linux-kernel - Re: [PATCH v4 5/6] x86/numa: Provide a range-to-target

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Message-ID: <874kvu3egp.fsf@nanos.tec.linutronix.de>
Date:   Thu, 13 Feb 2020 12:37:42 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Dan Williams <dan.j.williams@...el.com>, mingo@...hat.com
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Michal Hocko <mhocko@...e.com>,
        kbuild test robot <lkp@...el.com>, vishal.l.verma@...el.com,
        hch@....de, linux-kernel@...r.kernel.org,
        linux-nvdimm@...ts.01.org, x86@...nel.org
Subject: Re: [PATCH v4 5/6] x86/numa: Provide a range-to-target_node lookup facility

Dan Williams <dan.j.williams@...el.com> writes:
> +/**
> + * numa_move_memblk - Move one numa_memblk from one numa_meminfo to another
> + * @dst: numa_meminfo to move block to
> + * @idx: Index of memblk to remove
> + * @src: numa_meminfo to remove memblk from
> + *
> + * If @dst is non-NULL add it at the @dst->nr_blks index and increment
> + * @dst->nr_blks, then remove it from @src.

This is not correct. It's suggesting that these operations are only
happening when @dst is non-NULL. Remove is unconditional though.

Also this is called with &numa_reserved_meminfo as @dst argument, which is:

> +static struct numa_meminfo numa_reserved_meminfo __initdata_numa;

So how would @dst ever be NULL?
 
> + */
> +static void __init numa_move_memblk(struct numa_meminfo *dst, int idx,
> +		struct numa_meminfo *src)
> +{
> +	if (dst) {
> +		memcpy(&dst->blk[dst->nr_blks], &src->blk[idx],
> +				sizeof(struct numa_memblk));
> +		dst->nr_blks++;
> +	}
> +	numa_remove_memblk_from(idx, src);
> +}

...

> -		/* make sure all blocks are inside the limits */
> +		/* move / save reserved memory ranges */
> +		if (!memblock_overlaps_region(&memblock.memory,
> +					bi->start, bi->end - bi->start)) {
> +			numa_move_memblk(&numa_reserved_meminfo, i--, mi);

Thanks,

        tglx