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SubjectRe: [PATCH 1/2] resource: add walk_system_ram_res_rev()
On Thu, 22 Mar 2018 11:37:21 +0800 Baoquan He <bhe@redhat.com> wrote:

> From: AKASHI Takahiro <takahiro.akashi@linaro.org>
>
> 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 code.
>
> ...
>
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -23,6 +23,8 @@
> #include <linux/pfn.h>
> #include <linux/mm.h>
> #include <linux/resource_ext.h>
> +#include <linux/string.h>
> +#include <linux/vmalloc.h>
> #include <asm/io.h>
>
>
> @@ -470,6 +472,67 @@ int walk_system_ram_res(u64 start, u64 end, void *arg,
> }
>
> /*
> + * This function, being a variant of walk_system_ram_res(), calls the @func
> + * callback against all memory ranges of type System RAM which are marked as
> + * IORESOURCE_SYSTEM_RAM and IORESOUCE_BUSY in reversed order, i.e., from
> + * higher to lower.
> + */

This should document the return value, as should walk_system_ram_res().
Why does it return -1 on error rather than an errno (ENOMEM)?

> +int walk_system_ram_res_rev(u64 start, u64 end, void *arg,
> + int (*func)(struct resource *, void *))
> +{
> + struct resource res, *rams;
> + int rams_size = 16, i;
> + int ret = -1;
> +
> + /* create a list */
> + rams = vmalloc(sizeof(struct resource) * rams_size);
> + if (!rams)
> + return ret;
> +
> + res.start = start;
> + res.end = end;
> + res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> + i = 0;
> + while ((res.start < res.end) &&
> + (!find_next_iomem_res(&res, IORES_DESC_NONE, true))) {
> + if (i >= rams_size) {
> + /* re-alloc */
> + struct resource *rams_new;
> + int rams_new_size;
> +
> + rams_new_size = rams_size + 16;
> + rams_new = vmalloc(sizeof(struct resource)
> + * rams_new_size);
> + if (!rams_new)
> + goto out;
> +
> + memcpy(rams_new, rams,
> + sizeof(struct resource) * rams_size);
> + vfree(rams);
> + rams = rams_new;
> + rams_size = rams_new_size;
> + }
> +
> + rams[i].start = res.start;
> + rams[i++].end = res.end;
> +
> + res.start = res.end + 1;
> + res.end = end;
> + }
> +
> + /* go reverse */
> + for (i--; i >= 0; i--) {
> + ret = (*func)(&rams[i], arg);
> + if (ret)
> + break;
> + }

erk, this is pretty nasty. Isn't there a better way :(

> +out:
> + vfree(rams);
> + return ret;
> +}

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