Now we can simplify code that allocates cpumasks for local needs.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Similarly to cpumask_weight_and(), cpumask_weight_andnot() is a handy
helper that may help to avoid creating an intermediate mask just to
calculate number of bits that set in a 1st given mask, and clear in 2nd
one.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Clean up some punctutation and abbreviations.
Add kernel-doc notation for one function and function return value
for 39 functions.

cpumask.h:
Fix some punctuation (plural vs. possessive).
Fix some abbreviations (ie. -> i.e., id -> ID).

Fix 35 warnings like this:
include/linux/cpumask.h:161: warning: No description found for return value of 'cpumask_first'

cpumask.c:
Add Return: value for 4 functions.
Add kernel-doc for cpumask_any_distribute().

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>

Update lib/cpumask.c and <linux/cpumask.h> to fix all kernel-doc
warnings:

include/linux/cpumask.h:185: warning: Function parameter or member 'srcp1' not described in 'cpumask_first_and'
include/linux/cpumask.h:185: warning: Function parameter or member 'srcp2' not described in 'cpumask_first_and'
include/linux/cpumask.h:185: warning: Excess function parameter 'src1p' description in 'cpumask_first_and'
include/linux/cpumask.h:185: warning: Excess function parameter 'src2p' description in 'cpumask_first_and'

lib/cpumask.c:59: warning: Function parameter or member 'node' not described in 'alloc_cpumask_var_node'
lib/cpumask.c:169: warning: Function parameter or member 'src1p' not described in 'cpumask_any_and_distribute'
lib/cpumask.c:169: warning: Function parameter or member 'src2p' not described in 'cpumask_any_and_distribute'

Fixes: 7b4967c53204 ("cpumask: Add alloc_cpumask_var_node()")
Fixes: 839cad5fa54b ("cpumask: fix function description kernel-doc notation")
Fixes: 93ba139ba819 ("cpumask: use find_first_and_bit()")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>

Now that we have raw_atomic*_<op>() definitions, there's no need to use
arch_atomic*_<op>() definitions outside of the low-level atomic
definitions.

Move treewide users of arch_atomic*_<op>() over to the equivalent
raw_atomic*_<op>().

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230605070124.3741859-19-mark.rutland@arm.com

Pull xfs percpu counter fixes from Darrick Wong:
 "We discovered a filesystem summary counter corruption problem that was
  traced to cpu hot-remove racing with the call to percpu_counter_sum
  that sets the free block count in the superblock when writing it to
  disk. The root cause is that percpu_counter_sum doesn't cull from
  dying cpus and hence misses those counter values if the cpu shutdown
  hooks have not yet run to merge the values.

  I'm hoping this is a fairly painless fix to the problem, since the
  dying cpu mask should generally be empty. It's been in for-next for a
  week without any complaints from the bots.

   - Fix a race in the percpu counters summation code where the
     summation failed to add in the values for any CPUs that were dying
     but not yet dead. This fixes some minor discrepancies and incorrect
     assertions when running generic/650"

* tag 'xfs-6.3-fixes-4' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  pcpcntr: remove percpu_counter_sum_all()
  fork: remove use of percpu_counter_sum_all
  pcpcntrs: fix dying cpu summation race
  cpumask: introduce for_each_cpu_or

Equivalent of for_each_cpu_and, except it ORs the two masks together
so it iterates all the CPUs present in either mask.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

The cpumask_check() was unnecessarily tight, and causes problems for the
users of cpumask_next().

We have a number of users that take the previous return value of one of
the bit scanning functions and subtract one to keep it in "range".  But
since the scanning functions end up returning up to 'small_cpumask_bits'
instead of the tighter 'nr_cpumask_bits', the range really needs to be
using that widened form.

[ This "previous-1" behavior is also the reason we have all those
  comments about /* -1 is a legal arg here. */ and separate checks for
  that being ok.  So we could have just made "small_cpumask_bits-1"
  be a similar special "don't check this" value.

  Tetsuo Handa even suggested a patch that only does that for
  cpumask_next(), since that seems to be the only actual case that
  triggers, but that all makes it even _more_ magical and special. So
  just relax the check ]

One example of this kind of pattern being the 'c_start()' function in
arch/x86/kernel/cpu/proc.c, but also duplicated in various forms on
other architectures.

Reported-by: syzbot+96cae094d90877641f32@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=96cae094d90877641f32
Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Link: https://lore.kernel.org/lkml/c1f4cc16-feea-b83c-82cf-1a1f007b7eb9@I-love.SAKURA.ne.jp/
Fixes: 596ff4a09b89 ("cpumask: re-introduce constant-sized cpumask optimizations")
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Commit 596ff4a09b89 ("cpumask: re-introduce constant-sized cpumask
optimizations") changed cpumask_setall() to use "bitmap_set()" instead
of "bitmap_fill()", because bitmap_fill() would explicitly set all the
bits of a constant sized small bitmap, and that's exactly what we don't
want: we want to only set bits up to 'nr_cpu_ids', which is what
"bitmap_set()" does.

However, Yury correctly points out that while "bitmap_set()" does indeed
only set bits up to the required bitmap size, it doesn't _clear_ bits
above that size, so the upper bits would still not have well-defined
values.

Now, none of this should really matter, since any bits set past
'nr_cpu_ids' should always be ignored in the first place.  Yes, the bit
scanning functions might return them as a result, but since users should
always consider the ">= nr_cpu_ids" condition to mean "no more bits",
that shouldn't have any actual effect (see previous commit 8ca09d5fa354
"cpumask: fix incorrect cpumask scanning result checks").

But let's just do it right, the way the code was _intended_ to work.  We
have had enough lazy code that works but bites us in the *rse later
(again, see previous commit) that there's no reason to not just do this
properly.

It turns out that "bitmap_fill()" gets this all right for the complex
case, and really only fails for the inlined optimized case that just
fills the whole word.  And while we could just fix bitmap_fill() to use
the proper last word mask, there's two issues with that:

 - the cpumask case wants to do the _optimization_ based on "NR_CPUS is
   a small constant", but then wants to do the actual bit _fill_ based
   on "nr_cpu_ids" that isn't necessarily that same constant

 - we have lots of non-cpumask users of bitmap_fill(), and while they
   hopefully don't care, and probably would want the proper semantics
   anyway ("only set bits up to the limit"), I do not want the cpumask
   changes to impact other parts

So this ends up just doing the single-word optimization by hand in the
cpumask code.  If our cpumask is fundamentally limited to a single word,
just do the proper "fill in that word" exactly.  And if it's the more
complex multi-word case, then the generic bitmap_fill() will DTRT.

This is all an example of how our bitmap function optimizations really
are somewhat broken.  They conflate the "this is size of the bitmap"
optimizations with the actual bit(s) we want to set.

In many cases we really want to have the two be separate things:
sometimes we base our optimizations on the size of the whole bitmap ("I
know this whole bitmap fits in a single word, so I'll just use
single-word accesses"), and sometimes we base them on the bit we are
looking at ("this is just acting on bits that are in the first word, so
I'll use single-word accesses").

Notice how the end result of the two optimizations are the same, but the
way we get to them are quite different.

And all our cpumask optimization games are really about that fundamental
distinction, and we'd often really want to pass in both the "this is the
bit I'm working on" (which _can_ be a small constant but might be
variable), and "I know it's in this range even if it's variable" (based
on CONFIG_NR_CPUS).

So this cpumask_setall() implementation just makes that explicit.  It
checks the "I statically know the size is small" using the known static
size of the cpumask (which is what that 'small_cpumask_bits' is all
about), but then sets the actual bits using the exact number of cpus we
have (ie 'nr_cpumask_bits')

Of course, in a perfect world, the compiler would have done all the
range analysis (possibly with help from us just telling it that
"this value is always in this range"), and would do all of this for us.
But that is not the world we live in.

While we dream of that perfect world, this does that manual logic to
make it all work out.  And this was a very long explanation for a small
code change that shouldn't even matter.

Reported-by: Yury Norov <yury.norov@gmail.com>
Link: https://lore.kernel.org/lkml/ZAV9nGG9e1%2FrV+L%2F@yury-laptop/
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The never used nr_cpumask_size is just a typo, hence use existing
redefinition that's called nr_cpumask_bits.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>