Re: [PATCH v14 07/11] nvme: add copy offload support

[kernel test robot <lkp@intel.com>]

Hi Nitesh,

kernel test robot noticed the following build warnings:

[auto build test WARNING on f7dc24b3413851109c4047b22997bd0d95ed52a2]

url:    https://github.com/intel-lab-lkp/linux/commits/Nitesh-Shetty/block-Introduce-queue-limits-and-sysfs-for-copy-offload-support/20230811-192259
base:   f7dc24b3413851109c4047b22997bd0d95ed52a2
patch link:    https://lore.kernel.org/r/20230811105300.15889-8-nj.shetty%40samsung.com
patch subject: [PATCH v14 07/11] nvme: add copy offload support
config: arm64-randconfig-r013-20230812 (https://download.01.org/0day-ci/archive/20230812/202308120736.Od5Pc9vy-lkp@intel.com/config)
compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project.git 4a5ac14ee968ff0ad5d2cc1ffa0299048db4c88a)
reproduce: (https://download.01.org/0day-ci/archive/20230812/202308120736.Od5Pc9vy-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202308120736.Od5Pc9vy-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/nvme/host/core.c:782:2: warning: variable 'dst_lba' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
     782 |         __rq_for_each_bio(bio, req) {
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/blk-mq.h:1008:6: note: expanded from macro '__rq_for_each_bio'
    1008 |         if ((rq->bio))                  \
         |             ^~~~~~~~~
   drivers/nvme/host/core.c:804:33: note: uninitialized use occurs here
     804 |         cmnd->copy.sdlba = cpu_to_le64(dst_lba);
         |                                        ^~~~~~~
   include/linux/byteorder/generic.h:86:21: note: expanded from macro 'cpu_to_le64'
      86 | #define cpu_to_le64 __cpu_to_le64
         |                     ^
   include/uapi/linux/byteorder/little_endian.h:32:51: note: expanded from macro '__cpu_to_le64'
      32 | #define __cpu_to_le64(x) ((__force __le64)(__u64)(x))
         |                                                   ^
   drivers/nvme/host/core.c:782:2: note: remove the 'if' if its condition is always true
     782 |         __rq_for_each_bio(bio, req) {
         |         ^
   include/linux/blk-mq.h:1008:2: note: expanded from macro '__rq_for_each_bio'
    1008 |         if ((rq->bio))                  \
         |         ^
   drivers/nvme/host/core.c:772:13: note: initialize the variable 'dst_lba' to silence this warning
     772 |         u64 dst_lba, src_lba, n_lba;
         |                    ^
         |                     = 0
   1 warning generated.


vim +782 drivers/nvme/host/core.c

   765	
   766	static inline blk_status_t nvme_setup_copy_offload(struct nvme_ns *ns,
   767							   struct request *req,
   768							   struct nvme_command *cmnd)
   769	{
   770		struct nvme_copy_range *range = NULL;
   771		struct bio *bio;
   772		u64 dst_lba, src_lba, n_lba;
   773		u16 nr_range = 1, control = 0, seg = 1;
   774	
   775		if (blk_rq_nr_phys_segments(req) != COPY_MAX_SEGMENTS)
   776			return BLK_STS_IOERR;
   777	
   778		/*
   779		 * First bio contains information about source and last bio contains
   780		 * information about destination.
   781		 */
 > 782		__rq_for_each_bio(bio, req) {
   783			if (seg == blk_rq_nr_phys_segments(req)) {
   784				dst_lba = nvme_sect_to_lba(ns, bio->bi_iter.bi_sector);
   785				if (n_lba != bio->bi_iter.bi_size >> ns->lba_shift)
   786					return BLK_STS_IOERR;
   787			} else {
   788				src_lba = nvme_sect_to_lba(ns, bio->bi_iter.bi_sector);
   789				n_lba = bio->bi_iter.bi_size >> ns->lba_shift;
   790			}
   791			seg++;
   792		}
   793	
   794		if (req->cmd_flags & REQ_FUA)
   795			control |= NVME_RW_FUA;
   796	
   797		if (req->cmd_flags & REQ_FAILFAST_DEV)
   798			control |= NVME_RW_LR;
   799	
   800		memset(cmnd, 0, sizeof(*cmnd));
   801		cmnd->copy.opcode = nvme_cmd_copy;
   802		cmnd->copy.nsid = cpu_to_le32(ns->head->ns_id);
   803		cmnd->copy.control = cpu_to_le16(control);
   804		cmnd->copy.sdlba = cpu_to_le64(dst_lba);
   805		cmnd->copy.nr_range = 0;
   806	
   807		range = kmalloc_array(nr_range, sizeof(*range),
   808				      GFP_ATOMIC | __GFP_NOWARN);
   809		if (!range)
   810			return BLK_STS_RESOURCE;
   811	
   812		range[0].slba = cpu_to_le64(src_lba);
   813		range[0].nlb = cpu_to_le16(n_lba - 1);
   814	
   815		req->special_vec.bv_page = virt_to_page(range);
   816		req->special_vec.bv_offset = offset_in_page(range);
   817		req->special_vec.bv_len = sizeof(*range) * nr_range;
   818		req->rq_flags |= RQF_SPECIAL_PAYLOAD;
   819	
   820		return BLK_STS_OK;
   821	}
   822	

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