On Wednesday November 9, mingz@xxxxxxxxxxx wrote:
> could anybody help me on this? thanks!
>
> see if we call bitmap_zero(dst, 2), it will do *dst = 0UL and thus clear
> whole *dst, but what if we intent to clear 2 bits? not 32bits?
bitmap_zero isn't intended for zeroing just a few bits in a bitmap.
It is for zeroing an entire bitmap, and you tell it how big the bitmap
is. So this function will always zero at least the whole bitmap, and
maybe a bit more. as bitmaps are always allocated as an array of
'unsigned long', there it no risk it over-running the space allocated.
Hope that helps.
NeilBrown
>
> static inline void bitmap_zero(unsigned long *dst, int nbits)
> {
> if (nbits <= BITS_PER_LONG)
> *dst = 0UL;
> else {
> int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
> memset(dst, 0, len);
> }
> }
>
>
> Ming
>
>
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