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@xxxxxxxxx> > Cc: Anders Larsen <al@xxxxxxxxxxx> > Cc: Alasdair Kergon <agk@xxxxxxxxxx> > Cc: dm-devel@xxxxxxxxxx > Cc: linux-fsdevel@xxxxxxxxxxxxxxx > Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> > Cc: linux-media@xxxxxxxxxxxxxxx > Cc: Mark Fasheh <mfasheh@xxxxxxxx> > Cc: Joel Becker <jlbec@xxxxxxxxxxxx> > Cc: ocfs2-devel@xxxxxxxxxxxxxx > Cc: Jan Kara <jack@xxxxxxx> > Cc: linux-ext4@xxxxxxxxxxxxxxx > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Andreas Dilger <adilger.kernel@xxxxxxxxx> > Cc: "Theodore Ts'o" <tytso@xxxxxxx> > Cc: Matthew Wilcox <matthew@xxxxxx> > --- > > 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 -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel