| Message ID | 1338644416-11417-1-git-send-email-akinobu.mita@gmail.com |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
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@gmail.com> > Cc: Anders Larsen <al@alarsen.net> > Cc: Alasdair Kergon <agk@redhat.com> > Cc: dm-devel@redhat.com > Cc: linux-fsdevel@vger.kernel.org > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > Cc: linux-media@vger.kernel.org > Cc: Mark Fasheh <mfasheh@suse.com> > Cc: Joel Becker <jlbec@evilplan.org> > Cc: ocfs2-devel@oss.oracle.com > Cc: Jan Kara <jack@suse.cz> > Cc: linux-ext4@vger.kernel.org > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Andreas Dilger <adilger.kernel@dilger.ca> > Cc: "Theodore Ts'o" <tytso@mit.edu> > Cc: Matthew Wilcox <matthew@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...). Honza
2012/6/4 Jan Kara <jack@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@gmail.com> >> Cc: Anders Larsen <al@alarsen.net> >> Cc: Alasdair Kergon <agk@redhat.com> >> Cc: dm-devel@redhat.com >> Cc: linux-fsdevel@vger.kernel.org >> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> >> Cc: linux-media@vger.kernel.org >> Cc: Mark Fasheh <mfasheh@suse.com> >> Cc: Joel Becker <jlbec@evilplan.org> >> Cc: ocfs2-devel@oss.oracle.com >> Cc: Jan Kara <jack@suse.cz> >> Cc: linux-ext4@vger.kernel.org >> Cc: Andrew Morton <akpm@linux-foundation.org> >> Cc: Andreas Dilger <adilger.kernel@dilger.ca> >> Cc: "Theodore Ts'o" <tytso@mit.edu> >> Cc: Matthew Wilcox <matthew@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. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon 04-06-12 20:46:14, Akinobu Mita wrote: > 2012/6/4 Jan Kara <jack@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@gmail.com> > >> Cc: Anders Larsen <al@alarsen.net> > >> Cc: Alasdair Kergon <agk@redhat.com> > >> Cc: dm-devel@redhat.com > >> Cc: linux-fsdevel@vger.kernel.org > >> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > >> Cc: linux-media@vger.kernel.org > >> Cc: Mark Fasheh <mfasheh@suse.com> > >> Cc: Joel Becker <jlbec@evilplan.org> > >> Cc: ocfs2-devel@oss.oracle.com > >> Cc: Jan Kara <jack@suse.cz> > >> Cc: linux-ext4@vger.kernel.org > >> Cc: Andrew Morton <akpm@linux-foundation.org> > >> Cc: Andreas Dilger <adilger.kernel@dilger.ca> > >> Cc: "Theodore Ts'o" <tytso@mit.edu> > >> Cc: Matthew Wilcox <matthew@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 :) Honza
2012/6/4 Jan Kara <jack@suse.cz>: > On Mon 04-06-12 20:46:14, Akinobu Mita wrote: >> 2012/6/4 Jan Kara <jack@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. áUnlike 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@gmail.com> >> >> Cc: Anders Larsen <al@alarsen.net> >> >> Cc: Alasdair Kergon <agk@redhat.com> >> >> Cc: dm-devel@redhat.com >> >> Cc: linux-fsdevel@vger.kernel.org >> >> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> >> >> Cc: linux-media@vger.kernel.org >> >> Cc: Mark Fasheh <mfasheh@suse.com> >> >> Cc: Joel Becker <jlbec@evilplan.org> >> >> Cc: ocfs2-devel@oss.oracle.com >> >> Cc: Jan Kara <jack@suse.cz> >> >> Cc: linux-ext4@vger.kernel.org >> >> Cc: Andrew Morton <akpm@linux-foundation.org> >> >> Cc: Andreas Dilger <adilger.kernel@dilger.ca> >> >> Cc: "Theodore Ts'o" <tytso@mit.edu> >> >> Cc: Matthew Wilcox <matthew@wil.cx> >> >> --- >> >> >> >> v2: simplify memweight(), adviced by Jan Kara >> >> >> >> áinclude/linux/string.h | á á3 +++ >> >> álib/string.c á á á á á | á 32 ++++++++++++++++++++++++++++++++ >> >> á2 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) >> >> á á á return strncmp(str, prefix, strlen(prefix)) == 0; >> >> á} >> >> á#endif >> >> + >> >> +extern size_t memweight(const void *ptr, size_t bytes); >> >> + >> >> á#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 @@ >> >> á#include <linux/export.h> >> >> á#include <linux/bug.h> >> >> á#include <linux/errno.h> >> >> +#include <linux/bitmap.h> >> >> >> >> á#ifndef __HAVE_ARCH_STRNICMP >> >> á/** >> >> @@ -824,3 +825,34 @@ void *memchr_inv(const void *start, int c, size_t bytes) >> >> á á á return check_bytes8(start, value, bytes % 8); >> >> á} >> >> áEXPORT_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) >> >> +{ >> >> + á á size_t w = 0; >> >> + á á size_t longs; >> >> + á á const unsigned char *bitmap = ptr; >> >> + >> >> + á á for (; bytes > 0 && ((unsigned long)bitmap) % sizeof(long); >> >> + á á á á á á á á á á bytes--, bitmap++) >> >> + á á á á á á w += hweight8(*bitmap); >> >> + >> >> + á á longs = bytes / sizeof(long); >> >> + á á if (longs) { >> >> + á á á á á á BUG_ON(longs >= INT_MAX / BITS_PER_LONG); >> >> + á á á á á á w += bitmap_weight((unsigned long *)bitmap, >> >> + á á á á á á á á á á á á á á longs * BITS_PER_LONG); >> >> + á á á á á á bytes -= longs * sizeof(long); >> >> + á á á á á á bitmap += longs * sizeof(long); >> >> + á á } >> >> + >> >> + á á for (; bytes > 0; bytes--, bitmap++) >> >> + á á á á á á w += hweight8(*bitmap); >> > áLooking 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. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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);
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@gmail.com> Cc: Anders Larsen <al@alarsen.net> Cc: Alasdair Kergon <agk@redhat.com> Cc: dm-devel@redhat.com Cc: linux-fsdevel@vger.kernel.org Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Cc: linux-media@vger.kernel.org Cc: Mark Fasheh <mfasheh@suse.com> Cc: Joel Becker <jlbec@evilplan.org> Cc: ocfs2-devel@oss.oracle.com Cc: Jan Kara <jack@suse.cz> Cc: linux-ext4@vger.kernel.org Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andreas Dilger <adilger.kernel@dilger.ca> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Matthew Wilcox <matthew@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(-)