Similarly to for_each_cpu_and(), introduce a for_each_cpu_and_from(),
which is handy when it's needed to traverse 2 cpumasks or bitmaps,
starting from a given position.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
 include/linux/cpumask.h | 11 +++++++++++
 include/linux/find.h    |  3 +++
 2 files changed, 14 insertions(+)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index cfb545841a2c..73ff2e0ef090 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -332,6 +332,17 @@ unsigned int __pure cpumask_next_wrap(int n, const struct cpumask *mask, int sta
 #define for_each_cpu_and(cpu, mask1, mask2)				\
 	for_each_and_bit(cpu, cpumask_bits(mask1), cpumask_bits(mask2), small_cpumask_bits)
 
+/**
+ * for_each_cpu_and_from - iterate over every cpu in both masks starting from a given cpu
+ * @cpu: the (optionally unsigned) integer iterator
+ * @mask1: the first cpumask pointer
+ * @mask2: the second cpumask pointer
+ *
+ * After the loop, cpu is >= nr_cpu_ids.
+ */
+#define for_each_cpu_and_from(cpu, mask1, mask2)				\
+	for_each_and_bit_from(cpu, cpumask_bits(mask1), cpumask_bits(mask2), small_cpumask_bits)
+
 /**
  * for_each_cpu_andnot - iterate over every cpu present in one mask, excluding
  *			 those present in another.
diff --git a/include/linux/find.h b/include/linux/find.h
index 5e4f39ef2e72..dfd3d51ff590 100644
--- a/include/linux/find.h
+++ b/include/linux/find.h
@@ -563,6 +563,9 @@ unsigned long find_next_bit_le(const void *addr, unsigned
 	     (bit) = find_next_and_bit((addr1), (addr2), (size), (bit)), (bit) < (size);\
 	     (bit)++)
 
+#define for_each_and_bit_from(bit, addr1, addr2, size) \
+	for (; (bit) = find_next_and_bit((addr1), (addr2), (size), (bit)), (bit) < (size); (bit)++)
+
 #define for_each_andnot_bit(bit, addr1, addr2, size) \
 	for ((bit) = 0;									\
 	     (bit) = find_next_andnot_bit((addr1), (addr2), (size), (bit)), (bit) < (size);\
-- 
2.40.1

On Thu,  7 Dec 2023 12:38:55 -0800 Yury Norov <yury.norov@gmail.com> wrote:

> Similarly to for_each_cpu_and(), introduce a for_each_cpu_and_from(),
> which is handy when it's needed to traverse 2 cpumasks or bitmaps,
> starting from a given position.

A naming question:

> --- a/include/linux/cpumask.h
> +++ b/include/linux/cpumask.h
> @@ -332,6 +332,17 @@ unsigned int __pure cpumask_next_wrap(int n, const struct cpumask *mask, int sta
>  #define for_each_cpu_and(cpu, mask1, mask2)				\
>  	for_each_and_bit(cpu, cpumask_bits(mask1), cpumask_bits(mask2), small_cpumask_bits)
>  
> +/**
> + * for_each_cpu_and_from - iterate over every cpu in both masks starting from a given cpu
> + * @cpu: the (optionally unsigned) integer iterator
> + * @mask1: the first cpumask pointer
> + * @mask2: the second cpumask pointer
> + *
> + * After the loop, cpu is >= nr_cpu_ids.
> + */
> +#define for_each_cpu_and_from(cpu, mask1, mask2)				\
> +	for_each_and_bit_from(cpu, cpumask_bits(mask1), cpumask_bits(mask2), small_cpumask_bits)

Shouldn't this be for_each_and_cpu_from()?  That seems more consistent
and makes a little more sense given what the iterator does.

On Thu, Dec 07, 2023 at 01:41:56PM -0800, Andrew Morton wrote:
> On Thu,  7 Dec 2023 12:38:55 -0800 Yury Norov <yury.norov@gmail.com> wrote:
> 
> > Similarly to for_each_cpu_and(), introduce a for_each_cpu_and_from(),
> > which is handy when it's needed to traverse 2 cpumasks or bitmaps,
> > starting from a given position.
> 
> A naming question:
> 
> > --- a/include/linux/cpumask.h
> > +++ b/include/linux/cpumask.h
> > @@ -332,6 +332,17 @@ unsigned int __pure cpumask_next_wrap(int n, const struct cpumask *mask, int sta
> >  #define for_each_cpu_and(cpu, mask1, mask2)				\
> >  	for_each_and_bit(cpu, cpumask_bits(mask1), cpumask_bits(mask2), small_cpumask_bits)
> >  
> > +/**
> > + * for_each_cpu_and_from - iterate over every cpu in both masks starting from a given cpu
> > + * @cpu: the (optionally unsigned) integer iterator
> > + * @mask1: the first cpumask pointer
> > + * @mask2: the second cpumask pointer
> > + *
> > + * After the loop, cpu is >= nr_cpu_ids.
> > + */
> > +#define for_each_cpu_and_from(cpu, mask1, mask2)				\
> > +	for_each_and_bit_from(cpu, cpumask_bits(mask1), cpumask_bits(mask2), small_cpumask_bits)
> 
> Shouldn't this be for_each_and_cpu_from()?  That seems more consistent
> and makes a little more sense given what the iterator does.

Maybe it should... But we already have some iterators with this type
of naming: for_each_cpu_and, for_each_cpu_andnot, for_each_cpu_or.

This naming style goes quite long back in the history. Corresponding
bitmap iterators have better naming although...