[dhowells-fs:fscache-netfs-lib 1/26] lib/iov_iter.c:771:8: sparse: sparse: context imbalance in '_copy_mc_to_iter' - different lock contexts for basic block

[dhowells-fs:fscache-netfs-lib 1/26] lib/iov_iter.c:771:8: sparse: sparse: context imbalance in '_copy_mc_to_iter' - different lock contexts for basic block

[kernel test robot]

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CC: kbuild-all(a)lists.01.org
TO: David Howells <dhowells@redhat.com>

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git fscache-netfs-lib
head:   72ff7b8b0c53f453dcc5ec36195fda98dfbf605c
commit: 63173dca934066c5f100288b417834b84429045d [1/26] iov_iter: Add ITER_XARRAY
:::::: branch date: 4 hours ago
:::::: commit date: 4 days ago
config: x86_64-randconfig-s022-20210118 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
reproduce:
        # apt-get install sparse
        # sparse version: v0.6.3-208-g46a52ca4-dirty
        # https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit/?id=63173dca934066c5f100288b417834b84429045d
        git remote add dhowells-fs https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git
        git fetch --no-tags dhowells-fs fscache-netfs-lib
        git checkout 63173dca934066c5f100288b417834b84429045d
        # save the attached .config to linux build tree
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>


"sparse warnings: (new ones prefixed by >>)"
>> lib/iov_iter.c:771:8: sparse: sparse: context imbalance in '_copy_mc_to_iter' - different lock contexts for basic block

vim +/_copy_mc_to_iter +771 lib/iov_iter.c

ca146f6f091e47b3 Dan Williams  2018-07-08  747  
bf3eeb9b5f2a1a05 Dan Williams  2018-07-08  748  /**
ec6347bb43395cb9 Dan Williams  2020-10-05  749   * _copy_mc_to_iter - copy to iter with source memory error exception handling
bf3eeb9b5f2a1a05 Dan Williams  2018-07-08  750   * @addr: source kernel address
bf3eeb9b5f2a1a05 Dan Williams  2018-07-08  751   * @bytes: total transfer length
bf3eeb9b5f2a1a05 Dan Williams  2018-07-08  752   * @iter: destination iterator
bf3eeb9b5f2a1a05 Dan Williams  2018-07-08  753   *
ec6347bb43395cb9 Dan Williams  2020-10-05  754   * The pmem driver deploys this for the dax operation
ec6347bb43395cb9 Dan Williams  2020-10-05  755   * (dax_copy_to_iter()) for dax reads (bypass page-cache and the
ec6347bb43395cb9 Dan Williams  2020-10-05  756   * block-layer). Upon #MC read(2) aborts and returns EIO or the bytes
ec6347bb43395cb9 Dan Williams  2020-10-05  757   * successfully copied.
bf3eeb9b5f2a1a05 Dan Williams  2018-07-08  758   *
ec6347bb43395cb9 Dan Williams  2020-10-05  759   * The main differences between this and typical _copy_to_iter().
bf3eeb9b5f2a1a05 Dan Williams  2018-07-08  760   *
bf3eeb9b5f2a1a05 Dan Williams  2018-07-08  761   * * Typical tail/residue handling after a fault retries the copy
bf3eeb9b5f2a1a05 Dan Williams  2018-07-08  762   *   byte-by-byte until the fault happens again. Re-triggering machine
bf3eeb9b5f2a1a05 Dan Williams  2018-07-08  763   *   checks is potentially fatal so the implementation uses source
bf3eeb9b5f2a1a05 Dan Williams  2018-07-08  764   *   alignment and poison alignment assumptions to avoid re-triggering
bf3eeb9b5f2a1a05 Dan Williams  2018-07-08  765   *   hardware exceptions.
bf3eeb9b5f2a1a05 Dan Williams  2018-07-08  766   *
bf3eeb9b5f2a1a05 Dan Williams  2018-07-08  767   * * ITER_KVEC, ITER_PIPE, and ITER_BVEC can return short copies.
bf3eeb9b5f2a1a05 Dan Williams  2018-07-08  768   *   Compare to copy_to_iter() where only ITER_IOVEC attempts might return
bf3eeb9b5f2a1a05 Dan Williams  2018-07-08  769   *   a short copy.
bf3eeb9b5f2a1a05 Dan Williams  2018-07-08  770   */
ec6347bb43395cb9 Dan Williams  2020-10-05 @771  size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
8780356ef630aa57 Dan Williams  2018-05-03  772  {
8780356ef630aa57 Dan Williams  2018-05-03  773  	const char *from = addr;
8780356ef630aa57 Dan Williams  2018-05-03  774  	unsigned long rem, curr_addr, s_addr = (unsigned long) addr;
8780356ef630aa57 Dan Williams  2018-05-03  775  
00e23707442a75b4 David Howells 2018-10-22  776  	if (unlikely(iov_iter_is_pipe(i)))
ec6347bb43395cb9 Dan Williams  2020-10-05  777  		return copy_mc_pipe_to_iter(addr, bytes, i);
8780356ef630aa57 Dan Williams  2018-05-03  778  	if (iter_is_iovec(i))
8780356ef630aa57 Dan Williams  2018-05-03  779  		might_fault();
8780356ef630aa57 Dan Williams  2018-05-03  780  	iterate_and_advance(i, bytes, v,
ec6347bb43395cb9 Dan Williams  2020-10-05  781  		copyout_mc(v.iov_base, (from += v.iov_len) - v.iov_len,
ec6347bb43395cb9 Dan Williams  2020-10-05  782  			   v.iov_len),
8780356ef630aa57 Dan Williams  2018-05-03  783  		({
ec6347bb43395cb9 Dan Williams  2020-10-05  784  		rem = copy_mc_to_page(v.bv_page, v.bv_offset,
8780356ef630aa57 Dan Williams  2018-05-03  785  				      (from += v.bv_len) - v.bv_len, v.bv_len);
8780356ef630aa57 Dan Williams  2018-05-03  786  		if (rem) {
8780356ef630aa57 Dan Williams  2018-05-03  787  			curr_addr = (unsigned long) from;
8780356ef630aa57 Dan Williams  2018-05-03  788  			bytes = curr_addr - s_addr - rem;
8780356ef630aa57 Dan Williams  2018-05-03  789  			return bytes;
8780356ef630aa57 Dan Williams  2018-05-03  790  		}
8780356ef630aa57 Dan Williams  2018-05-03  791  		}),
8780356ef630aa57 Dan Williams  2018-05-03  792  		({
ec6347bb43395cb9 Dan Williams  2020-10-05  793  		rem = copy_mc_to_kernel(v.iov_base, (from += v.iov_len)
ec6347bb43395cb9 Dan Williams  2020-10-05  794  					- v.iov_len, v.iov_len);
8780356ef630aa57 Dan Williams  2018-05-03  795  		if (rem) {
8780356ef630aa57 Dan Williams  2018-05-03  796  			curr_addr = (unsigned long) from;
8780356ef630aa57 Dan Williams  2018-05-03  797  			bytes = curr_addr - s_addr - rem;
8780356ef630aa57 Dan Williams  2018-05-03  798  			return bytes;
8780356ef630aa57 Dan Williams  2018-05-03  799  		}
63173dca934066c5 David Howells 2020-02-10  800  		}),
63173dca934066c5 David Howells 2020-02-10  801  		({
63173dca934066c5 David Howells 2020-02-10  802  		rem = copy_mc_to_page(v.bv_page, v.bv_offset,
63173dca934066c5 David Howells 2020-02-10  803  				      (from += v.bv_len) - v.bv_len, v.bv_len);
63173dca934066c5 David Howells 2020-02-10  804  		if (rem) {
63173dca934066c5 David Howells 2020-02-10  805  			curr_addr = (unsigned long) from;
63173dca934066c5 David Howells 2020-02-10  806  			bytes = curr_addr - s_addr - rem;
63173dca934066c5 David Howells 2020-02-10  807  			return bytes;
63173dca934066c5 David Howells 2020-02-10  808  		}
8780356ef630aa57 Dan Williams  2018-05-03  809  		})
8780356ef630aa57 Dan Williams  2018-05-03  810  	)
8780356ef630aa57 Dan Williams  2018-05-03  811  
8780356ef630aa57 Dan Williams  2018-05-03  812  	return bytes;
8780356ef630aa57 Dan Williams  2018-05-03  813  }
ec6347bb43395cb9 Dan Williams  2020-10-05  814  EXPORT_SYMBOL_GPL(_copy_mc_to_iter);
ec6347bb43395cb9 Dan Williams  2020-10-05  815  #endif /* CONFIG_ARCH_HAS_COPY_MC */
8780356ef630aa57 Dan Williams  2018-05-03  816  

:::::: The code at line 771 was first introduced by commit
:::::: ec6347bb43395cb92126788a1a5b25302543f815 x86, powerpc: Rename memcpy_mcsafe() to copy_mc_to_{user, kernel}()

:::::: TO: Dan Williams <dan.j.williams@intel.com>
:::::: CC: Borislav Petkov <bp@suse.de>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org

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