+ memblock-unpreserve-memory-in-case-of-error.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: memblock: Unpreserve memory in case of error
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     memblock-unpreserve-memory-in-case-of-error.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/memblock-unpreserve-memory-in-case-of-error.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Pasha Tatashin <pasha.tatashin@soleen.com>
Subject: memblock: Unpreserve memory in case of error
Date: Fri, 24 Oct 2025 12:10:02 -0400

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

Link: https://lkml.kernel.org/r/20251024161002.747372-9-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Suggested-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memblock.c |   26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

--- a/mm/memblock.c~memblock-unpreserve-memory-in-case-of-error
+++ a/mm/memblock.c
@@ -2447,6 +2447,7 @@ int reserve_mem_release_by_name(const ch
 
 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);
 	}
_

Patches currently in -mm which might be from pasha.tatashin@soleen.com are

liveupdate-kho-warn-and-fail-on-metadata-or-preserved-memory-in-scratch-area.patch
liveupdate-kho-increase-metadata-bitmap-size-to-page_size.patch
liveupdate-kho-allocate-metadata-directly-from-the-buddy-allocator.patch
kho-allow-to-drive-kho-from-within-kernel.patch
kho-make-debugfs-interface-optional.patch
kho-add-interfaces-to-unpreserve-folios-and-page-ranges.patch
kho-dont-unpreserve-memory-during-abort.patch
liveupdate-kho-move-to-kernel-liveupdate.patch
liveupdate-kho-move-kho-debugfs-directory-to-liveupdate.patch
memblock-unpreserve-memory-in-case-of-error.patch