linux-kernel - [PATCH 2/4] mm: vrealloc: consider spare memory for __GFP

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Message-ID: <20240730185049.6244-3-dakr@kernel.org>
Date: Tue, 30 Jul 2024 20:49:42 +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 2/4] mm: vrealloc: consider spare memory for __GFP_ZERO

Zero spare memory when shrinking a buffer with __GFP_ZERO.

Fixes: 1f39ee9615a8 ("mm: vmalloc: implement vrealloc()")
Signed-off-by: Danilo Krummrich <dakr@...nel.org>
---
 mm/vmalloc.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 2a6d4ce57b73..6a2fef6378e4 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -4077,12 +4077,15 @@ void *vrealloc_noprof(const void *p, size_t size, gfp_t flags)
 		old_size = get_vm_area_size(vm);
 	}
 
+	/*
+	 * TODO: Shrink the vm_area, i.e. unmap and free unused pages. What
+	 * would be a good heuristic for when to shrink the vm_area?
+	 */
 	if (size <= old_size) {
-		/*
-		 * TODO: Shrink the vm_area, i.e. unmap and free unused pages.
-		 * What would be a good heuristic for when to shrink the
-		 * vm_area?
-		 */
+		/* Zero out spare memory. */
+		if (want_init_on_alloc(flags))
+			memset((void *)p + size, 0, old_size - size);
+
 		return (void *)p;
 	}
 
-- 
2.45.2