mm: vrealloc: properly document __GFP_ZERO behavior

Properly document that if __GFP_ZERO logic is requested, callers must
ensure that, starting with the initial memory allocation, every subsequent
call to this API for the same memory allocation is flagged with
__GFP_ZERO.  Otherwise, it is possible that __GFP_ZERO is not fully
honored by this API.

Link: https://lkml.kernel.org/r/20240730185049.6244-4-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 4339c56be3c81e4e15549eb8e42d4beb529a6247..c63f74bf2e7a664ef75ed840d8df40c385a0a143 100644 (file)
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -4036,12 +4036,17 @@ EXPORT_SYMBOL(vzalloc_node_noprof);
  * @size: the size to reallocate
  * @flags: the flags for the page level allocator
  *
- * The contents of the object pointed to are preserved up to the lesser of the
- * new and old size (__GFP_ZERO flag is effectively ignored).
- *
  * If @p is %NULL, vrealloc() behaves exactly like vmalloc(). If @size is 0 and
  * @p is not a %NULL pointer, the object pointed to is freed.
  *
+ * If __GFP_ZERO logic is requested, callers must ensure that, starting with the
+ * initial memory allocation, every subsequent call to this API for the same
+ * memory allocation is flagged with __GFP_ZERO. Otherwise, it is possible that
+ * __GFP_ZERO is not fully honored by this API.
+ *
+ * In any case, the contents of the object pointed to are preserved up to the
+ * lesser of the new and old sizes.
+ *
  * This function must not be called concurrently with itself or vfree() for the
  * same memory allocation.
  *