remove unused page_size fn arg + fix tests

substrate/frame/staking/src/lib.rs

@@ -1200,8 +1200,7 @@ impl<T: Config> EraInfo<T> {
 			.defensive_saturating_add((page_size as usize).defensive_saturating_sub(1))
 			.saturating_div(page_size as usize);
 
-		let (exposure_metadata, exposure_pages) =
-			exposure.into_pages::<T::MaxExposurePageSize>(page_size);
+		let (exposure_metadata, exposure_pages) = exposure.into_pages::<T::MaxExposurePageSize>();
 		defensive_assert!(exposure_pages.len() == expected_page_count, "unexpected page count");
 
 		<ErasStakersOverview<T>>::insert(era, &validator, &exposure_metadata);

substrate/frame/staking/src/tests.rs

@@ -6574,10 +6574,11 @@ fn can_page_exposure() {
 		Exposure { total: total_stake, own: own_stake, others };
 
 	// when
+	MaxExposurePageSize::set(3);
 	let (exposure_metadata, exposure_page): (
 		PagedExposureMetadata<Balance>,
 		Vec<ExposurePage<AccountId, Balance, MaxExposurePageSize>>,
-	) = exposure.clone().into_pages::<MaxExposurePageSize>(3);
+	) = exposure.clone().into_pages::<MaxExposurePageSize>();
 
 	// then
 	// 7 pages of nominators.

substrate/primitives/staking/src/lib.rs

@@ -382,15 +382,16 @@ impl<AccountId: Clone, Balance: HasCompact + AtLeast32BitUnsigned + Copy + MaxEn
 	Exposure<AccountId, Balance>
 {
 	/// Splits an `Exposure` into `PagedExposureMetadata` and multiple chunks of
-	/// `IndividualExposure` with each chunk having maximum of `page_size` elements.
+	/// `IndividualExposure` with each chunk having at least 1 element and a maximum of
+	/// `MaxExposurePageSize::get()` elements.
 	pub fn into_pages<MaxExposurePageSize>(
 		self,
-		page_size: Page,
 	) -> (PagedExposureMetadata<Balance>, Vec<ExposurePage<AccountId, Balance, MaxExposurePageSize>>)
 	where
 		MaxExposurePageSize: Get<u32>,
 	{
-		let individual_chunks = self.others.chunks(page_size as usize);
+		debug_assert!(MaxExposurePageSize::get() >= 1);
+		let individual_chunks = self.others.chunks(MaxExposurePageSize::get() as usize);
 		let mut exposure_pages: Vec<ExposurePage<AccountId, Balance, MaxExposurePageSize>> =
 			Vec::with_capacity(individual_chunks.len());