[PATCH] mm/vmalloc: Do not warn on -ENOMEM from va_alloc()

["Uladzislau Rezki (Sony)" <urezki@gmail.com>]

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.

Reported-by: syzbot+61c997e6be1d9bb300ba@syzkaller.appspotmail.com
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
---
 mm/vmalloc.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 1afca3568b9b..7a0cbba3d29d 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1817,8 +1817,10 @@ 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;
 }
@@ -1891,12 +1893,9 @@ 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);
-- 
2.47.3