In most real-life cases, 0-length bitmap provided by user is a sign of
an error. The API doesn't provide any guarantees on returned value, and
the bitmap pointers are not dereferenced.

Signed-off-by: Yury Norov <ynorov@nvidia.com>

Bitmap API handles nbits == 0 in most cases correctly, i.e. it doesn't
dereferene underlying bitmap and returns a sane value where convenient,
or implementation defined, or undef.

Implicitly testing nbits == 0 case, however, may make an impression that
this is a regular case. This is wrong. In most cases nbits == 0 is a
sign of an error on a client side. The tests should not make such an
implression.

This patch reworks the existing tests to not test nbits == 0. The
following patch adds an explicit test for it with an appropriate
precaution.

Signed-off-by: Yury Norov <ynorov@nvidia.com>

Test the function for correctness when some bits are set in the last word
of bitmap beyond nbits. This is motivated by commit a9dadc1c512807f9
("powerpc/xive: Fix the size of the cpumask used in
xive_find_target_in_mask()").

Signed-off-by: Yury Norov <ynorov@nvidia.com>

The function calculates a Hamming weight of a bitmap starting from an
arbitrary bit.

Signed-off-by: Yury Norov <ynorov@nvidia.com>

Different subtests print output in slightly different formats. Unify the
format for better visual representation.

The test output before:

[    0.553474] test_bitmap: parselist: 14: input is '0-2047:128/256' OK, Time: 202
[    0.555121] test_bitmap: bitmap_print_to_pagebuf: input is '0-32767
[    0.555121] ', Time: 1278
[    0.578392] test_bitmap: Time spent in test_bitmap_read_perf:	427864
[    0.580137] test_bitmap: Time spent in test_bitmap_write_perf:	793554
[    0.581957] test_bitmap: all 390447 tests passed

And after:

[    0.314982] test_bitmap: parselist('0-2047:128/256'):	135
[    0.315517] test_bitmap: scnprintf("%*pbl", '0-32767'):	342
[    0.330045] test_bitmap: test_bitmap_read_perf:		252294
[    0.331132] test_bitmap: test_bitmap_write_perf:		539001
[    0.332163] test_bitmap: all 390447 tests passed

Signed-off-by: Yury Norov <ynorov@nvidia.com>

scnprintf("%*pbl") is more verbose than bitmap_print_to_pagebuf().
Switch the test to using it. This also improves the test output
because bitmap_print_to_pagebuf() adds \n at the end of the printed
bitmap, which breaks the test format.

Signed-off-by: Yury Norov <ynorov@nvidia.com>

Make sure that bitmap_scatter() and bitmap_gather() do not modify
the bits outside of the given nbits span.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Yury Norov <ynorov@nvidia.com>

This has been unused since commit 3aa56885e516 ("bitmap: replace
bitmap_{from,to}_u32array") in 2018.

Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>

make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in lib/find_bit_benchmark.o
WARNING: modpost: missing MODULE_DESCRIPTION() in lib/cpumask_kunit.o
WARNING: modpost: missing MODULE_DESCRIPTION() in lib/test_bitmap.o

Add the missing invocations of the MODULE_DESCRIPTION() macro.

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>

Pull bitmap updates from Yury Norov:

 - topology_span_sane() optimization from Kyle Meyer

 - fns() rework from Kuan-Wei Chiu (used in cpumask_local_spread() and
   other places)

 - headers cleanup from Andy

 - add a MAINTAINERS record for bitops API

* tag 'bitmap-for-6.10v2' of https://github.com/norov/linux:
  usercopy: Don't use "proxy" headers
  bitops: Move aligned_byte_mask() to wordpart.h
  MAINTAINERS: add BITOPS API record
  bitmap: relax find_nth_bit() limitation on return value
  lib: make test_bitops compilable into the kernel image
  bitops: Optimize fns() for improved performance
  lib/test_bitops: Add benchmark test for fns()
  Compiler Attributes: Add __always_used macro
  sched/topology: Optimize topology_span_sane()
  cpumask: Add for_each_cpu_from()