linux-kernel - [PATCH v1] mm/mm_init: Fix hash table order logging in alloc_large_system

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Message-ID: <20251028191020.413002-1-isaacmanjarres@google.com>
Date: Tue, 28 Oct 2025 12:10:12 -0700
From: "Isaac J. Manjarres" <isaacmanjarres@...gle.com>
To: Mike Rapoport <rppt@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>
Cc: "Isaac J. Manjarres" <isaacmanjarres@...gle.com>, stable@...r.kernel.org, 
	kernel-team@...roid.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1] mm/mm_init: Fix hash table order logging in alloc_large_system_hash()

When emitting the order of the allocation for a hash table,
alloc_large_system_hash() unconditionally subtracts PAGE_SHIFT from
log base 2 of the allocation size. This is not correct if the
allocation size is smaller than a page, and yields a negative value
for the order as seen below:

TCP established hash table entries: 32 (order: -4, 256 bytes, linear)
TCP bind hash table entries: 32 (order: -2, 1024 bytes, linear)

Use get_order() to compute the order when emitting the hash table
information to correctly handle cases where the allocation size is
smaller than a page:

TCP established hash table entries: 32 (order: 0, 256 bytes, linear)
TCP bind hash table entries: 32 (order: 0, 1024 bytes, linear)

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@...r.kernel.org # v5.4+
Signed-off-by: Isaac J. Manjarres <isaacmanjarres@...gle.com>
---
 mm/mm_init.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/mm_init.c b/mm/mm_init.c
index 3db2dea7db4c..7712d887b696 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -2469,7 +2469,7 @@ void *__init alloc_large_system_hash(const char *tablename,
 		panic("Failed to allocate %s hash table\n", tablename);
 
 	pr_info("%s hash table entries: %ld (order: %d, %lu bytes, %s)\n",
-		tablename, 1UL << log2qty, ilog2(size) - PAGE_SHIFT, size,
+		tablename, 1UL << log2qty, get_order(size), size,
 		virt ? (huge ? "vmalloc hugepage" : "vmalloc") : "linear");
 
 	if (_hash_shift)
-- 
2.51.1.851.g4ebd6896fd-goog