linux-kernel - [PATCH 4/4] mm: kvrealloc: properly document __GFP

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Message-ID: <20240730185049.6244-5-dakr@kernel.org>
Date: Tue, 30 Jul 2024 20:49:44 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: akpm@...ux-foundation.org,
	urezki@...il.com,
	hch@...radead.org,
	vbabka@...e.cz
Cc: mhocko@...e.com,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	Danilo Krummrich <dakr@...nel.org>
Subject: [PATCH 4/4] mm: kvrealloc: 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.

Signed-off-by: Danilo Krummrich <dakr@...nel.org>
---
 mm/util.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/mm/util.c b/mm/util.c
index bfb2d69b6434..f899b0f984a0 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -726,12 +726,17 @@ EXPORT_SYMBOL(kvfree_sensitive);
  * @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, kvrealloc() behaves exactly like kvmalloc(). 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 kvfree() for the
  * same memory allocation.
  *
-- 
2.45.2