Re: [PATCH v2 1/2] mm/memblock: expose only miminal interface to add/walk physmem

From: Mike Rapoport
Date: Wed Jul 01 2020 - 11:07:00 EST

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In reply to: David Hildenbrand: "[PATCH v2 1/2] mm/memblock: expose only miminal interface to add/walk physmem"
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Hi David,

On Wed, Jul 01, 2020 at 04:18:29PM +0200, David Hildenbrand wrote:
> "physmem" in the memblock allocator is somewhat weird: it's not actually
> used for allocation, it's simply information collected during boot, which
> describes the unmodified physical memory map at boot time, without any
> standby/hotplugged memory. It's only used on s390x and is currently the
> only reason s390x keeps using CONFIG_ARCH_KEEP_MEMBLOCK.
>
> Physmem isn't numa aware and current users don't specify any flags. Let's
> hide it from the user, exposing only for_each_physmem(), and simplify. The
> interface for physmem is now really minimalistic:
> - memblock_physmem_add() to add ranges
> - for_each_physmem() / __next_physmem_range() to walk physmem ranges
>
> Don't place it into an __init section and don't discard it without
> CONFIG_ARCH_KEEP_MEMBLOCK. As we're reusing __next_mem_range(), remove
> the __meminit notifier to avoid section mismatch warnings once
> CONFIG_ARCH_KEEP_MEMBLOCK is no longer used with
> CONFIG_HAVE_MEMBLOCK_PHYS_MAP.
>
> While fixing up the documentation, sneak in some related cleanups. We can
> stop setting CONFIG_HAVE_MEMBLOCK_PHYS_MAP for s390x next.

As you noted in the previous version it should have been
CONFIG_ARCH_KEEP_MEMBLOCK ;-)

> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
> Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
> Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>

Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>

> ---
> arch/s390/kernel/crash_dump.c | 6 ++--
> include/linux/memblock.h | 28 ++++++++++++++---
> mm/memblock.c | 57 ++++++++++++++++++-----------------
> 3 files changed, 55 insertions(+), 36 deletions(-)
>
> diff --git a/arch/s390/kernel/crash_dump.c b/arch/s390/kernel/crash_dump.c
> index f96a5857bbfde..c42ce348103cc 100644
> --- a/arch/s390/kernel/crash_dump.c
> +++ b/arch/s390/kernel/crash_dump.c
> @@ -549,8 +549,7 @@ static int get_mem_chunk_cnt(void)
> int cnt = 0;
> u64 idx;
>
> - for_each_mem_range(idx, &memblock.physmem, &oldmem_type, NUMA_NO_NODE,
> - MEMBLOCK_NONE, NULL, NULL, NULL)
> + for_each_physmem_range(idx, &oldmem_type, NULL, NULL)
> cnt++;
> return cnt;
> }
> @@ -563,8 +562,7 @@ static void loads_init(Elf64_Phdr *phdr, u64 loads_offset)
> phys_addr_t start, end;
> u64 idx;
>
> - for_each_mem_range(idx, &memblock.physmem, &oldmem_type, NUMA_NO_NODE,
> - MEMBLOCK_NONE, &start, &end, NULL) {
> + for_each_physmem_range(idx, &oldmem_type, &start, &end) {
> phdr->p_filesz = end - start;
> phdr->p_type = PT_LOAD;
> phdr->p_offset = start;
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index 017fae833d4ae..9d925db0d3550 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -77,16 +77,12 @@ struct memblock_type {
> * @current_limit: physical address of the current allocation limit
> * @memory: usable memory regions
> * @reserved: reserved memory regions
> - * @physmem: all physical memory
> */
> struct memblock {
> bool bottom_up; /* is bottom up direction? */
> phys_addr_t current_limit;
> struct memblock_type memory;
> struct memblock_type reserved;
> -#ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP
> - struct memblock_type physmem;
> -#endif
> };
>
> extern struct memblock memblock;
> @@ -145,6 +141,30 @@ void __next_reserved_mem_region(u64 *idx, phys_addr_t *out_start,
>
> void __memblock_free_late(phys_addr_t base, phys_addr_t size);
>
> +#ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP
> +static inline void __next_physmem_range(u64 *idx, struct memblock_type *type,
> + phys_addr_t *out_start,
> + phys_addr_t *out_end)
> +{
> + extern struct memblock_type physmem;
> +
> + __next_mem_range(idx, NUMA_NO_NODE, MEMBLOCK_NONE, &physmem, type,
> + out_start, out_end, NULL);
> +}
> +
> +/**
> + * for_each_physmem_range - iterate through physmem areas not included in type.
> + * @i: u64 used as loop variable
> + * @type: ptr to memblock_type which excludes from the iteration, can be %NULL
> + * @p_start: ptr to phys_addr_t for start address of the range, can be %NULL
> + * @p_end: ptr to phys_addr_t for end address of the range, can be %NULL
> + */
> +#define for_each_physmem_range(i, type, p_start, p_end) \
> + for (i = 0, __next_physmem_range(&i, type, p_start, p_end); \
> + i != (u64)ULLONG_MAX; \
> + __next_physmem_range(&i, type, p_start, p_end))
> +#endif /* CONFIG_HAVE_MEMBLOCK_PHYS_MAP */
> +
> /**
> * for_each_mem_range - iterate through memblock areas from type_a and not
> * included in type_b. Or just type_a if type_b is NULL.
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 39aceafc57f66..45f198750be92 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -44,19 +44,20 @@
> * in the system, for instance when the memory is restricted with
> * ``mem=`` command line parameter
> * * ``reserved`` - describes the regions that were allocated
> - * * ``physmap`` - describes the actual physical memory regardless of
> - * the possible restrictions; the ``physmap`` type is only available
> - * on some architectures.
> + * * ``physmem`` - describes the actual physical memory available during
> + * boot regardless of the possible restrictions and memory hot(un)plug;
> + * the ``physmem`` type is only available on some architectures.
> *
> * Each region is represented by :c:type:`struct memblock_region` that
> * defines the region extents, its attributes and NUMA node id on NUMA
> * systems. Every memory type is described by the :c:type:`struct
> * memblock_type` which contains an array of memory regions along with
> - * the allocator metadata. The memory types are nicely wrapped with
> - * :c:type:`struct memblock`. This structure is statically initialzed
> - * at build time. The region arrays for the "memory" and "reserved"
> - * types are initially sized to %INIT_MEMBLOCK_REGIONS and for the
> - * "physmap" type to %INIT_PHYSMEM_REGIONS.
> + * the allocator metadata. The "memory" and "reserved" types are nicely
> + * wrapped with :c:type:`struct memblock`. This structure is statically
> + * initialized at build time. The region arrays are initially sized to
> + * %INIT_MEMBLOCK_REGIONS for "memory" and %INIT_MEMBLOCK_RESERVED_REGIONS
> + * for "reserved". The region array for "physmem" is initially sized to
> + * %INIT_PHYSMEM_REGIONS.
> * The memblock_allow_resize() enables automatic resizing of the region
> * arrays during addition of new regions. This feature should be used
> * with care so that memory allocated for the region array will not
> @@ -87,8 +88,8 @@
> * function frees all the memory to the buddy page allocator.
> *
> * Unless an architecture enables %CONFIG_ARCH_KEEP_MEMBLOCK, the
> - * memblock data structures will be discarded after the system
> - * initialization completes.
> + * memblock data structures (except "physmem") will be discarded after the
> + * system initialization completes.
> */
>
> #ifndef CONFIG_NEED_MULTIPLE_NODES
> @@ -104,7 +105,7 @@ unsigned long long max_possible_pfn;
> static struct memblock_region memblock_memory_init_regions[INIT_MEMBLOCK_REGIONS] __initdata_memblock;
> static struct memblock_region memblock_reserved_init_regions[INIT_MEMBLOCK_RESERVED_REGIONS] __initdata_memblock;
> #ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP
> -static struct memblock_region memblock_physmem_init_regions[INIT_PHYSMEM_REGIONS] __initdata_memblock;
> +static struct memblock_region memblock_physmem_init_regions[INIT_PHYSMEM_REGIONS];
> #endif
>
> struct memblock memblock __initdata_memblock = {
> @@ -118,17 +119,19 @@ struct memblock memblock __initdata_memblock = {
> .reserved.max = INIT_MEMBLOCK_RESERVED_REGIONS,
> .reserved.name = "reserved",
>
> -#ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP
> - .physmem.regions = memblock_physmem_init_regions,
> - .physmem.cnt = 1, /* empty dummy entry */
> - .physmem.max = INIT_PHYSMEM_REGIONS,
> - .physmem.name = "physmem",
> -#endif
> -
> .bottom_up = false,
> .current_limit = MEMBLOCK_ALLOC_ANYWHERE,
> };
>
> +#ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP
> +struct memblock_type physmem = {
> + .regions = memblock_physmem_init_regions,
> + .cnt = 1, /* empty dummy entry */
> + .max = INIT_PHYSMEM_REGIONS,
> + .name = "physmem",
> +};
> +#endif
> +
> int memblock_debug __initdata_memblock;
> static bool system_has_some_mirror __initdata_memblock = false;
> static int memblock_can_resize __initdata_memblock;
> @@ -838,7 +841,7 @@ int __init_memblock memblock_physmem_add(phys_addr_t base, phys_addr_t size)
> memblock_dbg("%s: [%pa-%pa] %pS\n", __func__,
> &base, &end, (void *)_RET_IP_);
>
> - return memblock_add_range(&memblock.physmem, base, size, MAX_NUMNODES, 0);
> + return memblock_add_range(&physmem, base, size, MAX_NUMNODES, 0);
> }
> #endif
>
> @@ -1019,12 +1022,10 @@ static bool should_skip_region(struct memblock_region *m, int nid, int flags)
> * As both region arrays are sorted, the function advances the two indices
> * in lockstep and returns each intersection.
> */
> -void __init_memblock __next_mem_range(u64 *idx, int nid,
> - enum memblock_flags flags,
> - struct memblock_type *type_a,
> - struct memblock_type *type_b,
> - phys_addr_t *out_start,
> - phys_addr_t *out_end, int *out_nid)
> +void __next_mem_range(u64 *idx, int nid, enum memblock_flags flags,
> + struct memblock_type *type_a,
> + struct memblock_type *type_b, phys_addr_t *out_start,
> + phys_addr_t *out_end, int *out_nid)
> {
> int idx_a = *idx & 0xffffffff;
> int idx_b = *idx >> 32;
> @@ -1924,7 +1925,7 @@ void __init_memblock __memblock_dump_all(void)
> memblock_dump(&memblock.memory);
> memblock_dump(&memblock.reserved);
> #ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP
> - memblock_dump(&memblock.physmem);
> + memblock_dump(&physmem);
> #endif
> }
>
> @@ -2064,8 +2065,8 @@ static int __init memblock_init_debugfs(void)
> debugfs_create_file("reserved", 0444, root,
> &memblock.reserved, &memblock_debug_fops);
> #ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP
> - debugfs_create_file("physmem", 0444, root,
> - &memblock.physmem, &memblock_debug_fops);
> + debugfs_create_file("physmem", 0444, root, &physmem,
> + &memblock_debug_fops);
> #endif
>
> return 0;
> --
> 2.26.2
>

--
Sincerely yours,
Mike.

Next message: Randy Dunlap: "Re: [v2] Documentation: Coccinelle: fix typos and command example"
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In reply to: David Hildenbrand: "[PATCH v2 1/2] mm/memblock: expose only miminal interface to add/walk physmem"
Next in thread: Heiko Carstens: "Re: [PATCH v2 1/2] mm/memblock: expose only miminal interface to add/walk physmem"
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