Re: [PATCH v2 RESEND 2/3] mm: memblock: show all region flags in debugfs

[Mike Rapoport <rppt@kernel.org>]

On Fri, Aug 21, 2026 at 10:09:09AM +0800, Meijing Zhao wrote:
> From: Meijing Zhao <zhaomeijing@lixiang.com>
> 
> Commit 493f349e38d0 ("memblock: Add flags and nid info in memblock
> debugfs") made memblock_debug_show() stop after finding the first set
> flag. A memblock region can carry multiple flags, so the remaining flags
> are hidden from debugfs.
> 
> In particular, memory allocated for HugeTLB pages is reserved with both
> MEMBLOCK_RSRV_KERN and MEMBLOCK_RSRV_HUGETLB, but debugfs only reports
> RSV_KERN.
> 
> Walk all bits in the region flags and print every set flag separated by
> "|". Keep walking beyond flagname[] so that a set flag without a known
> name is reported as UNKNOWN rather than silently ignored.
> 
> A HugeTLB reservation is now shown as:
> 
>   RSV_KERN|RSV_HUGETLB
> 
> instead of:
> 
>   RSV_KERN
> 
> Fixes: 493f349e38d0 ("memblock: Add flags and nid info in memblock debugfs")
> Signed-off-by: Meijing Zhao <zhaomeijing@lixiang.com>
> ---
>  mm/memblock.c | 22 ++++++++++++++--------
>  1 file changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/memblock.c b/mm/memblock.c
> index f2952d725c10..36a8d2a9378d 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -2895,7 +2895,9 @@ static int memblock_debug_show(struct seq_file *m, void *private)
>  	struct memblock_region *reg;
>  	int i, j, nid;
>  	unsigned int count = ARRAY_SIZE(flagname);
> +	unsigned int flags;
>  	phys_addr_t end;
> +	bool first;
>  
>  	for (i = 0; i < type->cnt; i++) {
>  		reg = &type->regions[i];
> @@ -2909,16 +2911,20 @@ static int memblock_debug_show(struct seq_file *m, void *private)
>  		else
>  			seq_printf(m, "%4c ", 'x');
>  		if (reg->flags) {
> -			for (j = 0; j < count; j++) {
> -				if (reg->flags & (1U << j)) {
> -					seq_printf(m, "%s\n", flagname[j]);
> -					break;
> -				}
> +			flags = reg->flags;
> +			first = true;

first and flags can be declared here.

> +			for (j = 0; flags; j++, flags >>= 1) {
> +				if (!(flags & 1))
> +					continue;
> +				if (!first)
> +					seq_putc(m, '|');
> +				seq_puts(m, j < count && flagname[j] ?
> +					 flagname[j] : "UNKNOWN");

Can we really have both j < count and !flagname[j]?

> +				first = false;
>  			}
> -			if (j == count)
> -				seq_printf(m, "%s\n", "UNKNOWN");
> +			seq_putc(m, '\n');
>  		} else {
> -			seq_printf(m, "%s\n", "NONE");
> +			seq_puts(m, "NONE\n");

No need to change this

>  		}
>  	}
>  	return 0;
> -- 
> 2.25.1
> 

-- 
Sincerely yours,
Mike.