mempool: factor out a mempool_adjust_gfp helper

Add a helper to better isolate and document the gfp flags adjustments.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://patch.msgid.link/20251113084022.1255121-6-hch@lst.de
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Author: Christoph Hellwig

mm/mempool.c

@@ -380,6 +380,19 @@ int mempool_resize(mempool_t *pool, int new_min_nr)
 }
 EXPORT_SYMBOL(mempool_resize);
 
+/*
+ * Adjust the gfp flags for mempool allocations, as we never want to dip into
+ * the global emergency reserves or retry in the page allocator.
+ *
+ * The first pass also doesn't want to go reclaim, but the next passes do, so
+ * return a separate subset for that first iteration.
+ */
+static inline gfp_t mempool_adjust_gfp(gfp_t *gfp_mask)
+{
+	*gfp_mask |= __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
+	return *gfp_mask & ~(__GFP_DIRECT_RECLAIM | __GFP_IO);
+}
+
 /**
  * mempool_alloc - allocate an element from a memory pool
  * @pool:	pointer to the memory pool
@@ -398,20 +411,14 @@ EXPORT_SYMBOL(mempool_resize);
  */
 void *mempool_alloc_noprof(mempool_t *pool, gfp_t gfp_mask)
 {
+	gfp_t gfp_temp = mempool_adjust_gfp(&gfp_mask);
 	void *element;
 	unsigned long flags;
 	wait_queue_entry_t wait;
-	gfp_t gfp_temp;
 
 	VM_WARN_ON_ONCE(gfp_mask & __GFP_ZERO);
 	might_alloc(gfp_mask);
 
-	gfp_mask |= __GFP_NOMEMALLOC;	/* don't allocate emergency reserves */
-	gfp_mask |= __GFP_NORETRY;	/* don't loop in __alloc_pages */
-	gfp_mask |= __GFP_NOWARN;	/* failures are OK */
-
-	gfp_temp = gfp_mask & ~(__GFP_DIRECT_RECLAIM|__GFP_IO);
-
 repeat_alloc:
 	if (should_fail_ex(&fail_mempool_alloc, 1, FAULT_NOWARN)) {
 		pr_info("forcing mempool usage for %pS\n",