Re: [PATCH v4 1/2] mm/memblock: Add reserved memory release function

[Wei Yang]

On Wed, Feb 19, 2025 at 12:08:58AM +0900, Masami Hiramatsu (Google) wrote:
>From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
>
>Add reserve_mem_release_by_name() to release a reserved memory region
>with a given name. This allows us to release reserved memory which is
>defined by kernel cmdline, after boot.
>
>Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
>Acked-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
>Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>Cc: linux-mm@xxxxxxxxx
>---
> Changes in v4:
>  - Use free_reserved_area() according to Mike's comment.
> Changes in v2:
>  - Rename reserved_mem_* to reserve_mem_*.
>---
> include/linux/mm.h |    1 +
> mm/memblock.c      |   66 +++++++++++++++++++++++++++++++++++++++++++---------
> 2 files changed, 55 insertions(+), 12 deletions(-)
>
>diff --git a/include/linux/mm.h b/include/linux/mm.h
>index 7b1068ddcbb7..1ee9e7447485 100644
>--- a/include/linux/mm.h
>+++ b/include/linux/mm.h
>@@ -4123,6 +4123,7 @@ void vma_pgtable_walk_begin(struct vm_area_struct *vma);
> void vma_pgtable_walk_end(struct vm_area_struct *vma);
> 
> int reserve_mem_find_by_name(const char *name, phys_addr_t *start, phys_addr_t *size);
>+int reserve_mem_release_by_name(const char *name);
> 
> #ifdef CONFIG_64BIT
> int do_mseal(unsigned long start, size_t len_in, unsigned long flags);
>diff --git a/mm/memblock.c b/mm/memblock.c
>index 95af35fd1389..8cd95f60015d 100644
>--- a/mm/memblock.c
>+++ b/mm/memblock.c
>@@ -16,6 +16,7 @@
> #include <linux/kmemleak.h>
> #include <linux/seq_file.h>
> #include <linux/memblock.h>
>+#include <linux/mutex.h>
> 
> #include <asm/sections.h>
> #include <linux/io.h>
>@@ -2283,6 +2284,7 @@ struct reserve_mem_table {
> };
> static struct reserve_mem_table reserved_mem_table[RESERVE_MEM_MAX_ENTRIES];
> static int reserved_mem_count;
>+static DEFINE_MUTEX(reserve_mem_lock);
> 

This looks break the memblock tests in tools/testing/memblock.

memblock.c:2289:8: warning: type defaults to ‘int’ in declaration of ‘DEFINE_MUTEX’ [-Wimplicit-int]
 2289 | static DEFINE_MUTEX(reserve_mem_lock);
      |        ^~~~~~~~~~~~
memblock.c:2289:1: warning: parameter names (without types) in function declaration
 2289 | static DEFINE_MUTEX(reserve_mem_lock);
      | ^~~~~~
memblock.c: In function ‘reserve_mem_find_by_name’:
memblock.c:2332:9: warning: implicit declaration of function ‘guard’ [-Wimplicit-function-declaration]
 2332 |         guard(mutex)(&reserve_mem_lock);
      |         ^~~~~