Messages in this thread | | | Subject | Re: [PATCH] xen-blkfront: Use the bitmap API when applicable | From | Christophe JAILLET <> | Date | Sat, 4 Dec 2021 07:57:21 +0100 |
| |
Le 03/12/2021 à 22:04, Boris Ostrovsky a écrit : > > On 12/3/21 10:54 AM, Christophe JAILLET wrote: >> Le 03/12/2021 à 04:03, Joe Perches a écrit : >> >> I get your point now, and I agree with you. >> >> Maybe something as what is done in mc-entity.c? >> Explicitly require more bits (which will be allocated anyway), instead >> of taking advantage (read "hoping") that it will be done. >> >> Could be: >> >> @@ -440,26 +440,25 @@ static int xlbd_reserve_minors(unsigned int >> minor, unsigned int nr) >> int rc; >> >> if (end > nr_minors) { >> unsigned long *bitmap, *old; >> >> - bitmap = kcalloc(BITS_TO_LONGS(end), sizeof(*bitmap), >> - GFP_KERNEL); >> + end = ALIGN(end, BITS_PER_LONG); >> + bitmap = bitmap_zalloc(end, GFP_KERNEL); >> if (bitmap == NULL) >> return -ENOMEM; >> >> spin_lock(&minor_lock); >> if (end > nr_minors) { >> old = minors; >> - memcpy(bitmap, minors, >> - BITS_TO_LONGS(nr_minors) * sizeof(*bitmap)); >> + bitmap_copy(bitmap, minors, nr_minors); >> minors = bitmap; >> - nr_minors = BITS_TO_LONGS(end) * BITS_PER_LONG; >> + nr_minors = end; >> } else >> old = bitmap; >> spin_unlock(&minor_lock); >> - kfree(old); >> + bitmap_free(old); >> } >> >> spin_lock(&minor_lock); >> if (find_next_bit(minors, end, minor) >= end) { > > > I don't think this will work anymore, we may now fail if another thread > gets a minor above the original (i.e. no aligned) @end. >
So, maybe adding an "official" 'bitmap_size()' (which is already existing and duplicated in a few places) would ease things.
It would replace the 'nr_minors = BITS_TO_LONGS(end) * BITS_PER_LONG;' and hide the implementation details of the bitmap API.
Something like: static __always_inline size_t bitmap_size(unsigned long nr_bits) { return BITS_TO_LONGS(nr_bits) * sizeof(long); }
CJ
> > -boris >
| |