mm: vmalloc: refactor vm_area_alloc_pages() function

The aim is to simplify and making the vm_area_alloc_pages()
function less confusing as it became more clogged nowadays:

- eliminate a "bulk_gfp" variable and do not overwrite a gfp
  flag for bulk allocator;
- drop __GFP_NOFAIL flag for high-order-page requests on upper
  layer. It becomes less spread between levels when it comes to
  __GFP_NOFAIL allocations;
- add a comment about a fallback path if high-order attempt is
  unsuccessful because for such cases __GFP_NOFAIL is dropped;
- fix a typo in a commit message.

Link: https://lkml.kernel.org/r/20240827190916.34242-1-urezki@gmail.comSigned-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/vmalloc.c

@@ -3515,8 +3515,6 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
 		unsigned int order, unsigned int nr_pages, struct page **pages)
 {
 	unsigned int nr_allocated = 0;
-	gfp_t alloc_gfp = gfp;
-	bool nofail = gfp & __GFP_NOFAIL;
 	struct page *page;
 	int i;
 
@@ -3527,9 +3525,6 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
 	 * more permissive.
 	 */
 	if (!order) {
-		/* bulk allocator doesn't support nofail req. officially */
-		gfp_t bulk_gfp = gfp & ~__GFP_NOFAIL;
-
 		while (nr_allocated < nr_pages) {
 			unsigned int nr, nr_pages_request;
 
@@ -3547,12 +3542,11 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
 			 * but mempolicy wants to alloc memory by interleaving.
 			 */
 			if (IS_ENABLED(CONFIG_NUMA) && nid == NUMA_NO_NODE)
-				nr = alloc_pages_bulk_array_mempolicy_noprof(bulk_gfp,
+				nr = alloc_pages_bulk_array_mempolicy_noprof(gfp,
 							nr_pages_request,
 							pages + nr_allocated);
-
 			else
-				nr = alloc_pages_bulk_array_node_noprof(bulk_gfp, nid,
+				nr = alloc_pages_bulk_array_node_noprof(gfp, nid,
 							nr_pages_request,
 							pages + nr_allocated);
 
@@ -3566,30 +3560,24 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
 			if (nr != nr_pages_request)
 				break;
 		}
-	} else if (gfp & __GFP_NOFAIL) {
-		/*
-		 * Higher order nofail allocations are really expensive and
-		 * potentially dangerous (pre-mature OOM, disruptive reclaim
-		 * and compaction etc.
-		 */
-		alloc_gfp &= ~__GFP_NOFAIL;
 	}
 
 	/* High-order pages or fallback path if "bulk" fails. */
 	while (nr_allocated < nr_pages) {
-		if (!nofail && fatal_signal_pending(current))
+		if (!(gfp & __GFP_NOFAIL) && fatal_signal_pending(current))
 			break;
 
 		if (nid == NUMA_NO_NODE)
-			page = alloc_pages_noprof(alloc_gfp, order);
+			page = alloc_pages_noprof(gfp, order);
 		else
-			page = alloc_pages_node_noprof(nid, alloc_gfp, order);
+			page = alloc_pages_node_noprof(nid, gfp, order);
+
 		if (unlikely(!page))
 			break;
 
 		/*
 		 * Higher order allocations must be able to be treated as
-		 * indepdenent small pages by callers (as they can with
+		 * independent small pages by callers (as they can with
 		 * small-page vmallocs). Some drivers do their own refcounting
 		 * on vmalloc_to_page() pages, some use page->mapping,
 		 * page->lru, etc.
@@ -3650,7 +3638,16 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
 	set_vm_area_page_order(area, page_shift - PAGE_SHIFT);
 	page_order = vm_area_page_order(area);
 
-	area->nr_pages = vm_area_alloc_pages(gfp_mask | __GFP_NOWARN,
+	/*
+	 * Higher order nofail allocations are really expensive and
+	 * potentially dangerous (pre-mature OOM, disruptive reclaim
+	 * and compaction etc.
+	 *
+	 * Please note, the __vmalloc_node_range_noprof() falls-back
+	 * to order-0 pages if high-order attempt is unsuccessful.
+	 */
+	area->nr_pages = vm_area_alloc_pages((page_order ?
+		gfp_mask & ~__GFP_NOFAIL : gfp_mask) | __GFP_NOWARN,
 		node, page_order, nr_small_pages, area->pages);
 
 	atomic_long_add(area->nr_pages, &nr_vmalloc_pages);