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SubjectRe: [PATCH 03/14] resource: add walk_system_ram_res_rev()
On Thu, Aug 31, 2017 at 08:04:51AM +0530, Pratyush Anand wrote:
>
>
> 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*.

Okey, I will do that.

Thanks,
-Takahiro AKASHI

> >+ }
> >+
> >+ 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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