linux-kernel - [PATCH v8 8/8] memblock: Unpreserve memory in case of error

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Message-ID: <20251024161002.747372-9-pasha.tatashin@soleen.com>
Date: Fri, 24 Oct 2025 12:10:02 -0400
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: akpm@...ux-foundation.org,
	brauner@...nel.org,
	corbet@....net,
	graf@...zon.com,
	jgg@...pe.ca,
	linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	linux-mm@...ck.org,
	masahiroy@...nel.org,
	ojeda@...nel.org,
	pasha.tatashin@...een.com,
	pratyush@...nel.org,
	rdunlap@...radead.org,
	rppt@...nel.org,
	tj@...nel.org
Subject: [PATCH v8 8/8] memblock: Unpreserve memory in case of error

If there is an error half way through KHO memory preservation, we should
rollback and unpreserve everything that is partially preserved.

Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
Suggested-by: Pratyush Yadav <pratyush@...nel.org>
---
 mm/memblock.c | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/mm/memblock.c b/mm/memblock.c
index e3bef9b35d63..5ceaa02af7d6 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -2447,6 +2447,7 @@ int reserve_mem_release_by_name(const char *name)
 
 static int __init prepare_kho_fdt(void)
 {
+	bool fdt_folio_preserved = false;
 	int err = 0, i;
 	struct page *fdt_page;
 	void *fdt;
@@ -2462,12 +2463,14 @@ static int __init prepare_kho_fdt(void)
 
 	err |= fdt_begin_node(fdt, "");
 	err |= fdt_property_string(fdt, "compatible", MEMBLOCK_KHO_NODE_COMPATIBLE);
-	for (i = 0; i < reserved_mem_count; i++) {
+	for (i = 0; !err && i < reserved_mem_count; i++) {
 		struct reserve_mem_table *map = &reserved_mem_table[i];
 		struct page *page = phys_to_page(map->start);
 		unsigned int nr_pages = map->size >> PAGE_SHIFT;
 
-		err |= kho_preserve_pages(page, nr_pages);
+		err = kho_preserve_pages(page, nr_pages);
+		if (err)
+			break;
 		err |= fdt_begin_node(fdt, map->name);
 		err |= fdt_property_string(fdt, "compatible", RESERVE_MEM_KHO_NODE_COMPATIBLE);
 		err |= fdt_property(fdt, "start", &map->start, sizeof(map->start));
@@ -2477,12 +2480,27 @@ static int __init prepare_kho_fdt(void)
 	err |= fdt_end_node(fdt);
 	err |= fdt_finish(fdt);
 
-	err |= kho_preserve_folio(page_folio(fdt_page));
-
 	if (!err)
+		err = kho_preserve_folio(page_folio(fdt_page));
+
+	if (!err) {
+		fdt_folio_preserved = true;
 		err = kho_add_subtree(MEMBLOCK_KHO_FDT, fdt);
+	}
 
 	if (err) {
+		int nr_reserve_map_preserved = i;
+
+		for (i = 0; i < nr_reserve_map_preserved; i++) {
+			struct reserve_mem_table *map = &reserved_mem_table[i];
+			struct page *page = phys_to_page(map->start);
+			unsigned int nr_pages = map->size >> PAGE_SHIFT;
+
+			kho_unpreserve_pages(page, nr_pages);
+		}
+		if (fdt_folio_preserved)
+			kho_unpreserve_folio(page_folio(fdt_page));
+
 		pr_err("failed to prepare memblock FDT for KHO: %d\n", err);
 		put_page(fdt_page);
 	}
-- 
2.51.1.821.gb6fe4d2222-goog