linux-kernel - [PATCH] memblock: report failures when memblock_can

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Date:   Sat, 24 Jun 2023 11:26:07 +0800
From:   Song Shuai <songshuaishuai@...ylab.org>
To:     rppt@...nel.org, akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Song Shuai <songshuaishuai@...ylab.org>
Subject: [PATCH] memblock: report failures when memblock_can_resize is not set

The callers of memblock_reserve() do not check the return value
presuming that memblock_reserve() always succeeds, but there are
cases where it may fail.

Having numerous memblock reservations at early boot where
memblock_can_resize is unset may exhaust the INIT_MEMBLOCK_REGIONS sized
memblock.reserved regions array and an attempt to double this array via
memblock_double_array() will fail and will return -1 to the caller.

When this happens the system crashes anyway, but it's hard to identify
the reason for the crash.

Add a panic message to memblock_double_array() to aid debugging of the
cases when too many regions are reserved before memblock can resize
memblock.reserved array.

Link: https://lore.kernel.org/linux-kernel/20230614131746.3670303-1-songshuaishuai@tinylab.org/
Signed-off-by: Song Shuai <songshuaishuai@...ylab.org>
---
 mm/memblock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memblock.c b/mm/memblock.c
index 3feafea06ab2..1b8e902490e5 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -419,7 +419,7 @@ static int __init_memblock memblock_double_array(struct memblock_type *type,
 	 * of memory that aren't suitable for allocation
 	 */
 	if (!memblock_can_resize)
-		return -1;
+		panic("memblock: cannot resize %s array\n", type->name);

 	/* Calculate new doubled size */
 	old_size = type->max * sizeof(struct memblock_region);
-- 
2.20.1