memweight() is the function that counts the total number of bits set
in memory area. The memory area doesn't need to be aligned to
long-word boundary unlike bitmap_weight().
Signed-off-by: Akinobu Mita <[email protected]>
Cc: Anders Larsen <[email protected]>
Cc: Alasdair Kergon <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: Laurent Pinchart <[email protected]>
Cc: [email protected]
Cc: Mark Fasheh <[email protected]>
Cc: Joel Becker <[email protected]>
Cc: [email protected]
Cc: Jan Kara <[email protected]>
Cc: [email protected]
Cc: Andrew Morton <[email protected]>
Cc: Andreas Dilger <[email protected]>
Cc: "Theodore Ts'o" <[email protected]>
---
include/linux/string.h | 3 +++
lib/string.c | 37 +++++++++++++++++++++++++++++++++++++
2 files changed, 40 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..c8b92a0 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 +825,39 @@ 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;
+ union {
+ const void *ptr;
+ const unsigned char *b;
+ unsigned long address;
+ } bitmap;
+
+ for (bitmap.ptr = ptr; bytes > 0 && bitmap.address % sizeof(long);
+ bytes--, bitmap.address++)
+ w += hweight8(*bitmap.b);
+
+ for (longs = bytes / sizeof(long); longs > 0; ) {
+ size_t bits = min_t(size_t, INT_MAX & ~(BITS_PER_LONG - 1),
+ longs * BITS_PER_LONG);
+
+ w += bitmap_weight(bitmap.ptr, bits);
+ bytes -= bits / BITS_PER_BYTE;
+ bitmap.address += bits / BITS_PER_BYTE;
+ longs -= bits / BITS_PER_LONG;
+ }
+
+ for (; bytes > 0; bytes--, bitmap.address++)
+ w += hweight8(*bitmap.b);
+
+ return w;
+}
+EXPORT_SYMBOL(memweight);
--
1.7.7.6
Use memweight() to count the total number of bits clear in memory area.
This change only affects the code segments enabled by EXT3FS_DEBUG.
This also fixes printk format warning that only reveals with EXT3FS_DEBUG.
Signed-off-by: Akinobu Mita <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Andreas Dilger <[email protected]>
Cc: [email protected]
---
fs/ext3/Makefile | 2 +-
fs/ext3/balloc.c | 5 +++--
fs/ext3/bitmap.c | 30 ------------------------------
fs/ext3/ext3.h | 2 --
fs/ext3/ialloc.c | 4 +++-
5 files changed, 7 insertions(+), 36 deletions(-)
delete mode 100644 fs/ext3/bitmap.c
diff --git a/fs/ext3/Makefile b/fs/ext3/Makefile
index e77766a..ce93e94 100644
--- a/fs/ext3/Makefile
+++ b/fs/ext3/Makefile
@@ -4,7 +4,7 @@
obj-$(CONFIG_EXT3_FS) += ext3.o
-ext3-y := balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o \
+ext3-y := balloc.o dir.o file.o fsync.o ialloc.o inode.o \
ioctl.o namei.o super.o symlink.o hash.o resize.o ext3_jbd.o
ext3-$(CONFIG_EXT3_FS_XATTR) += xattr.o xattr_user.o xattr_trusted.o
diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
index baac1b1..676bd53 100644
--- a/fs/ext3/balloc.c
+++ b/fs/ext3/balloc.c
@@ -1804,7 +1804,8 @@ ext3_fsblk_t ext3_count_free_blocks(struct super_block *sb)
if (bitmap_bh == NULL)
continue;
- x = ext3_count_free(bitmap_bh, sb->s_blocksize);
+ x = sb->s_blocksize * BITS_PER_BYTE -
+ memweight(bitmap_bh->b_data, sb->s_blocksize);
printk("group %d: stored = %d, counted = %lu\n",
i, le16_to_cpu(gdp->bg_free_blocks_count), x);
bitmap_count += x;
@@ -1812,7 +1813,7 @@ ext3_fsblk_t ext3_count_free_blocks(struct super_block *sb)
brelse(bitmap_bh);
printk("ext3_count_free_blocks: stored = "E3FSBLK
", computed = "E3FSBLK", "E3FSBLK"\n",
- le32_to_cpu(es->s_free_blocks_count),
+ (ext3_fsblk_t)le32_to_cpu(es->s_free_blocks_count),
desc_count, bitmap_count);
return bitmap_count;
#else
diff --git a/fs/ext3/bitmap.c b/fs/ext3/bitmap.c
deleted file mode 100644
index 909d13e..0000000
--- a/fs/ext3/bitmap.c
+++ /dev/null
@@ -1,30 +0,0 @@
-/*
- * linux/fs/ext3/bitmap.c
- *
- * Copyright (C) 1992, 1993, 1994, 1995
- * Remy Card ([email protected])
- * Laboratoire MASI - Institut Blaise Pascal
- * Universite Pierre et Marie Curie (Paris VI)
- */
-
-#include "ext3.h"
-
-#ifdef EXT3FS_DEBUG
-
-static const int nibblemap[] = {4, 3, 3, 2, 3, 2, 2, 1, 3, 2, 2, 1, 2, 1, 1, 0};
-
-unsigned long ext3_count_free (struct buffer_head * map, unsigned int numchars)
-{
- unsigned int i;
- unsigned long sum = 0;
-
- if (!map)
- return (0);
- for (i = 0; i < numchars; i++)
- sum += nibblemap[map->b_data[i] & 0xf] +
- nibblemap[(map->b_data[i] >> 4) & 0xf];
- return (sum);
-}
-
-#endif /* EXT3FS_DEBUG */
-
diff --git a/fs/ext3/ext3.h b/fs/ext3/ext3.h
index b6515fd..5c6246d 100644
--- a/fs/ext3/ext3.h
+++ b/fs/ext3/ext3.h
@@ -1029,8 +1029,6 @@ extern struct inode * ext3_orphan_get (struct super_block *, unsigned long);
extern unsigned long ext3_count_free_inodes (struct super_block *);
extern unsigned long ext3_count_dirs (struct super_block *);
extern void ext3_check_inodes_bitmap (struct super_block *);
-extern unsigned long ext3_count_free (struct buffer_head *, unsigned);
-
/* inode.c */
int ext3_forget(handle_t *handle, int is_metadata, struct inode *inode,
diff --git a/fs/ext3/ialloc.c b/fs/ext3/ialloc.c
index e3c39e4..b58c8e2 100644
--- a/fs/ext3/ialloc.c
+++ b/fs/ext3/ialloc.c
@@ -683,7 +683,9 @@ unsigned long ext3_count_free_inodes (struct super_block * sb)
if (!bitmap_bh)
continue;
- x = ext3_count_free(bitmap_bh, EXT3_INODES_PER_GROUP(sb) / 8);
+ x = EXT3_INODES_PER_GROUP(sb) / 8 * BITS_PER_BYTE -
+ memweight(bitmap_bh->b_data,
+ EXT3_INODES_PER_GROUP(sb) / 8);
printk("group %d: stored = %d, counted = %lu\n",
i, le16_to_cpu(gdp->bg_free_inodes_count), x);
bitmap_count += x;
--
1.7.7.6
Use memweight() to count the total number of bits clear in memory area.
This change only affects the code segments enabled by EXT4FS_DEBUG.
Signed-off-by: Akinobu Mita <[email protected]>
Cc: "Theodore Ts'o" <[email protected]>
Cc: Andreas Dilger <[email protected]>
Cc: [email protected]
---
fs/ext4/Makefile | 2 +-
fs/ext4/balloc.c | 3 ++-
fs/ext4/bitmap.c | 31 -------------------------------
fs/ext4/ext4.h | 3 ---
fs/ext4/ialloc.c | 4 +++-
5 files changed, 6 insertions(+), 37 deletions(-)
delete mode 100644 fs/ext4/bitmap.c
diff --git a/fs/ext4/Makefile b/fs/ext4/Makefile
index 56fd8f86..0caff90 100644
--- a/fs/ext4/Makefile
+++ b/fs/ext4/Makefile
@@ -4,7 +4,7 @@
obj-$(CONFIG_EXT4_FS) += ext4.o
-ext4-y := balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o page-io.o \
+ext4-y := balloc.o dir.o file.o fsync.o ialloc.o inode.o page-io.o \
ioctl.o namei.o super.o symlink.o hash.o resize.o extents.o \
ext4_jbd2.o migrate.o mballoc.o block_validity.o move_extent.o \
mmp.o indirect.o
diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 4bbd07a..57e3bfb 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -584,7 +584,8 @@ ext4_fsblk_t ext4_count_free_clusters(struct super_block *sb)
if (bitmap_bh == NULL)
continue;
- x = ext4_count_free(bitmap_bh, sb->s_blocksize);
+ x = sb->s_blocksize * BITS_PER_BYTE -
+ memweight(bitmap_bh->b_data, sb->s_blocksize);
printk(KERN_DEBUG "group %u: stored = %d, counted = %u\n",
i, ext4_free_group_clusters(sb, gdp), x);
bitmap_count += x;
diff --git a/fs/ext4/bitmap.c b/fs/ext4/bitmap.c
deleted file mode 100644
index fa3af81..0000000
--- a/fs/ext4/bitmap.c
+++ /dev/null
@@ -1,31 +0,0 @@
-/*
- * linux/fs/ext4/bitmap.c
- *
- * Copyright (C) 1992, 1993, 1994, 1995
- * Remy Card ([email protected])
- * Laboratoire MASI - Institut Blaise Pascal
- * Universite Pierre et Marie Curie (Paris VI)
- */
-
-#include <linux/buffer_head.h>
-#include <linux/jbd2.h>
-#include "ext4.h"
-
-#ifdef EXT4FS_DEBUG
-
-static const int nibblemap[] = {4, 3, 3, 2, 3, 2, 2, 1, 3, 2, 2, 1, 2, 1, 1, 0};
-
-unsigned int ext4_count_free(struct buffer_head *map, unsigned int numchars)
-{
- unsigned int i, sum = 0;
-
- if (!map)
- return 0;
- for (i = 0; i < numchars; i++)
- sum += nibblemap[map->b_data[i] & 0xf] +
- nibblemap[(map->b_data[i] >> 4) & 0xf];
- return sum;
-}
-
-#endif /* EXT4FS_DEBUG */
-
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 0e01e90..9c616d9 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1782,9 +1782,6 @@ struct mmpd_data {
# define ATTRIB_NORET __attribute__((noreturn))
# define NORET_AND noreturn,
-/* bitmap.c */
-extern unsigned int ext4_count_free(struct buffer_head *, unsigned);
-
/* balloc.c */
extern unsigned int ext4_block_group(struct super_block *sb,
ext4_fsblk_t blocknr);
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 409c2ee..2452bb7 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -1011,7 +1011,9 @@ unsigned long ext4_count_free_inodes(struct super_block *sb)
if (!bitmap_bh)
continue;
- x = ext4_count_free(bitmap_bh, EXT4_INODES_PER_GROUP(sb) / 8);
+ x = EXT4_INODES_PER_GROUP(sb) / 8 * BITS_PER_BYTE -
+ memweight(bitmap_bh->b_data,
+ EXT4_INODES_PER_GROUP(sb) / 8);
printk(KERN_DEBUG "group %lu: stored = %d, counted = %lu\n",
(unsigned long) i, ext4_free_inodes_count(sb, gdp), x);
bitmap_count += x;
--
1.7.7.6
Use memweight() to count the total number of bits clear in memory area.
This change only affects the code segments enabled by EXT2FS_DEBUG.
This also fixes printk format warning that only reveals with EXT2FS_DEBUG.
Signed-off-by: Akinobu Mita <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: [email protected]
---
fs/ext2/balloc.c | 22 ++--------------------
fs/ext2/ext2.h | 1 -
fs/ext2/ialloc.c | 5 ++++-
3 files changed, 6 insertions(+), 22 deletions(-)
diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
index a8cbe1b..3351731 100644
--- a/fs/ext2/balloc.c
+++ b/fs/ext2/balloc.c
@@ -1443,25 +1443,6 @@ ext2_fsblk_t ext2_new_block(struct inode *inode, unsigned long goal, int *errp)
return ext2_new_blocks(inode, goal, &count, errp);
}
-#ifdef EXT2FS_DEBUG
-
-static const int nibblemap[] = {4, 3, 3, 2, 3, 2, 2, 1, 3, 2, 2, 1, 2, 1, 1, 0};
-
-unsigned long ext2_count_free (struct buffer_head * map, unsigned int numchars)
-{
- unsigned int i;
- unsigned long sum = 0;
-
- if (!map)
- return (0);
- for (i = 0; i < numchars; i++)
- sum += nibblemap[map->b_data[i] & 0xf] +
- nibblemap[(map->b_data[i] >> 4) & 0xf];
- return (sum);
-}
-
-#endif /* EXT2FS_DEBUG */
-
unsigned long ext2_count_free_blocks (struct super_block * sb)
{
struct ext2_group_desc * desc;
@@ -1485,7 +1466,8 @@ unsigned long ext2_count_free_blocks (struct super_block * sb)
if (!bitmap_bh)
continue;
- x = ext2_count_free(bitmap_bh, sb->s_blocksize);
+ x = sb->s_blocksize * BITS_PER_BYTE -
+ memweight(bitmap_bh->b_data, sb->s_blocksize);
printk ("group %d: stored = %d, counted = %lu\n",
i, le16_to_cpu(desc->bg_free_blocks_count), x);
bitmap_count += x;
diff --git a/fs/ext2/ext2.h b/fs/ext2/ext2.h
index 0b2b4db..de2a4e5 100644
--- a/fs/ext2/ext2.h
+++ b/fs/ext2/ext2.h
@@ -745,7 +745,6 @@ extern struct inode * ext2_new_inode (struct inode *, umode_t, const struct qstr
extern void ext2_free_inode (struct inode *);
extern unsigned long ext2_count_free_inodes (struct super_block *);
extern void ext2_check_inodes_bitmap (struct super_block *);
-extern unsigned long ext2_count_free (struct buffer_head *, unsigned);
/* inode.c */
extern struct inode *ext2_iget (struct super_block *, unsigned long);
diff --git a/fs/ext2/ialloc.c b/fs/ext2/ialloc.c
index 8b15cf8..82139c4 100644
--- a/fs/ext2/ialloc.c
+++ b/fs/ext2/ialloc.c
@@ -639,13 +639,16 @@ unsigned long ext2_count_free_inodes (struct super_block * sb)
if (!bitmap_bh)
continue;
- x = ext2_count_free(bitmap_bh, EXT2_INODES_PER_GROUP(sb) / 8);
+ x = EXT2_INODES_PER_GROUP(sb) / 8 * BITS_PER_BYTE -
+ memweight(bitmap_bh->b_data,
+ EXT2_INODES_PER_GROUP(sb) / 8);
printk("group %d: stored = %d, counted = %u\n",
i, le16_to_cpu(desc->bg_free_inodes_count), x);
bitmap_count += x;
}
brelse(bitmap_bh);
printk("ext2_count_free_inodes: stored = %lu, computed = %lu, %lu\n",
+ (unsigned long)
percpu_counter_read(&EXT2_SB(sb)->s_freeinodes_counter),
desc_count, bitmap_count);
return desc_count;
--
1.7.7.6
On Sun 20-05-12 22:23:14, Akinobu Mita wrote:
> memweight() is the function that counts the total number of bits set
> in memory area. The memory area doesn't need to be aligned to
> long-word boundary unlike bitmap_weight().
Thanks for the patch. I have some comments below.
> Signed-off-by: Akinobu Mita <[email protected]>
> Cc: Anders Larsen <[email protected]>
> Cc: Alasdair Kergon <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Cc: Laurent Pinchart <[email protected]>
> Cc: [email protected]
> Cc: Mark Fasheh <[email protected]>
> Cc: Joel Becker <[email protected]>
> Cc: [email protected]
> Cc: Jan Kara <[email protected]>
> Cc: [email protected]
> Cc: Andrew Morton <[email protected]>
> Cc: Andreas Dilger <[email protected]>
> Cc: "Theodore Ts'o" <[email protected]>
> ---
> include/linux/string.h | 3 +++
> lib/string.c | 37 +++++++++++++++++++++++++++++++++++++
> 2 files changed, 40 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..c8b92a0 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 +825,39 @@ 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;
> + union {
> + const void *ptr;
> + const unsigned char *b;
> + unsigned long address;
> + } bitmap;
Ugh, this is ugly and mostly unnecessary. Just use "const unsigned char
*bitmap".
> +
> + for (bitmap.ptr = ptr; bytes > 0 && bitmap.address % sizeof(long);
> + bytes--, bitmap.address++)
> + w += hweight8(*bitmap.b);
This can be:
count = ((unsigned long)bitmap) % sizeof(long);
while (count--) {
w += hweight(*bitmap);
bitmap++;
bytes--;
}
> +
> + for (longs = bytes / sizeof(long); longs > 0; ) {
> + size_t bits = min_t(size_t, INT_MAX & ~(BITS_PER_LONG - 1),
> + longs * BITS_PER_LONG);
I find it highly unlikely that someone would have such a large bitmap
(256 MB or more on 32-bit). Also the condition as you wrote it can just
overflow so it won't have the desired effect. Just do
BUG_ON(longs >= ULONG_MAX / BITS_PER_LONG);
and remove the loop completely. If someone comes with such a huge bitmap,
the code can be modified easily (after really closely inspecting whether
such a huge bitmap is really well justified).
> +
> + w += bitmap_weight(bitmap.ptr, bits);
> + bytes -= bits / BITS_PER_BYTE;
> + bitmap.address += bits / BITS_PER_BYTE;
> + longs -= bits / BITS_PER_LONG;
> + }
> +
> + for (; bytes > 0; bytes--, bitmap.address++)
> + w += hweight8(*bitmap.b);
> +
> + return w;
> +}
> +EXPORT_SYMBOL(memweight);
Honza
--
Jan Kara <[email protected]>
SUSE Labs, CR
2012/5/23 Jan Kara <[email protected]>:
> On Sun 20-05-12 22:23:14, Akinobu Mita wrote:
>> memweight() is the function that counts the total number of bits set
>> in memory area. ?The memory area doesn't need to be aligned to
>> long-word boundary unlike bitmap_weight().
> ?Thanks for the patch. I have some comments below.
Thanks for the review.
>> @@ -824,3 +825,39 @@ 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;
>> + ? ? union {
>> + ? ? ? ? ? ? const void *ptr;
>> + ? ? ? ? ? ? const unsigned char *b;
>> + ? ? ? ? ? ? unsigned long address;
>> + ? ? } bitmap;
> ?Ugh, this is ugly and mostly unnecessary. Just use "const unsigned char
> *bitmap".
>
>> +
>> + ? ? for (bitmap.ptr = ptr; bytes > 0 && bitmap.address % sizeof(long);
>> + ? ? ? ? ? ? ? ? ? ? bytes--, bitmap.address++)
>> + ? ? ? ? ? ? w += hweight8(*bitmap.b);
> ?This can be:
> ? ? ? ?count = ((unsigned long)bitmap) % sizeof(long);
The count should be the size of unaligned area and it can be greater than
bytes. So
count = min(bytes,
sizeof(long) - ((unsigned long)bitmap) % sizeof(long));
> ? ? ? ?while (count--) {
> ? ? ? ? ? ? ? ?w += hweight(*bitmap);
> ? ? ? ? ? ? ? ?bitmap++;
> ? ? ? ? ? ? ? ?bytes--;
> ? ? ? ?}
>> +
>> + ? ? for (longs = bytes / sizeof(long); longs > 0; ) {
>> + ? ? ? ? ? ? size_t bits = min_t(size_t, INT_MAX & ~(BITS_PER_LONG - 1),
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? longs * BITS_PER_LONG);
> ?I find it highly unlikely that someone would have such a large bitmap
> (256 MB or more on 32-bit). Also the condition as you wrote it can just
> overflow so it won't have the desired effect. Just do
> ? ? ? ?BUG_ON(longs >= ULONG_MAX / BITS_PER_LONG);
The bits argument of bitmap_weight() is int type. So this should be
BUG_ON(longs >= INT_MAX / BITS_PER_LONG);
> and remove the loop completely. If someone comes with such a huge bitmap,
> the code can be modified easily (after really closely inspecting whether
> such a huge bitmap is really well justified).
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);
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;
}
On Wed 23-05-12 21:12:18, Akinobu Mita wrote:
> 2012/5/23 Jan Kara <[email protected]>:
> > On Sun 20-05-12 22:23:14, Akinobu Mita wrote:
> >> memweight() is the function that counts the total number of bits set
> >> in memory area. ?The memory area doesn't need to be aligned to
> >> long-word boundary unlike bitmap_weight().
> > ?Thanks for the patch. I have some comments below.
>
> Thanks for the review.
>
> >> @@ -824,3 +825,39 @@ 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;
> >> + ? ? union {
> >> + ? ? ? ? ? ? const void *ptr;
> >> + ? ? ? ? ? ? const unsigned char *b;
> >> + ? ? ? ? ? ? unsigned long address;
> >> + ? ? } bitmap;
> > ?Ugh, this is ugly and mostly unnecessary. Just use "const unsigned char
> > *bitmap".
> >
> >> +
> >> + ? ? for (bitmap.ptr = ptr; bytes > 0 && bitmap.address % sizeof(long);
> >> + ? ? ? ? ? ? ? ? ? ? bytes--, bitmap.address++)
> >> + ? ? ? ? ? ? w += hweight8(*bitmap.b);
> > ?This can be:
> > ? ? ? ?count = ((unsigned long)bitmap) % sizeof(long);
>
> The count should be the size of unaligned area and it can be greater than
> bytes. So
>
> count = min(bytes,
> sizeof(long) - ((unsigned long)bitmap) % sizeof(long));
You are right, I didn't quite think this through.
> > ? ? ? ?while (count--) {
> > ? ? ? ? ? ? ? ?w += hweight(*bitmap);
> > ? ? ? ? ? ? ? ?bitmap++;
> > ? ? ? ? ? ? ? ?bytes--;
> > ? ? ? ?}
> >> +
> >> + ? ? for (longs = bytes / sizeof(long); longs > 0; ) {
> >> + ? ? ? ? ? ? size_t bits = min_t(size_t, INT_MAX & ~(BITS_PER_LONG - 1),
> >> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? longs * BITS_PER_LONG);
> > ?I find it highly unlikely that someone would have such a large bitmap
> > (256 MB or more on 32-bit). Also the condition as you wrote it can just
> > overflow so it won't have the desired effect. Just do
> > ? ? ? ?BUG_ON(longs >= ULONG_MAX / BITS_PER_LONG);
>
> The bits argument of bitmap_weight() is int type. So this should be
>
> BUG_ON(longs >= INT_MAX / BITS_PER_LONG);
OK, I didn't check and thought it's size_t.
> > and remove the loop completely. If someone comes with such a huge bitmap,
> > the code can be modified easily (after really closely inspecting whether
> > such a huge bitmap is really well justified).
>
> 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);
> 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;
> }
Yup, this looks much more readable. Thanks!
Honza
--
Jan Kara <[email protected]>
SUSE Labs, CR
On Wed, May 23, 2012 at 09:12:18PM +0900, Akinobu Mita wrote:
> size_t memweight(const void *ptr, size_t bytes)
Why should this return size_t instead of unsigned long?
> {
> 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);
> 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;
> }
bitmap_weight copes with a bitmask that isn't a multiple of BITS_PER_LONG
in size already. So I think this can be done as:
unsigned long memweight(const void *s, size_t n)
{
const unsigned char *ptr = s;
unsigned long r = 0;
while (n > 0 && (unsigned long)ptr % sizeof(long)) {
r += hweight8(*ptr);
n--;
ptr++;
}
BUG_ON(n >= INT_MAX / 8)
return r + bitmap_weight((unsigned long *)ptr, n * 8);
}
--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."
2012/5/23 Matthew Wilcox <[email protected]>:
> On Wed, May 23, 2012 at 09:12:18PM +0900, Akinobu Mita wrote:
>> size_t memweight(const void *ptr, size_t bytes)
>
> Why should this return size_t instead of unsigned long?
I just use the same type as the bytes argument without mature
consideration. If unsigned long is better than size_t, I'll
change the return type.
>> {
>> ? ? ? 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);
>> ? ? ? 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;
>> }
>
> bitmap_weight copes with a bitmask that isn't a multiple of BITS_PER_LONG
> in size already. ?So I think this can be done as:
>
> unsigned long memweight(const void *s, size_t n)
> {
> ? ? ? ?const unsigned char *ptr = s;
> ? ? ? ?unsigned long r = 0;
>
> ? ? ? ?while (n > 0 && (unsigned long)ptr % sizeof(long)) {
> ? ? ? ? ? ? ? ?r += hweight8(*ptr);
> ? ? ? ? ? ? ? ?n--;
> ? ? ? ? ? ? ? ?ptr++;
> ? ? ? ?}
>
> ? ? ? ?BUG_ON(n >= INT_MAX / 8)
>
> ? ? ? ?return r + bitmap_weight((unsigned long *)ptr, n * 8);
> }
This works perfectly on little-endian machines. But it doesn't work
on big-endian machines, if the bottom edge of memory area is not
aligned on long word boundary.