mm: reduce deferred struct page init ifdeffery

Patch series "mm: Fix several issues with unaccepted memory", v2.

The patchset addresses several issues related to unaccepted memory.

Pacth 1/7 preparatory cleanup.

Patch 2/7 ensures that __alloc_pages_bulk() will not exhaust all
accepted memory without accepting more.

Patches 3/7-5/7 are preparations for patch 6/7, which fixes
alloc_config_page() on machines with unaccepted memory.  This allows, for
example, the allocation of gigantic pages at runtime.

Patch 7/7 enables the kernel to accept memory up to the promo watermark.


This patch (of 7):

Add dummy _deferred_grow_zone() for !DEFERRED_STRUCT_PAGE_INIT and remove
#ifdefs in two places.

No functional changes.

Link: https://lkml.kernel.org/r/20240809114854.3745464-1-kirill.shutemov@linux.intel.com
Link: https://lkml.kernel.org/r/20240809114854.3745464-3-kirill.shutemov@linux.intel.comSigned-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/page_alloc.c

@@ -322,6 +322,11 @@ static inline bool deferred_pages_enabled(void)
 {
 	return false;
 }
+
+static inline bool _deferred_grow_zone(struct zone *zone, unsigned int order)
+{
+	return false;
+}
 #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
 
 /* Return a pointer to the bitmap storing bits affecting a block of pages */
@@ -3395,7 +3400,6 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
 			if (cond_accept_memory(zone, order))
 				goto try_this_zone;
 
-#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 			/*
 			 * Watermark failed for this zone, but see if we can
 			 * grow this zone if it contains deferred pages.
@@ -3404,7 +3408,6 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
 				if (_deferred_grow_zone(zone, order))
 					goto try_this_zone;
 			}
-#endif
 			/* Checked here to keep the fast path fast */
 			BUILD_BUG_ON(ALLOC_NO_WATERMARKS < NR_WMARK);
 			if (alloc_flags & ALLOC_NO_WATERMARKS)
@@ -3450,13 +3453,11 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
 			if (cond_accept_memory(zone, order))
 				goto try_this_zone;
 
-#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 			/* Try again if zone has deferred pages */
 			if (deferred_pages_enabled()) {
 				if (_deferred_grow_zone(zone, order))
 					goto try_this_zone;
 			}
-#endif
 		}
 	}