linux-kernel - [PATCH] memblock: fix kernel-doc for MEMBLOCK_RSRV

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Message-ID: <20250826071947.1949725-1-rppt@kernel.org>
Date: Tue, 26 Aug 2025 10:19:46 +0300
From: Mike Rapoport <rppt@...nel.org>
To: linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...hat.com>,
	Mike Rapoport <rppt@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] memblock: fix kernel-doc for MEMBLOCK_RSRV_NOINIT

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

The kernel-doc description of MEMBLOCK_RSRV_NOINIT and
memblock_reserved_mark_noinit() do not accurately describe their
functionality.

Expand their kernel doc to make it clear that the user of
MEMBLOCK_RSRV_NOINIT is responsible to properly initialize the struct pages
for such regions and add more details about effects of using this flag.

Signed-off-by: Mike Rapoport (Microsoft) <rppt@...nel.org>
---
 include/linux/memblock.h |  5 +++--
 mm/memblock.c            | 15 +++++++++++----
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index b96746376e17..fcda8481de9a 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -40,8 +40,9 @@ extern unsigned long long max_possible_pfn;
  * via a driver, and never indicated in the firmware-provided memory map as
  * system RAM. This corresponds to IORESOURCE_SYSRAM_DRIVER_MANAGED in the
  * kernel resource tree.
- * @MEMBLOCK_RSRV_NOINIT: memory region for which struct pages are
- * not initialized (only for reserved regions).
+ * @MEMBLOCK_RSRV_NOINIT: reserved memory region for which struct pages are not
+ * fully initialized. Users of this flag are responsible to properly initialize
+ * struct pages of this region
  * @MEMBLOCK_RSRV_KERN: memory region that is reserved for kernel use,
  * either explictitly with memblock_reserve_kern() or via memblock
  * allocation APIs. All memblock allocations set this flag.
diff --git a/mm/memblock.c b/mm/memblock.c
index 154f1d73b61f..46b411fb3630 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1091,13 +1091,20 @@ int __init_memblock memblock_clear_nomap(phys_addr_t base, phys_addr_t size)
 
 /**
  * memblock_reserved_mark_noinit - Mark a reserved memory region with flag
- * MEMBLOCK_RSRV_NOINIT which results in the struct pages not being initialized
- * for this region.
+ * MEMBLOCK_RSRV_NOINIT
+ *
  * @base: the base phys addr of the region
  * @size: the size of the region
  *
- * struct pages will not be initialized for reserved memory regions marked with
- * %MEMBLOCK_RSRV_NOINIT.
+ * The struct pages for the reserved regions marked %MEMBLOCK_RSRV_NOINIT will
+ * not be fully initialized to allow the caller optimize their initialization.
+ *
+ * When %CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled, setting this flag
+ * completely bypasses the initialization of struct pages for such region.
+ *
+ * When %CONFIG_DEFERRED_STRUCT_PAGE_INIT is disabled, struct pages in this
+ * region will be initialized with default values but won't be marked as
+ * reserved.
  *
  * Return: 0 on success, -errno on failure.
  */
-- 
2.50.1