From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Wang, Wei W" Subject: RE: [PATCH v18 05/10] xbitmap: add more operations Date: Fri, 1 Dec 2017 15:09:08 +0000 Message-ID: <286AC319A985734F985F78AFA26841F739376DA1__47943.4458110065$1512140962$gmane$org@shsmsx102.ccr.corp.intel.com> References: <1511963726-34070-1-git-send-email-wei.w.wang@intel.com> <1511963726-34070-6-git-send-email-wei.w.wang@intel.com> <201711301934.CDC21800.FSLtJFFOOVQHMO@I-love.SAKURA.ne.jp> <5A210C96.8050208@intel.com> <201712012202.BDE13557.MJFQLtOOHVOFSF@I-love.SAKURA.ne.jp> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <201712012202.BDE13557.MJFQLtOOHVOFSF@I-love.SAKURA.ne.jp> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Tetsuo Handa Cc: "yang.zhang.wz@gmail.com" , "kvm@vger.kernel.org" , "mst@redhat.com" , "liliang.opensource@gmail.com" , "qemu-devel@nongnu.org" , "virtualization@lists.linux-foundation.org" , "linux-mm@kvack.org" , "aarcange@redhat.com" , "virtio-dev@lists.oasis-open.org" , "mawilcox@microsoft.com" , "willy@infradead.org" , "quan.xu@aliyun.com" , "nilal@redhat.com" , "riel@redhat.com" , "cornelia.huck@de.ibm.com" , "mhocko@kernel.org" , "linux-kernel@vger.kernel.org" , amit.shah@red List-Id: virtualization@lists.linuxfoundation.org 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