Re: [PATCH v4 3/5] memblock: add memblock_cap_memory_ranges for multiple ranges

[Mike Rapoport]

Hi,

On Mon, Apr 15, 2019 at 06:57:23PM +0800, Chen Zhou wrote:
> The memblock_cap_memory_range() removes all the memory except the
> range passed to it. Extend this function to receive memblock_type
> with the regions that should be kept.
> 
> Enable this function in arm64 for reservation of multiple regions
> for the crash kernel.
> 
> Signed-off-by: Chen Zhou <chenzhou10@xxxxxxxxxx>
> Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>

I didn't work on this version, please drop the signed-off.

> ---
>  include/linux/memblock.h |  1 +
>  mm/memblock.c            | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 46 insertions(+)
> 
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index 47e3c06..180877c 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -446,6 +446,7 @@ phys_addr_t memblock_start_of_DRAM(void);
>  phys_addr_t memblock_end_of_DRAM(void);
>  void memblock_enforce_memory_limit(phys_addr_t memory_limit);
>  void memblock_cap_memory_range(phys_addr_t base, phys_addr_t size);
> +void memblock_cap_memory_ranges(struct memblock_type *regions_to_keep);
>  void memblock_mem_limit_remove_map(phys_addr_t limit);
>  bool memblock_is_memory(phys_addr_t addr);
>  bool memblock_is_map_memory(phys_addr_t addr);
> diff --git a/mm/memblock.c b/mm/memblock.c
> index f315eca..9661807 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -1697,6 +1697,51 @@ void __init memblock_cap_memory_range(phys_addr_t base, phys_addr_t size)
>  			base + size, PHYS_ADDR_MAX);
>  }
>  
> +void __init memblock_cap_memory_ranges(struct memblock_type *regions_to_keep)
> +{
> +	int start_rgn[INIT_MEMBLOCK_REGIONS], end_rgn[INIT_MEMBLOCK_REGIONS];
> +	int i, j, ret, nr = 0;
> +	struct memblock_region *regs = regions_to_keep->regions;
> +
> +	for (i = 0; i < regions_to_keep->cnt; i++) {
> +		ret = memblock_isolate_range(&memblock.memory, regs[i].base,
> +				regs[i].size, &start_rgn[i], &end_rgn[i]);
> +		if (ret)
> +			break;
> +		nr++;
> +	}
> +	if (!nr)
> +		return;
> +
> +	/* remove all the MAP regions */
> +	for (i = memblock.memory.cnt - 1; i >= end_rgn[nr - 1]; i--)
> +		if (!memblock_is_nomap(&memblock.memory.regions[i]))
> +			memblock_remove_region(&memblock.memory, i);
> +
> +	for (i = nr - 1; i > 0; i--)
> +		for (j = start_rgn[i] - 1; j >= end_rgn[i - 1]; j--)
> +			if (!memblock_is_nomap(&memblock.memory.regions[j]))
> +				memblock_remove_region(&memblock.memory, j);
> +
> +	for (i = start_rgn[0] - 1; i >= 0; i--)
> +		if (!memblock_is_nomap(&memblock.memory.regions[i]))
> +			memblock_remove_region(&memblock.memory, i);
> +
> +	/* truncate the reserved regions */
> +	memblock_remove_range(&memblock.reserved, 0, regs[0].base);
> +
> +	for (i = nr - 1; i > 0; i--) {
> +		phys_addr_t remove_base = regs[i - 1].base + regs[i - 1].size;
> +		phys_addr_t remove_size = regs[i].base - remove_base;
> +
> +		memblock_remove_range(&memblock.reserved, remove_base,
> +				remove_size);
> +	}
> +
> +	memblock_remove_range(&memblock.reserved,
> +			regs[nr - 1].base + regs[nr - 1].size, PHYS_ADDR_MAX);
> +}
> +

I've double-checked and I see no problem with using
for_each_mem_range_rev() iterators for removing some ranges. And with them
this functions becomes much clearer and more efficient.

Can you please check if the below patch works for you?