Revert "mm/page_alloc: Optimize free_contig_range()"

This reverts commit 8214813.

Signed-off-by: Eric Naim <dnaim@cachyos.org>

Author: 1Naim

include/linux/gfp.h

@@ -464,8 +464,6 @@ void free_contig_frozen_range(unsigned long pfn, unsigned long nr_pages);
 void free_contig_range(unsigned long pfn, unsigned long nr_pages);
 #endif
 
-void __free_contig_range(unsigned long pfn, unsigned long nr_pages);
-
 DEFINE_FREE(free_page, void *, free_page((unsigned long)_T))
 
 #endif /* __LINUX_GFP_H */

mm/page_alloc.c

@@ -90,9 +90,6 @@ typedef int __bitwise fpi_t;
 /* Free the page without taking locks. Rely on trylock only. */
 #define FPI_TRYLOCK		((__force fpi_t)BIT(2))
 
-/* free_pages_prepare() has already been called for page(s) being freed. */
-#define FPI_PREPARED		((__force fpi_t)BIT(3))
-
 /* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
 static DEFINE_MUTEX(pcp_batch_high_lock);
 #define MIN_PERCPU_PAGELIST_HIGH_FRACTION (8)
@@ -1351,9 +1348,6 @@ __always_inline bool __free_pages_prepare(struct page *page,
 	bool compound = PageCompound(page);
 	struct folio *folio = page_folio(page);
 
-	if (fpi_flags & FPI_PREPARED)
-		return true;
-
 	VM_BUG_ON_PAGE(PageTail(page), page);
 
 	trace_mm_page_free(page, order);
@@ -6830,100 +6824,6 @@ void __init page_alloc_sysctl_init(void)
 	register_sysctl_init("vm", page_alloc_sysctl_table);
 }
 
-static void free_prepared_contig_range(struct page *page,
-				       unsigned long nr_pages)
-{
-	while (nr_pages) {
-		unsigned int order;
-		unsigned long pfn;
-
-		pfn = page_to_pfn(page);
-		/* We are limited by the largest buddy order. */
-		order = pfn ? __ffs(pfn) : MAX_PAGE_ORDER;
-		/* Don't exceed the number of pages to free. */
-		order = min_t(unsigned int, order, ilog2(nr_pages));
-		order = min_t(unsigned int, order, MAX_PAGE_ORDER);
-
-		/*
-		 * Free the chunk as a single block. Our caller has already
-		 * called free_pages_prepare() for each order-0 page.
-		 */
-		__free_frozen_pages(page, order, FPI_PREPARED);
-
-		page += 1UL << order;
-		nr_pages -= 1UL << order;
-	}
-}
-
-static void __free_contig_range_common(unsigned long pfn, unsigned long nr_pages,
-				       bool is_frozen)
-{
-	struct page *page = pfn_to_page(pfn);
-	struct page *start = NULL;
-	unsigned long start_sec;
-	bool can_free = true;
-	unsigned long i;
-
-	/*
-	 * Contiguous PFNs might not have a contiguous "struct pages" in some
-	 * kernel config. Therefore, check memdesc_section(), and stop batching
-	 * once it changes, see num_pages_contiguous().
-	 */
-	for (i = 0; i < nr_pages; i++, page++) {
-		VM_WARN_ON_ONCE(PageHead(page));
-		VM_WARN_ON_ONCE(PageTail(page));
-
-		if (!is_frozen)
-			can_free = put_page_testzero(page);
-
-		if (can_free)
-			can_free = free_pages_prepare(page, 0);
-
-		if (!can_free) {
-			if (start) {
-				free_prepared_contig_range(start, page - start);
-				start = NULL;
-			}
-			continue;
-		}
-
-		if (start && memdesc_section(page->flags) != start_sec) {
-			free_prepared_contig_range(start, page - start);
-			start = page;
-			start_sec = memdesc_section(page->flags);
-		} else if (!start) {
-			start = page;
-			start_sec = memdesc_section(page->flags);
-		}
-	}
-
-	if (start)
-		free_prepared_contig_range(start, page - start);
-}
-
-/**
- * __free_contig_range - Free contiguous range of order-0 pages.
- * @pfn: Page frame number of the first page in the range.
- * @nr_pages: Number of pages to free.
- *
- * For each order-0 struct page in the physically contiguous range, put a
- * reference. Free any page who's reference count falls to zero. The
- * implementation is functionally equivalent to, but significantly faster than
- * calling __free_page() for each struct page in a loop.
- *
- * Memory allocated with alloc_pages(order>=1) then subsequently split to
- * order-0 with split_page() is an example of appropriate contiguous pages that
- * can be freed with this API.
- *
- * Context: May be called in interrupt context or while holding a normal
- * spinlock, but not in NMI context or while holding a raw spinlock.
- */
-void __free_contig_range(unsigned long pfn, unsigned long nr_pages)
-{
-	__free_contig_range_common(pfn, nr_pages, false);
-}
-EXPORT_SYMBOL(__free_contig_range);
-
 #ifdef CONFIG_CONTIG_ALLOC
 /* Usage: See admin-guide/dynamic-debug-howto.rst */
 static void alloc_contig_dump_pages(struct list_head *page_list)
@@ -7469,7 +7369,8 @@ void free_contig_range(unsigned long pfn, unsigned long nr_pages)
 	if (WARN_ON_ONCE(PageHead(pfn_to_page(pfn))))
 		return;
 
-	__free_contig_range(pfn, nr_pages);
+	for (; nr_pages--; pfn++)
+		__free_page(pfn_to_page(pfn));
 }
 EXPORT_SYMBOL(free_contig_range);
 #endif /* CONFIG_CONTIG_ALLOC */