linux-kernel - [PATCH v4 1/4] kho: check if kho is finalized in __kho_preserve

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Message-ID: <20250917174033.3810435-2-rppt@kernel.org>
Date: Wed, 17 Sep 2025 20:40:30 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Alexander Graf <graf@...zon.com>,
	Baoquan He <bhe@...hat.com>,
	Changyuan Lyu <changyuanl@...gle.com>,
	Chris Li <chrisl@...nel.org>,
	Jason Gunthorpe <jgg@...dia.com>,
	Mike Rapoport <rppt@...nel.org>,
	Pasha Tatashin <pasha.tatashin@...een.com>,
	Pratyush Yadav <pratyush@...nel.org>,
	kexec@...ts.infradead.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v4 1/4] kho: check if kho is finalized in __kho_preserve_order()

From: "Mike Rapoport (Microsoft)" <rppt@...nel.org>

Instead of checking if kho is finalized in each caller of
__kho_preserve_order(), do it in the core function itself.

Signed-off-by: Mike Rapoport (Microsoft) <rppt@...nel.org>
---
 kernel/kexec_handover.c | 55 +++++++++++++++++++----------------------
 1 file changed, 26 insertions(+), 29 deletions(-)

diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c
index 8079fc4b9189..f421acc58c1f 100644
--- a/kernel/kexec_handover.c
+++ b/kernel/kexec_handover.c
@@ -91,6 +91,29 @@ struct kho_serialization {
 	struct khoser_mem_chunk *preserved_mem_map;
 };
 
+struct kho_out {
+	struct blocking_notifier_head chain_head;
+
+	struct dentry *dir;
+
+	struct mutex lock; /* protects KHO FDT finalization */
+
+	struct kho_serialization ser;
+	bool finalized;
+};
+
+static struct kho_out kho_out = {
+	.chain_head = BLOCKING_NOTIFIER_INIT(kho_out.chain_head),
+	.lock = __MUTEX_INITIALIZER(kho_out.lock),
+	.ser = {
+		.fdt_list = LIST_HEAD_INIT(kho_out.ser.fdt_list),
+		.track = {
+			.orders = XARRAY_INIT(kho_out.ser.track.orders, 0),
+		},
+	},
+	.finalized = false,
+};
+
 static void *xa_load_or_alloc(struct xarray *xa, unsigned long index, size_t sz)
 {
 	void *elm, *res;
@@ -149,6 +172,9 @@ static int __kho_preserve_order(struct kho_mem_track *track, unsigned long pfn,
 
 	might_sleep();
 
+	if (kho_out.finalized)
+		return -EBUSY;
+
 	physxa = xa_load(&track->orders, order);
 	if (!physxa) {
 		int err;
@@ -640,29 +666,6 @@ int kho_add_subtree(struct kho_serialization *ser, const char *name, void *fdt)
 }
 EXPORT_SYMBOL_GPL(kho_add_subtree);
 
-struct kho_out {
-	struct blocking_notifier_head chain_head;
-
-	struct dentry *dir;
-
-	struct mutex lock; /* protects KHO FDT finalization */
-
-	struct kho_serialization ser;
-	bool finalized;
-};
-
-static struct kho_out kho_out = {
-	.chain_head = BLOCKING_NOTIFIER_INIT(kho_out.chain_head),
-	.lock = __MUTEX_INITIALIZER(kho_out.lock),
-	.ser = {
-		.fdt_list = LIST_HEAD_INIT(kho_out.ser.fdt_list),
-		.track = {
-			.orders = XARRAY_INIT(kho_out.ser.track.orders, 0),
-		},
-	},
-	.finalized = false,
-};
-
 int register_kho_notifier(struct notifier_block *nb)
 {
 	return blocking_notifier_chain_register(&kho_out.chain_head, nb);
@@ -690,9 +693,6 @@ int kho_preserve_folio(struct folio *folio)
 	const unsigned int order = folio_order(folio);
 	struct kho_mem_track *track = &kho_out.ser.track;
 
-	if (kho_out.finalized)
-		return -EBUSY;
-
 	return __kho_preserve_order(track, pfn, order);
 }
 EXPORT_SYMBOL_GPL(kho_preserve_folio);
@@ -716,9 +716,6 @@ int kho_preserve_phys(phys_addr_t phys, size_t size)
 	int err = 0;
 	struct kho_mem_track *track = &kho_out.ser.track;
 
-	if (kho_out.finalized)
-		return -EBUSY;
-
 	if (!PAGE_ALIGNED(phys) || !PAGE_ALIGNED(size))
 		return -EINVAL;
 
-- 
2.50.1