From: "Wang, Wei W" <wei.w.wang@intel.com>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: "virtio-dev@lists.oasis-open.org"
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Subject: RE: [PATCH v18 05/10] xbitmap: add more operations
Date: Fri, 1 Dec 2017 15:09:08 +0000 [thread overview]
Message-ID: <286AC319A985734F985F78AFA26841F739376DA1@shsmsx102.ccr.corp.intel.com> (raw)
In-Reply-To: <201712012202.BDE13557.MJFQLtOOHVOFSF@I-love.SAKURA.ne.jp>
On Friday, December 1, 2017 9:02 PM, Tetsuo Handa wrote:
> Wei Wang wrote:
> > On 11/30/2017 06:34 PM, Tetsuo Handa wrote:
> > > Wei Wang wrote:
> > >> + * @start: the start of the bit range, inclusive
> > >> + * @end: the end of the bit range, inclusive
> > >> + *
> > >> + * This function is used to clear a bit in the xbitmap. If all the
> > >> +bits of the
> > >> + * bitmap are 0, the bitmap will be freed.
> > >> + */
> > >> +void xb_clear_bit_range(struct xb *xb, unsigned long start,
> > >> +unsigned long end) {
> > >> + struct radix_tree_root *root = &xb->xbrt;
> > >> + struct radix_tree_node *node;
> > >> + void **slot;
> > >> + struct ida_bitmap *bitmap;
> > >> + unsigned int nbits;
> > >> +
> > >> + for (; start < end; start = (start | (IDA_BITMAP_BITS - 1)) + 1) {
> > >> + unsigned long index = start / IDA_BITMAP_BITS;
> > >> + unsigned long bit = start % IDA_BITMAP_BITS;
> > >> +
> > >> + bitmap = __radix_tree_lookup(root, index, &node, &slot);
> > >> + if (radix_tree_exception(bitmap)) {
> > >> + unsigned long ebit = bit + 2;
> > >> + unsigned long tmp = (unsigned long)bitmap;
> > >> +
> > >> + nbits = min(end - start + 1, BITS_PER_LONG - ebit);
> > > "nbits = min(end - start + 1," seems to expect that start == end is
> > > legal for clearing only 1 bit. But this function is no-op if start == end.
> > > Please clarify what "inclusive" intended.
> >
> > If xb_clear_bit_range(xb,10,10), then it is effectively the same as
> > xb_clear_bit(10). Why would it be illegal?
> >
> > "@start inclusive" means that the @start will also be included to be
> > cleared.
>
> If start == end is legal,
>
> for (; start < end; start = (start | (IDA_BITMAP_BITS - 1)) + 1) {
>
> makes this loop do nothing because 10 < 10 is false.
How about "start <= end "?
Best,
Wei
next prev parent reply other threads:[~2017-12-01 15:09 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-29 13:55 [PATCH v18 00/10] Virtio-balloon Enhancement Wei Wang
2017-11-29 13:55 ` [PATCH v18 01/10] idr: add #include <linux/bug.h> Wei Wang
2017-11-30 0:58 ` Matthew Wilcox
2017-11-30 7:07 ` Michal Hocko
2017-11-30 21:49 ` Andrew Morton
2017-11-29 13:55 ` [PATCH v18 02/10] radix tree test suite: remove ARRAY_SIZE to avoid redefinition Wei Wang
2017-11-29 13:55 ` [PATCH v18 03/10] xbitmap: Introduce xbitmap Wei Wang
2017-11-29 13:55 ` [PATCH v18 04/10] xbitmap: potential improvement Wei Wang
2017-11-29 13:55 ` [PATCH v18 05/10] xbitmap: add more operations Wei Wang
2017-11-30 10:34 ` Tetsuo Handa
2017-11-30 13:35 ` Tetsuo Handa
2017-11-30 14:39 ` Matthew Wilcox
2017-12-03 1:44 ` Tetsuo Handa
2017-12-01 8:02 ` Wei Wang
2017-12-01 13:02 ` Tetsuo Handa
2017-12-01 14:13 ` Matthew Wilcox
2017-12-01 15:09 ` Wang, Wei W [this message]
2017-12-01 17:25 ` Matthew Wilcox
2017-12-03 1:50 ` Tetsuo Handa
2017-12-07 12:01 ` Wei Wang
2017-12-07 15:41 ` Michael S. Tsirkin
2017-11-29 13:55 ` [PATCH v18 06/10] virtio_ring: add a new API, virtqueue_add_one_desc Wei Wang
2017-11-30 19:38 ` Michael S. Tsirkin
2017-12-01 8:06 ` Wei Wang
2017-11-29 13:55 ` [PATCH v18 07/10] virtio-balloon: VIRTIO_BALLOON_F_SG Wei Wang
2017-11-30 10:35 ` Tetsuo Handa
2017-11-30 16:25 ` Wang, Wei W
2017-12-01 15:38 ` Michael S. Tsirkin
2017-12-04 3:46 ` Wei Wang
2017-11-29 13:55 ` [PATCH v18 08/10] mm: support reporting free page blocks Wei Wang
2017-11-29 13:55 ` [PATCH v18 09/10] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_VQ Wei Wang
2017-11-29 13:55 ` [PATCH v18 10/10] virtio-balloon: don't report free pages when page poisoning is enabled Wei Wang
2017-12-01 15:49 ` Michael S. Tsirkin
2017-12-04 5:39 ` Wei Wang
2017-12-11 6:38 ` Wei Wang
2017-12-11 13:24 ` Michael S. Tsirkin
2017-12-12 12:21 ` Wei Wang
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