linux-kernel - [kbusch:dma-prereg-v6 6/6] drivers/nvme/host/pci.c:1935:7: warning: variable 'pages

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Date:   Sun, 14 Aug 2022 00:53:18 +0800
From:   kernel test robot <lkp@...el.com>
To:     Keith Busch <kbusch@...nel.org>
Cc:     llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org
Subject: [kbusch:dma-prereg-v6 6/6] drivers/nvme/host/pci.c:1935:7: warning:
 variable 'pages_per' set but not used

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/kbusch/linux.git dma-prereg-v6
head:   cdcec28a049590800a8726d83b7e635527204a26
commit: cdcec28a049590800a8726d83b7e635527204a26 [6/6] nvme-pci: implement dma_map support
config: i386-randconfig-a013 (https://download.01.org/0day-ci/archive/20220814/202208140037.VHIG9r0t-lkp@intel.com/config)
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 3329cec2f79185bafd678f310fafadba2a8c76d2)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://git.kernel.org/pub/scm/linux/kernel/git/kbusch/linux.git/commit/?id=cdcec28a049590800a8726d83b7e635527204a26
        git remote add kbusch https://git.kernel.org/pub/scm/linux/kernel/git/kbusch/linux.git
        git fetch --no-tags kbusch dma-prereg-v6
        git checkout cdcec28a049590800a8726d83b7e635527204a26
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 SHELL=/bin/bash drivers/nvme/host/

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@...el.com>

All warnings (new ones prefixed by >>):

   drivers/nvme/host/pci.c:967:7: warning: variable 'nprps_left' is uninitialized when used here [-Wuninitialized]
                   if (nprps_left <= last_prp + 1) {
                       ^~~~~~~~~~
   drivers/nvme/host/pci.c:893:49: note: initialize the variable 'nprps_left' to silence this warning
           int index, offset, i, length, nprps, nprps_left;
                                                          ^
                                                           = 0
>> drivers/nvme/host/pci.c:1935:7: warning: variable 'pages_per' set but not used [-Wunused-but-set-variable]
                   int pages_per = nvme_pages;
                       ^
   2 warnings generated.


vim +/pages_per +1935 drivers/nvme/host/pci.c

  1905	
  1906	#ifdef CONFIG_HAS_DMA
  1907	/*
  1908	 * Important: bvec must be describing a virtually contiguous buffer.
  1909	 */
  1910	static void *nvme_pci_dma_map(struct request_queue *q,
  1911				       struct bio_vec *bvec, int nr_vecs)
  1912	{
  1913		const int nvme_pages = 1 << (PAGE_SIZE - NVME_CTRL_PAGE_SIZE);
  1914		struct nvme_ns *ns = q->queuedata;
  1915		struct nvme_dev *dev = to_nvme_dev(ns->ctrl);
  1916		struct nvme_dma_mapping *mapping;
  1917		int i, j, k, size, ret = -ENOMEM;
  1918	
  1919		if (!nr_vecs)
  1920			return ERR_PTR(-EINVAL);
  1921	
  1922		mapping = kzalloc(sizeof(*mapping), GFP_KERNEL);
  1923		if (!mapping)
  1924			return ERR_PTR(-ENOMEM);
  1925	
  1926		mapping->nr_pages = nr_vecs * nvme_pages;
  1927		size = sizeof(*mapping->prps) * mapping->nr_pages;
  1928		mapping->prps = dma_alloc_coherent(dev->dev, size,
  1929					&mapping->prp_dma_addr, GFP_KERNEL);
  1930		if (!mapping->prps)
  1931			goto free_mapping;
  1932	
  1933		for (i = 0, k = 0; i < nr_vecs; i++) {
  1934			struct bio_vec *bv = bvec + i;
> 1935			int pages_per = nvme_pages;
  1936			dma_addr_t dma_addr;
  1937	
  1938			if (i == 0) {
  1939				mapping->offset = bv->bv_offset;
  1940				pages_per -= mapping->offset >> NVME_CTRL_PAGE_SHIFT;
  1941			} else if (bv->bv_offset) {
  1942				ret = -EINVAL;
  1943				goto err;
  1944			}
  1945	
  1946			if (bv->bv_offset + bv->bv_len != PAGE_SIZE &&
  1947			    i < nr_vecs - 1) {
  1948				ret = -EINVAL;
  1949				goto err;
  1950			}
  1951	
  1952			dma_addr = dma_map_bvec(dev->dev, bv, 0, 0);
  1953			if (dma_mapping_error(dev->dev, dma_addr)) {
  1954				ret = -EIO;
  1955				goto err;
  1956			}
  1957	
  1958			if (i == 0)
  1959				dma_addr -= mapping->offset;
  1960	
  1961			for (j = 0; j < nvme_pages; j++)
  1962				mapping->prps[k++] = cpu_to_le64(dma_addr +
  1963							j * NVME_CTRL_PAGE_SIZE);
  1964		}
  1965	
  1966		get_device(dev->dev);
  1967		return mapping;
  1968	
  1969	err:
  1970		for (i = 0; i < k; i += nvme_pages) {
  1971			__u64 dma_addr = le64_to_cpu(mapping->prps[i]);
  1972	
  1973			dma_unmap_page(dev->dev, dma_addr,
  1974				       PAGE_SIZE - offset_in_page(dma_addr), 0);
  1975		}
  1976	
  1977		dma_free_coherent(dev->dev, size, (void *)mapping->prps,
  1978				  mapping->prp_dma_addr);
  1979	free_mapping:
  1980		kfree(mapping);
  1981		return ERR_PTR(ret);
  1982	}
  1983	

-- 
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