptr;
+
+	for (; bytes > 0 && ((unsigned long)bitmap) % sizeof(long);
+			bytes--, bitmap++)
+		w += hweight8(*bitmap);
+
+	longs = bytes / sizeof(long);
+	if (longs) {
+		BUG_ON(longs >= INT_MAX / BITS_PER_LONG);
+		w += bitmap_weight((unsigned long *)bitmap,
+				longs * BITS_PER_LONG);
+		bytes -= longs * sizeof(long);
+		bitmap += longs * sizeof(long);
+	}
+
+	for (; bytes > 0; bytes--, bitmap++)
+		w += hweight8(*bitmap);
+
+	return w;
+}
+EXPORT_SYMBOL(memweight);
-- 
1.7.7.6

Use memweight to count the total number of bits set in memory area.

Signed-off-by: Akinobu Mita <akinobu.mita at gmail.com>
Cc: Mark Fasheh <mfasheh at suse.com>
Cc: Joel Becker <jlbec at evilplan.org>
Cc: ocfs2-devel at oss.oracle.com
---

No changes from v1

 fs/ocfs2/localalloc.c |    8 ++------
 1 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/fs/ocfs2/localalloc.c b/fs/ocfs2/localalloc.c
index 210c352..a9f78c7 100644
--- a/fs/ocfs2/localalloc.c
+++ b/fs/ocfs2/localalloc.c
@@ -784,14 +784,10 @@ bail:
 
 static u32 ocfs2_local_alloc_count_bits(struct ocfs2_dinode *alloc)
 {
-	int i;
-	u8 *buffer;
-	u32 count = 0;
+	u32 count;
 	struct ocfs2_local_alloc *la = OCFS2_LOCAL_ALLOC(alloc);
 
-	buffer = la->la_bitmap;
-	for (i = 0; i < le16_to_cpu(la->la_size); i++)
-		count += hweight8(buffer[i]);
+	count = memweight(la->la_bitmap, le16_to_cpu(la->la_size));
 
 	trace_ocfs2_local_alloc_count_bits(count);
 	return count;
-- 
1.7.7.6

2012/6/4 Jan Kara <jack at suse.cz>:
> On Sat 02-06-12 22:40:07, Akinobu Mita wrote:
>> memweight() is the function that counts the total number of bits set
>> in memory area. ?Unlike bitmap_weight(), memweight() takes pointer
>> and size in bytes to specify a memory area which does not need to be
>> aligned to long-word boundary.
>>
>> Signed-off-by: Akinobu Mita <akinobu.mita at gmail.com>
>> Cc: Anders Larsen <al at alarsen.net>
>> Cc: Alasdair Kergon <agk at redhat.com>
>> Cc: dm-devel at redhat.com
>> Cc: linux-fsdevel at vger.kernel.org
>> Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
>> Cc: linux-media at vger.kernel.org
>> Cc: Mark Fasheh <mfasheh at suse.com>
>> Cc: Joel Becker <jlbec at evilplan.org>
>> Cc: ocfs2-devel at oss.oracle.com
>> Cc: Jan Kara <jack at suse.cz>
>> Cc: linux-ext4 at vger.kernel.org
>> Cc: Andrew Morton <akpm at linux-foundation.org>
>> Cc: Andreas Dilger <adilger.kernel at dilger.ca>
>> Cc: "Theodore Ts'o" <tytso at mit.edu>
>> Cc: Matthew Wilcox <matthew at wil.cx>
>> ---
>>
>> v2: simplify memweight(), adviced by Jan Kara
>>
>> ?include/linux/string.h | ? ?3 +++
>> ?lib/string.c ? ? ? ? ? | ? 32 ++++++++++++++++++++++++++++++++
>> ?2 files changed, 35 insertions(+), 0 deletions(-)
>>
>> diff --git a/include/linux/string.h b/include/linux/string.h
>> index e033564..ffe0442 100644
>> --- a/include/linux/string.h
>> +++ b/include/linux/string.h
>> @@ -145,4 +145,7 @@ static inline bool strstarts(const char *str, const
char *prefix)
>> ? ? ? return strncmp(str, prefix, strlen(prefix)) == 0;
>> ?}
>> ?#endif
>> +
>> +extern size_t memweight(const void *ptr, size_t bytes);
>> +
>> ?#endif /* _LINUX_STRING_H_ */
>> diff --git a/lib/string.c b/lib/string.c
>> index e5878de..bf4d5a8 100644
>> --- a/lib/string.c
>> +++ b/lib/string.c
>> @@ -26,6 +26,7 @@
>> ?#include <linux/export.h>
>> ?#include <linux/bug.h>
>> ?#include <linux/errno.h>
>> +#include <linux/bitmap.h>
>>
>> ?#ifndef __HAVE_ARCH_STRNICMP
>> ?/**
>> @@ -824,3 +825,34 @@ void *memchr_inv(const void *start, int c, size_t
bytes)
>> ? ? ? return check_bytes8(start, value, bytes % 8);
>> ?}
>> ?EXPORT_SYMBOL(memchr_inv);
>> +
>> +/**
>> + * memweight - count the total number of bits set in memory area
>> + * @ptr: pointer to the start of the area
>> + * @bytes: the size of the area
>> + */
>> +size_t memweight(const void *ptr, size_t bytes)
>> +{
>> + ? ? size_t w = 0;
>> + ? ? size_t longs;
>> + ? ? const unsigned char *bitmap = ptr;
>> +
>> + ? ? for (; bytes > 0 && ((unsigned long)bitmap) %
sizeof(long);
>> + ? ? ? ? ? ? ? ? ? ? bytes--, bitmap++)
>> + ? ? ? ? ? ? w += hweight8(*bitmap);
>> +
>> + ? ? longs = bytes / sizeof(long);
>> + ? ? if (longs) {
>> + ? ? ? ? ? ? BUG_ON(longs >= INT_MAX / BITS_PER_LONG);
>> + ? ? ? ? ? ? w += bitmap_weight((unsigned long *)bitmap,
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? longs * BITS_PER_LONG);
>> + ? ? ? ? ? ? bytes -= longs * sizeof(long);
>> + ? ? ? ? ? ? bitmap += longs * sizeof(long);
>> + ? ? }
>> +
>> + ? ? for (; bytes > 0; bytes--, bitmap++)
>> + ? ? ? ? ? ? w += hweight8(*bitmap);
> ?Looking at bitmap_weight() it seems this last loop is not needed. Just
> pass to bitmap_weight() bytes*BITS_PER_BYTE. Also generally this function
> doesn't seem necessary at all at least for ext2 & ext3 (sorry for
not
> noticing this earlier...).
This last loop is necessary for big-endian architecture.
if bytes % sizeof(long) != 0, bitmap_weight() counts one-bits in wrong
byte-field
of the last long word.

2012/6/4 Jan Kara <jack at suse.cz>:
> On Mon 04-06-12 20:46:14, Akinobu Mita wrote:
>> 2012/6/4 Jan Kara <jack at suse.cz>:
>> > On Sat 02-06-12 22:40:07, Akinobu Mita wrote:
>> >> memweight() is the function that counts the total number of
bits set
>> >> in memory area. ?Unlike bitmap_weight(), memweight() takes
pointer
>> >> and size in bytes to specify a memory area which does not need
to be
>> >> aligned to long-word boundary.
>> >>
>> >> Signed-off-by: Akinobu Mita <akinobu.mita at gmail.com>
>> >> Cc: Anders Larsen <al at alarsen.net>
>> >> Cc: Alasdair Kergon <agk at redhat.com>
>> >> Cc: dm-devel at redhat.com
>> >> Cc: linux-fsdevel at vger.kernel.org
>> >> Cc: Laurent Pinchart <laurent.pinchart at
ideasonboard.com>
>> >> Cc: linux-media at vger.kernel.org
>> >> Cc: Mark Fasheh <mfasheh at suse.com>
>> >> Cc: Joel Becker <jlbec at evilplan.org>
>> >> Cc: ocfs2-devel at oss.oracle.com
>> >> Cc: Jan Kara <jack at suse.cz>
>> >> Cc: linux-ext4 at vger.kernel.org
>> >> Cc: Andrew Morton <akpm at linux-foundation.org>
>> >> Cc: Andreas Dilger <adilger.kernel at dilger.ca>
>> >> Cc: "Theodore Ts'o" <tytso at mit.edu>
>> >> Cc: Matthew Wilcox <matthew at wil.cx>
>> >> ---
>> >>
>> >> v2: simplify memweight(), adviced by Jan Kara
>> >>
>> >> ?include/linux/string.h | ? ?3 +++
>> >> ?lib/string.c ? ? ? ? ? | ? 32
++++++++++++++++++++++++++++++++
>> >> ?2 files changed, 35 insertions(+), 0 deletions(-)
>> >>
>> >> diff --git a/include/linux/string.h b/include/linux/string.h
>> >> index e033564..ffe0442 100644
>> >> --- a/include/linux/string.h
>> >> +++ b/include/linux/string.h
>> >> @@ -145,4 +145,7 @@ static inline bool strstarts(const char
*str, const char *prefix)
>> >> ? ? ? return strncmp(str, prefix, strlen(prefix)) == 0;
>> >> ?}
>> >> ?#endif
>> >> +
>> >> +extern size_t memweight(const void *ptr, size_t bytes);
>> >> +
>> >> ?#endif /* _LINUX_STRING_H_ */
>> >> diff --git a/lib/string.c b/lib/string.c
>> >> index e5878de..bf4d5a8 100644
>> >> --- a/lib/string.c
>> >> +++ b/lib/string.c
>> >> @@ -26,6 +26,7 @@
>> >> ?#include <linux/export.h>
>> >> ?#include <linux/bug.h>
>> >> ?#include <linux/errno.h>
>> >> +#include <linux/bitmap.h>
>> >>
>> >> ?#ifndef __HAVE_ARCH_STRNICMP
>> >> ?/**
>> >> @@ -824,3 +825,34 @@ void *memchr_inv(const void *start, int
c, size_t bytes)
>> >> ? ? ? return check_bytes8(start, value, bytes % 8);
>> >> ?}
>> >> ?EXPORT_SYMBOL(memchr_inv);
>> >> +
>> >> +/**
>> >> + * memweight - count the total number of bits set in memory
area
>> >> + * @ptr: pointer to the start of the area
>> >> + * @bytes: the size of the area
>> >> + */
>> >> +size_t memweight(const void *ptr, size_t bytes)
>> >> +{
>> >> + ? ? size_t w = 0;
>> >> + ? ? size_t longs;
>> >> + ? ? const unsigned char *bitmap = ptr;
>> >> +
>> >> + ? ? for (; bytes > 0 && ((unsigned long)bitmap) %
sizeof(long);
>> >> + ? ? ? ? ? ? ? ? ? ? bytes--, bitmap++)
>> >> + ? ? ? ? ? ? w += hweight8(*bitmap);
>> >> +
>> >> + ? ? longs = bytes / sizeof(long);
>> >> + ? ? if (longs) {
>> >> + ? ? ? ? ? ? BUG_ON(longs >= INT_MAX / BITS_PER_LONG);
>> >> + ? ? ? ? ? ? w += bitmap_weight((unsigned long *)bitmap,
>> >> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? longs * BITS_PER_LONG);
>> >> + ? ? ? ? ? ? bytes -= longs * sizeof(long);
>> >> + ? ? ? ? ? ? bitmap += longs * sizeof(long);
>> >> + ? ? }
>> >> +
>> >> + ? ? for (; bytes > 0; bytes--, bitmap++)
>> >> + ? ? ? ? ? ? w += hweight8(*bitmap);
>> > ?Looking at bitmap_weight() it seems this last loop is not needed.
Just
>> > pass to bitmap_weight() bytes*BITS_PER_BYTE. Also generally this
function
>> > doesn't seem necessary at all at least for ext2 & ext3
(sorry for not
>> > noticing this earlier...).
>>
>> This last loop is necessary for big-endian architecture.
>> if bytes % sizeof(long) != 0, bitmap_weight() counts one-bits in wrong
>> byte-field
>> of the last long word.
> ?Ah, right. OK. Add this to the comment before the loop please. You save
> yourself some explanations :)
OK.  Thanks for your advice again.