Re: [PATCH v2] mm: increase totalram_pages on freeing to buddy system

[Nathan Chancellor <nathan@kernel.org>]

Hi Wei,

On Fri, Jul 26, 2024 at 12:36:12AM +0000, Wei Yang wrote:
> Total memory represents pages managed by buddy system. After the
> introduction of DEFERRED_STRUCT_PAGE_INIT, it may count the pages before
> being managed.
> 
> free_low_memory_core_early() returns number of pages for all free pages,
> even at this moment only early initialized pages are freed to buddy
> system. This means the total memory at this moment is not correct.
> 
> Let's increase it when pages are freed to buddy system.
> 
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> CC: David Hildenbrand <david@redhat.com>
> 
> ---
> v2:
>   * rebase on current master
>   * those places would be affected are merged
> ---
>  mm/memblock.c   | 22 ++++++----------------
>  mm/page_alloc.c |  4 +---
>  2 files changed, 7 insertions(+), 19 deletions(-)
> 
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 213057603b65..592a22b64682 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -1711,10 +1711,8 @@ void __init memblock_free_late(phys_addr_t base, phys_addr_t size)
>  	cursor = PFN_UP(base);
>  	end = PFN_DOWN(base + size);
>  
> -	for (; cursor < end; cursor++) {
> +	for (; cursor < end; cursor++)
>  		memblock_free_pages(pfn_to_page(cursor), cursor, 0);
> -		totalram_pages_inc();
> -	}
>  }
>  
>  /*
> @@ -2140,7 +2138,7 @@ static void __init __free_pages_memory(unsigned long start, unsigned long end)
>  	}
>  }
>  
> -static unsigned long __init __free_memory_core(phys_addr_t start,
> +static void __init __free_memory_core(phys_addr_t start,
>  				 phys_addr_t end)
>  {
>  	unsigned long start_pfn = PFN_UP(start);
> @@ -2148,11 +2146,9 @@ static unsigned long __init __free_memory_core(phys_addr_t start,
>  				      PFN_DOWN(end), max_low_pfn);
>  
>  	if (start_pfn >= end_pfn)
> -		return 0;
> +		return;
>  
>  	__free_pages_memory(start_pfn, end_pfn);
> -
> -	return end_pfn - start_pfn;
>  }
>  
>  static void __init memmap_init_reserved_pages(void)
> @@ -2194,9 +2190,8 @@ static void __init memmap_init_reserved_pages(void)
>  	}
>  }
>  
> -static unsigned long __init free_low_memory_core_early(void)
> +static void __init free_low_memory_core_early(void)
>  {
> -	unsigned long count = 0;
>  	phys_addr_t start, end;
>  	u64 i;
>  
> @@ -2211,9 +2206,7 @@ static unsigned long __init free_low_memory_core_early(void)
>  	 */
>  	for_each_free_mem_range(i, NUMA_NO_NODE, MEMBLOCK_NONE, &start, &end,
>  				NULL)
> -		count += __free_memory_core(start, end);
> -
> -	return count;
> +		__free_memory_core(start, end);
>  }
>  
>  static int reset_managed_pages_done __initdata;
> @@ -2244,13 +2237,10 @@ void __init reset_all_zones_managed_pages(void)
>   */
>  void __init memblock_free_all(void)
>  {
> -	unsigned long pages;
> -
>  	free_unused_memmap();
>  	reset_all_zones_managed_pages();
>  
> -	pages = free_low_memory_core_early();
> -	totalram_pages_add(pages);
> +	free_low_memory_core_early();
>  }
>  
>  /* Keep a table to reserve named memory */
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 71d2716a554f..4701bc442df6 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1248,16 +1248,14 @@ void __meminit __free_pages_core(struct page *page, unsigned int order,
>  		 * map it first.
>  		 */
>  		debug_pagealloc_map_pages(page, nr_pages);
> -		adjust_managed_page_count(page, nr_pages);
>  	} else {
>  		for (loop = 0; loop < nr_pages; loop++, p++) {
>  			__ClearPageReserved(p);
>  			set_page_count(p, 0);
>  		}
>  
> -		/* memblock adjusts totalram_pages() manually. */
> -		atomic_long_add(nr_pages, &page_zone(page)->managed_pages);
>  	}
> +	adjust_managed_page_count(page, nr_pages);
>  
>  	if (page_contains_unaccepted(page, order)) {
>  		if (order == MAX_PAGE_ORDER && __free_unaccepted(page))
> -- 
> 2.34.1
> 
> 

After this change as commit 0e690b558b53 ("mm: increase totalram_pages
on freeing to buddy system") in -next, I see an issue when booting
OpenSUSE's powerpc64le configuration in QEMU (I have not tried to see if
there is a specific configuration option triggers this yet but it does
not happen with all of my powerpc configurations):

$ curl -LSso .config https://github.com/openSUSE/kernel-source/raw/master/config/ppc64le/default

$ make -skj"$(nproc)" ARCH=powerpc CROSS_COMPILE=powerpc64-linux- olddefconfig zImage.epapr

$ qemu-system-ppc64 \
    -display none \
    -nodefaults \
    -device ipmi-bmc-sim,id=bmc0 \
    -device isa-ipmi-bt,bmc=bmc0,irq=10 \
    -machine powernv \
    -kernel arch/powerpc/boot/zImage.epapr \
    -initrd rootfs.cpio \
    -m 2G \
    -serial mon:stdio
...
[    0.000000][    T0] Linux version 6.11.0-rc1-default+ (nathan@thelio-3990X) (powerpc64-linux-gcc (GCC) 14.1.0, GNU ld (GNU Binutils) 2.42) #1 SMP Fri Aug  2 16:58:44 MST 2024
...
[    1.583547][    T1] Run /init as init process
/init: exec: line 15: /sbin/init: not found
[    1.810389][    T1] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00007f00
[    1.811467][    T1] CPU: 0 UID: 0 PID: 1 Comm: init Not tainted 6.11.0-rc1-default+ #1 531e1f40bec7af44d9126123987f957a9e2338c9
[    1.812238][    T1] Hardware name: IBM PowerNV (emulated by qemu) POWER10 0x801200 opal:v7.1 PowerNV
[    1.812801][    T1] Call Trace:
[    1.813011][    T1] [c0000000031f79b0] [c000000001036910] dump_stack_lvl+0x84/0xc0 (unreliable)
[    1.813977][    T1] [c0000000031f79e0] [c00000000015c1c0] panic+0x174/0x454
[    1.814298][    T1] [c0000000031f7a80] [c0000000001658c0] do_exit+0xb70/0xb80
[    1.814648][    T1] [c0000000031f7b50] [c000000000165b3c] do_group_exit+0x4c/0xc0
[    1.814975][    T1] [c0000000031f7b90] [c000000000165bd8] sys_exit_group+0x28/0x30
[    1.815307][    T1] [c0000000031f7bb0] [c00000000002e850] system_call_exception+0x120/0x240
[    1.815704][    T1] [c0000000031f7e50] [c00000000000cfdc] system_call_vectored_common+0x15c/0x2ec
[    1.816108][    T1] --- interrupt: 3000 at 0x7fff88e61bd8
[    1.816561][    T1] NIP:  00007fff88e61bd8 LR: 00007fff88e61bd8 CTR: 0000000000000000
[    1.816910][    T1] REGS: c0000000031f7e80 TRAP: 3000   Not tainted  (6.11.0-rc1-default+)
[    1.817301][    T1] MSR:  900000000280f033 <SF,HV,VEC,VSX,EE,PR,FP,ME,IR,DR,RI,LE>  CR: 42002828  XER: 00000000
[    1.817866][    T1] IRQMASK: 0
[    1.817866][    T1] GPR00: 00000000000000ea 00007ffff22b6400 00007fff88f57300 000000000000007f
[    1.817866][    T1] GPR04: 0000000000000000 00007ffff22b6600 00007ffff22b6610 00007fff8900ad00
[    1.817866][    T1] GPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[    1.817866][    T1] GPR12: 0000000000000000 00007fff8900ad00 0000000000000000 0000000000000000
[    1.817866][    T1] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[    1.817866][    T1] GPR20: 0000000000000000 0000000000000000 00007fff89000000 000000011cf103f8
[    1.817866][    T1] GPR24: 00007ffff22b6f70 0000000000000000 00007ffff22b6f58 00007fff890012a0
[    1.817866][    T1] GPR28: 0000000000000002 fffffffffffff000 000000000000007f 00007fff89003d10
[    1.821081][    T1] NIP [00007fff88e61bd8] 0x7fff88e61bd8
[    1.821327][    T1] LR [00007fff88e61bd8] 0x7fff88e61bd8
[    1.821577][    T1] --- interrupt: 3000
[    1.823172][    T1] Rebooting in 90 seconds.

The rootfs is available from [1] (arm-rootfs.cpio.zst, decompress it
with zstd first); it just shuts down the machine on boot.

If there is any other information I can provide or patches I can test, I
am more than happy to do so.

Cheers,
Nathan

[1]: https://github.com/ClangBuiltLinux/boot-utils/releases/latest

# bad: [f524a5e4dfb75b277c9a5ad819ca5f035f490f14] Add linux-next specific files for 20240802
# good: [c0ecd6388360d930440cc5554026818895199923] Merge tag 'pci-v6.11-fixes-1' of git://git.kernel.org/pub/scm/linux/kernel/git/pci/pci
git bisect start 'f524a5e4dfb75b277c9a5ad819ca5f035f490f14' 'c0ecd6388360d930440cc5554026818895199923'
# bad: [ef6591d6312c51ae1d10c5e89e6e1e76f06a464f] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git
git bisect bad ef6591d6312c51ae1d10c5e89e6e1e76f06a464f
# bad: [5c8256684186fe9d766fa96c9f9de693beda6deb] Merge branch 'for-next' of https://github.com/sophgo/linux.git
git bisect bad 5c8256684186fe9d766fa96c9f9de693beda6deb
# bad: [a97441aa9432ebdceb6216d14553f88555d2f980] Merge branch 'mm-everything' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
git bisect bad a97441aa9432ebdceb6216d14553f88555d2f980
# good: [961f57fbf5386c7e04bb8e8d2467bca5ab96b11d] Merge branch 'clk-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux.git
git bisect good 961f57fbf5386c7e04bb8e8d2467bca5ab96b11d
# bad: [0e690b558b53293f236ebd80b73e90e510c624c9] mm: increase totalram_pages on freeing to buddy system
git bisect bad 0e690b558b53293f236ebd80b73e90e510c624c9
# good: [1e29ee6c9f6b04bf40cffdffb21853fd77ca0163] mm/swap: rename cpu_fbatches->activate
git bisect good 1e29ee6c9f6b04bf40cffdffb21853fd77ca0163
# good: [d88e021d3f5bd6708b786ca129b187d6e6e9de69] s390/uv: drop arch_make_page_accessible()
git bisect good d88e021d3f5bd6708b786ca129b187d6e6e9de69
# good: [dedad7f924e24c1ad124b4586f8b937614ddc1d8] mm/cma: change the addition of totalcma_pages in the cma_init_reserved_mem
git bisect good dedad7f924e24c1ad124b4586f8b937614ddc1d8
# good: [0e004bbadb9c350807ff253335152b516a6f0083] slub: introduce CONFIG_SLUB_RCU_DEBUG
git bisect good 0e004bbadb9c350807ff253335152b516a6f0083
# good: [726459950d9f530a7bc4410b88573bbfd9563560] mm: document __GFP_NOFAIL must be blockable
git bisect good 726459950d9f530a7bc4410b88573bbfd9563560
# good: [6284ca1e5dd29188a970b188b0da5bb9142f3e91] mm: prohibit NULL deference exposed for unsupported non-blockable __GFP_NOFAIL
git bisect good 6284ca1e5dd29188a970b188b0da5bb9142f3e91
# good: [9cd03c3e91270d0e9d0d7e57c81dc10c1de94f6a] mm/memory_hotplug: get rid of __ref
git bisect good 9cd03c3e91270d0e9d0d7e57c81dc10c1de94f6a
# first bad commit: [0e690b558b53293f236ebd80b73e90e510c624c9] mm: increase totalram_pages on freeing to buddy system