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SubjectRe: [PATCH 03/14] resource: add walk_system_ram_res_rev()
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On Thursday 24 August 2017 01:48 PM, AKASHI Takahiro wrote:
> This function, being a variant of walk_system_ram_res() introduced in
> commit 8c86e70acead ("resource: provide new functions to walk through
> resources"), walks through a list of all the resources of System RAM
> in reversed order, i.e., from higher to lower.
>
> It will be used in kexec_file implementation on arm64.
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> Cc: Vivek Goyal <vgoyal@redhat.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> ---
> include/linux/ioport.h | 3 +++
> kernel/resource.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 51 insertions(+)
>
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index 6230064d7f95..9a212266299f 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -271,6 +271,9 @@ extern int
> walk_system_ram_res(u64 start, u64 end, void *arg,
> int (*func)(u64, u64, void *));
> extern int
> +walk_system_ram_res_rev(u64 start, u64 end, void *arg,
> + int (*func)(u64, u64, void *));
> +extern int
> walk_iomem_res_desc(unsigned long desc, unsigned long flags, u64 start, u64 end,
> void *arg, int (*func)(u64, u64, void *));
>
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 9b5f04404152..1d6d734c75ac 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -23,6 +23,7 @@
> #include <linux/pfn.h>
> #include <linux/mm.h>
> #include <linux/resource_ext.h>
> +#include <linux/vmalloc.h>
> #include <asm/io.h>
>
>
> @@ -469,6 +470,53 @@ int walk_system_ram_res(u64 start, u64 end, void *arg,
> return ret;
> }
>
> +int walk_system_ram_res_rev(u64 start, u64 end, void *arg,
> + int (*func)(u64, u64, void *))
> +{
> + struct resource res, *rams;
> + u64 orig_end;
> + int count, i;
> + int ret = -1;
> +
> + count = 16; /* initial */
> +again:
> + /* create a list */
> + rams = vmalloc(sizeof(struct resource) * count);
> + if (!rams)
> + return ret;
> +
> + res.start = start;
> + res.end = end;
> + res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> + orig_end = res.end;
> + i = 0;
> + while ((res.start < res.end) &&
> + (!find_next_iomem_res(&res, IORES_DESC_NONE, true))) {
> + if (i >= count) {
> + /* unlikely but */
> + vfree(rams);
> + count += 16;
> + goto again;

Wounld't it be better to re-alloc a bigger space,copy previous values and free
the previous pointer, instead of going *again*.

> + }
> +
> + rams[i].start = res.start;
> + rams[i++].end = res.end;
> +
> + res.start = res.end + 1;
> + res.end = orig_end;
> + }
> +
> + /* go reverse */
> + for (i--; i >= 0; i--) {
> + ret = (*func)(rams[i].start, rams[i].end, arg);
> + if (ret)
> + break;
> + }
> +
> + vfree(rams);
> + return ret;
> +}
> +
> #if !defined(CONFIG_ARCH_HAS_WALK_MEMORY)
>
> /*
>

--
Regards
Pratyush

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