[dhowells-fs:netfs-crypt 37/42] fs/netfs/direct_read.c:86:20: warning: variable 'len' is uninitialized when used here

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

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git netfs-crypt
head:   ae7ccdf83025020c44837849de26fb4546fbf825
commit: e7c8280c95acfbbef1fc569cbb950835ab68c7f2 [37/42] netfs: Implement bounce-buffering for unbuffered/DIO read
config: x86_64-kexec (https://download.01.org/0day-ci/archive/20260323/202603232150.smRruVIF-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260323/202603232150.smRruVIF-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/202603232150.smRruVIF-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> fs/netfs/direct_read.c:86:20: warning: variable 'len' is uninitialized when used here [-Wuninitialized]
      86 |                 len = round_down(len, rreq->crypto_bsize);
         |                                  ^~~
   include/linux/math.h:35:28: note: expanded from macro 'round_down'
      35 | #define round_down(x, y) ((x) & ~__round_mask(x, y))
         |                            ^
   fs/netfs/direct_read.c:74:12: note: initialize the variable 'len' to silence this warning
      74 |         size_t len;
         |                   ^
         |                    = 0
   1 warning generated.


vim +/len +86 fs/netfs/direct_read.c

    64	
    65	/*
    66	 * Prepare the buffer for the read RPC.  Limits are applied and the buffer may
    67	 * be rounded down.  Bounce bufferage will be added if necessary.
    68	 */
    69	int netfs_prepare_unbuffered_read_buffer(struct netfs_io_subrequest *subreq,
    70						 unsigned int max_segs)
    71	{
    72		struct netfs_io_request *rreq = subreq->rreq;
    73		struct netfs_io_stream *stream = &rreq->io_streams[0];
    74		size_t len;
    75		int ret;
    76	
    77		bvecq_pos_set(&subreq->dispatch_pos, &stream->dispatch_cursor);
    78		bvecq_pos_set(&subreq->content, &stream->dispatch_cursor);
    79	
    80		/* Limit encrypted reads so that we don't split an encryption block
    81		 * across two subrequests unless the filesystem doesn't support blocks
    82		 * that big.
    83		 */
    84		if (subreq->len > rreq->crypto_bsize &&
    85		    test_bit(NETFS_RREQ_CONTENT_ENCRYPTION, &rreq->flags)) {
  > 86			len = round_down(len, rreq->crypto_bsize);
    87			if (WARN_ON_ONCE(len == 0))
    88				return -EIO;
    89		}
    90	
    91		/* Expand the bounce buffer so that we've got something to read into. */
    92		if (test_bit(NETFS_RREQ_USE_BOUNCE_BUFFER, &rreq->flags)) {
    93			ret = bvecq_buffer_add_space(&rreq->bounce_cursor,
    94						     &rreq->bounce_alloc_to,
    95						     subreq->start + subreq->len,
    96						     round_up(rreq->start + rreq->len,
    97							      rreq->crypto_bsize),
    98						     false, GFP_KERNEL);
    99			if (ret < 0)
   100				return ret;
   101		}
   102	
   103		len = bvecq_slice(&stream->dispatch_cursor, subreq->len, max_segs,
   104				  &subreq->nr_segs);
   105	
   106		if (len < subreq->len) {
   107			subreq->len = len;
   108			trace_netfs_sreq(subreq, netfs_sreq_trace_limited);
   109		}
   110	
   111		stream->buffered   -= subreq->len;
   112		stream->issue_from += subreq->len;
   113		return 0;
   114	}
   115	

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