mm/vmalloc: do not warn on -ENOMEM from va_alloc()

Since vmalloc() accepts non-blocking GFP flags, allocation requests may
fail when callers pass restrictive GFP masks.

va_clip() may return -ENOMEM when its GFP_NOWAIT fallback allocation fails
during NE_FIT_TYPE splitting.  This is an expected failure, so va_alloc()
should return the error without triggering a kernel splat.

Link: https://lore.kernel.org/[email protected]
Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>
Reported-by: [email protected]
Closes: https://lore.kernel.org/[email protected]
Reviewed-by: Anshuman Khandual <[email protected]>
Reviewed-by: Baoquan He <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

mm/vmalloc.c

@@ -1840,8 +1840,10 @@ va_alloc(struct vmap_area *va,
 
 	/* Update the free vmap_area. */
 	ret = va_clip(root, head, va, nva_start_addr, size);
-	if (WARN_ON_ONCE(ret))
+	if (ret) {
+		WARN_ON_ONCE(ret != -ENOMEM);
 		return ret;
+	}
 
 	return nva_start_addr;
 }
@@ -1914,12 +1916,9 @@ preload_this_cpu_lock(spinlock_t *lock, gfp_t gfp_mask, int node)
 
 	/*
 	 * Preload this CPU with one extra vmap_area object. It is used
-	 * when fit type of free area is NE_FIT_TYPE. It guarantees that
-	 * a CPU that does an allocation is preloaded.
-	 *
-	 * We do it in non-atomic context, thus it allows us to use more
-	 * permissive allocation masks to be more stable under low memory
-	 * condition and high memory pressure.
+	 * when fit type of free area is NE_FIT_TYPE. It is best effort
+	 * pre-loading. If it fails va_clip() may return -ENOMEM from its
+	 * GFP_NOWAIT fallback.
 	 */
 	if (!this_cpu_read(ne_fit_preload_node))
 		va = kmem_cache_alloc_node(vmap_area_cachep, gfp_mask, node);