lkml.org 
[lkml]   [2017]   [Oct]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v4 02/10] resource: add walk_system_ram_res_rev()
Hi Julien,

On Thu, Oct 05, 2017 at 10:36:47AM +0100, Julien Thierry wrote:
> Hi Takahiro,
>
> On 02/10/17 07:14, 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 | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++
> > 2 files changed, 62 insertions(+)
> >
> >diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> >index f5cf32e80041..62eb62b98118 100644
> >--- a/include/linux/ioport.h
> >+++ b/include/linux/ioport.h
> >@@ -273,6 +273,9 @@ 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..572f2f91ce9c 100644
> >--- 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>
> >@@ -469,6 +471,63 @@ 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;
>
> nit:
> Why do you need orig_end? From what I can tell it is always equal to the
> "end" parameter of the function.

Right, but all the other functions, including walk_system_ram_res()
and walk_iomem_res_desc(), use orig_end in the exact same way.

> If you think having orig_end makes it clearer to distinguish "end" from
> "res.end" could we declare it as:
>
> const u64 orig_end = end;
>
> Making it clear it is an alias?

That said, I will remove orig_end from my function.

> >+ int count, i;
> >+ int ret = -1;
> >+
> >+ count = 16; /* initial */
>
> nit:
> This doesn't represent the number of element we found but the size of the
> rams array.
> Would it be better named something like "rams_size"?

Okay

> >+
> >+ /* 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) {
> >+ /* re-alloc */
> >+ struct resource *rams_new;
> >+ int count_new;
> >+
> >+ count_new = count + 16;
> >+ rams_new = vmalloc(sizeof(struct resource) * count_new);
> >+ if (!rams_new)
> >+ goto out;
>
> Should we return -ENOMEM?

Well, I'd like to keep the current code as all the other variants just
return -1 for error.

> >+
> >+ memcpy(rams_new, rams, count);
>
> We are likely to lose data here.
>
> -> memcpy(rams_new, rams, count * sizeof(struct resourse));

Oops, thanks.

> Also, if vremalloc doesn't exist maybe the realloc part could still be put
> in a separate function?

Next time :)

Thanks,
-Takahiro AKASHI

> >+ vfree(rams);
> >+ rams = rams_new;
> >+ count = count_new;
> >+ }
> >+
> >+ 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;
> >+ }
> >+
> >+out:
> >+ vfree(rams);
> >+ return ret;
> >+}
> >+
> > #if !defined(CONFIG_ARCH_HAS_WALK_MEMORY)
> > /*
> >
>
> Cheers,
>
> --
> Julien Thierry

\
 
 \ /
  Last update: 2017-10-06 09:00    [W:0.055 / U:0.560 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site