Re: [PATCH v29 1/9] memblock: add memblock_cap_memory_range()

[Dennis Chen <dennis.chen@arm.com>]

On Tue, Jan 10, 2017 at 11:16:18AM +0000, Will Deacon wrote:
> [adding some more folks to cc]
> 
> On Wed, Dec 28, 2016 at 01:35:25PM +0900, AKASHI Takahiro wrote:
> > Add memblock_cap_memory_range() which will remove all the memblock regions
> > except the memory range specified in the arguments. In addition, rework is
> > done on memblock_mem_limit_remove_map() to re-implement it using
> > memblock_cap_memory_range().
> > 
> > This function, like memblock_mem_limit_remove_map(), will not remove
> > memblocks with MEMMAP_NOMAP attribute as they may be mapped and accessed
> > later as "device memory."
> > See the commit a571d4eb55d8 ("mm/memblock.c: add new infrastructure to
> > address the mem limit issue").
> > 
> > This function is used, in a succeeding patch in the series of arm64 kdump
> > suuport, to limit the range of usable memory, or System RAM, on crash dump
> > kernel.
> > (Please note that "mem=" parameter is of little use for this purpose.)
> > 
> > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> > Reviewed-by: Will Deacon <will.deacon@arm.com>
> > Acked-by: Catalin Marinas <catalin.marinas@arm.com>
> > Cc: linux-mm@kvack.org
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > ---
> >  include/linux/memblock.h |  1 +
> >  mm/memblock.c            | 44 +++++++++++++++++++++++++++++---------------
> >  2 files changed, 30 insertions(+), 15 deletions(-)
> 
> Whilst this patch looks fine to me, it would be nice if Dennis (author of
> memblock_mem_limit_remove_map) or one of the mm chaps could provide an ack
> before I merge it via arm64.
>
Will feel free to add
Acked-by: Dennis Chen <dennis.chen@arm.com>

Thanks,
Dennis
> 
> Thanks,
> 
> Will
> 
> > diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> > index 5b759c9acf97..fbfcacc50c29 100644
> > --- a/include/linux/memblock.h
> > +++ b/include/linux/memblock.h
> > @@ -333,6 +333,7 @@ phys_addr_t memblock_mem_size(unsigned long limit_pfn);
> >  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_mem_limit_remove_map(phys_addr_t limit);
> >  bool memblock_is_memory(phys_addr_t addr);
> >  int memblock_is_map_memory(phys_addr_t addr);
> > diff --git a/mm/memblock.c b/mm/memblock.c
> > index 7608bc305936..fea1688fef60 100644
> > --- a/mm/memblock.c
> > +++ b/mm/memblock.c
> > @@ -1514,11 +1514,37 @@ void __init memblock_enforce_memory_limit(phys_addr_t limit)
> >  			      (phys_addr_t)ULLONG_MAX);
> >  }
> >  
> > +void __init memblock_cap_memory_range(phys_addr_t base, phys_addr_t size)
> > +{
> > +	int start_rgn, end_rgn;
> > +	int i, ret;
> > +
> > +	if (!size)
> > +		return;
> > +
> > +	ret = memblock_isolate_range(&memblock.memory, base, size,
> > +						&start_rgn, &end_rgn);
> > +	if (ret)
> > +		return;
> > +
> > +	/* remove all the MAP regions */
> > +	for (i = memblock.memory.cnt - 1; i >= end_rgn; i--)
> > +		if (!memblock_is_nomap(&memblock.memory.regions[i]))
> > +			memblock_remove_region(&memblock.memory, i);
> > +
> > +	for (i = start_rgn - 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, base);
> > +	memblock_remove_range(&memblock.reserved,
> > +			base + size, (phys_addr_t)ULLONG_MAX);
> > +}
> > +
> >  void __init memblock_mem_limit_remove_map(phys_addr_t limit)
> >  {
> > -	struct memblock_type *type = &memblock.memory;
> >  	phys_addr_t max_addr;
> > -	int i, ret, start_rgn, end_rgn;
> >  
> >  	if (!limit)
> >  		return;
> > @@ -1529,19 +1555,7 @@ void __init memblock_mem_limit_remove_map(phys_addr_t limit)
> >  	if (max_addr == (phys_addr_t)ULLONG_MAX)
> >  		return;
> >  
> > -	ret = memblock_isolate_range(type, max_addr, (phys_addr_t)ULLONG_MAX,
> > -				&start_rgn, &end_rgn);
> > -	if (ret)
> > -		return;
> > -
> > -	/* remove all the MAP regions above the limit */
> > -	for (i = end_rgn - 1; i >= start_rgn; i--) {
> > -		if (!memblock_is_nomap(&type->regions[i]))
> > -			memblock_remove_region(type, i);
> > -	}
> > -	/* truncate the reserved regions */
> > -	memblock_remove_range(&memblock.reserved, max_addr,
> > -			      (phys_addr_t)ULLONG_MAX);
> > +	memblock_cap_memory_range(0, max_addr);
> >  }
> >  
> >  static int __init_memblock memblock_search(struct memblock_type *type, phys_addr_t addr)
> > -- 
> > 2.11.0
> > 

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