Re: [PATCH] powerpc: Use common error handling code in setup_new_fdt()

[Dan Carpenter]

On Fri, Mar 16, 2018 at 09:26:53PM +1100, Michael Ellerman wrote:
> Dan Carpenter  writes:
> > On Wed, Mar 14, 2018 at 06:22:07PM -0300, Thiago Jung Bauermann wrote:
> >> SF Markus Elfring  writes:
> >> > From: Markus Elfring 
> >> > Date: Sun, 11 Mar 2018 09:03:42 +0100
> >> >
> >> > Add a jump target so that a bit of exception handling can be better 
> >> > reused
> >> > at the end of this function.
> >> >
> >> > This issue was detected by using the Coccinelle software.
> >> >
> >> > Signed-off-by: Markus Elfring 
> >> > ---
> >> >  arch/powerpc/kernel/machine_kexec_file_64.c | 28 
> >> > 
> >> >  1 file changed, 12 insertions(+), 16 deletions(-)
> >> 
> >> I liked it. Thanks!
> >> 
> >> Reviewed-by: Thiago Jung Bauermann 
> >
> > You know that compilers already re-use string constants so this doesn't
> > actually save memory?
> 
> Sure, but it's still clearer to only have the string appear once in the
> code.
> 

To me the original was better.

> > Also we should be preserving the error codes
> > instead of always returning -EINVAL.
> 
> The error codes come from libfdt code, so they don't necessarily make
> sense in the kernel. eg. FDT_ERR_NOSPACE == 3 == ESRCH.
> 
> Perhaps we should be trying harder to convert them, but that's a
> criticism of the original code not this patch.

Ah.  You're right.  I look at the patch in context, sorry.

regards,
dan carpenter

Re: [PATCH] powerpc: Use common error handling code in setup_new_fdt()

[Michael Ellerman]

Joe Perches  writes:
> On Thu, 2018-03-15 at 14:57 +0300, Dan Carpenter wrote:
>> On Wed, Mar 14, 2018 at 06:22:07PM -0300, Thiago Jung Bauermann wrote:
>> > SF Markus Elfring  writes:
>> > > From: Markus Elfring 
>> > > Date: Sun, 11 Mar 2018 09:03:42 +0100
>> > > 
>> > > Add a jump target so that a bit of exception handling can be better 
>> > > reused
>> > > at the end of this function.
>> > > 
>> > > This issue was detected by using the Coccinelle software.
>> > > 
>> > > Signed-off-by: Markus Elfring 
>> > > ---
>> > >  arch/powerpc/kernel/machine_kexec_file_64.c | 28 
>> > > 
>> > >  1 file changed, 12 insertions(+), 16 deletions(-)
>> > 
>> > I liked it. Thanks!
>> > 
>> > Reviewed-by: Thiago Jung Bauermann 
>> 
>> You know that compilers already re-use string constants so this doesn't
>> actually save memory?
>
> And modern compilers create their own jump labels
> so this doesn't change object code either?

I must have missed the memo about us only changing source code if it
results in better object code.

cheers

Re: [PATCH] powerpc: Use common error handling code in setup_new_fdt()

[Michael Ellerman]

Dan Carpenter  writes:
> On Wed, Mar 14, 2018 at 06:22:07PM -0300, Thiago Jung Bauermann wrote:
>> SF Markus Elfring  writes:
>> > From: Markus Elfring 
>> > Date: Sun, 11 Mar 2018 09:03:42 +0100
>> >
>> > Add a jump target so that a bit of exception handling can be better reused
>> > at the end of this function.
>> >
>> > This issue was detected by using the Coccinelle software.
>> >
>> > Signed-off-by: Markus Elfring 
>> > ---
>> >  arch/powerpc/kernel/machine_kexec_file_64.c | 28 
>> > 
>> >  1 file changed, 12 insertions(+), 16 deletions(-)
>> 
>> I liked it. Thanks!
>> 
>> Reviewed-by: Thiago Jung Bauermann 
>
> You know that compilers already re-use string constants so this doesn't
> actually save memory?

Sure, but it's still clearer to only have the string appear once in the
code.

> Also we should be preserving the error codes
> instead of always returning -EINVAL.

The error codes come from libfdt code, so they don't necessarily make
sense in the kernel. eg. FDT_ERR_NOSPACE == 3 == ESRCH.

Perhaps we should be trying harder to convert them, but that's a
criticism of the original code not this patch.

cheers

Re: [PATCH] powerpc: Use common error handling code in setup_new_fdt()

[Thiago Jung Bauermann]

Joe Perches  writes:

> On Thu, 2018-03-15 at 14:57 +0300, Dan Carpenter wrote:
>> On Wed, Mar 14, 2018 at 06:22:07PM -0300, Thiago Jung Bauermann wrote:
>> > 
>> > SF Markus Elfring  writes:
>> > 
>> > > From: Markus Elfring 
>> > > Date: Sun, 11 Mar 2018 09:03:42 +0100
>> > > 
>> > > Add a jump target so that a bit of exception handling can be better 
>> > > reused
>> > > at the end of this function.
>> > > 
>> > > This issue was detected by using the Coccinelle software.
>> > > 
>> > > Signed-off-by: Markus Elfring 
>> > > ---
>> > >  arch/powerpc/kernel/machine_kexec_file_64.c | 28 
>> > > 
>> > >  1 file changed, 12 insertions(+), 16 deletions(-)
>> > 
>> > I liked it. Thanks!
>> > 
>> > Reviewed-by: Thiago Jung Bauermann 
>> > 
>> 
>> You know that compilers already re-use string constants so this doesn't
>> actually save memory?
>
> And modern compilers create their own jump labels
> so this doesn't change object code either?

IMHO it's an improvement to the source code itself. I wasn't thinking
about the object file.

-- 
Thiago Jung Bauermann
IBM Linux Technology Center

Re: [PATCH] powerpc: Use common error handling code in setup_new_fdt()

[Dan Carpenter]

On Wed, Mar 14, 2018 at 06:22:07PM -0300, Thiago Jung Bauermann wrote:
> 
> SF Markus Elfring  writes:
> 
> > From: Markus Elfring 
> > Date: Sun, 11 Mar 2018 09:03:42 +0100
> >
> > Add a jump target so that a bit of exception handling can be better reused
> > at the end of this function.
> >
> > This issue was detected by using the Coccinelle software.
> >
> > Signed-off-by: Markus Elfring 
> > ---
> >  arch/powerpc/kernel/machine_kexec_file_64.c | 28 
> > 
> >  1 file changed, 12 insertions(+), 16 deletions(-)
> 
> I liked it. Thanks!
> 
> Reviewed-by: Thiago Jung Bauermann 
> 

You know that compilers already re-use string constants so this doesn't
actually save memory?  Also we should be preserving the error codes
instead of always returning -EINVAL.

regards,
dan carpenter

Re: [PATCH] powerpc: Use common error handling code in setup_new_fdt()

[Joe Perches]

On Thu, 2018-03-15 at 14:57 +0300, Dan Carpenter wrote:
> On Wed, Mar 14, 2018 at 06:22:07PM -0300, Thiago Jung Bauermann wrote:
> > 
> > SF Markus Elfring  writes:
> > 
> > > From: Markus Elfring 
> > > Date: Sun, 11 Mar 2018 09:03:42 +0100
> > > 
> > > Add a jump target so that a bit of exception handling can be better reused
> > > at the end of this function.
> > > 
> > > This issue was detected by using the Coccinelle software.
> > > 
> > > Signed-off-by: Markus Elfring 
> > > ---
> > >  arch/powerpc/kernel/machine_kexec_file_64.c | 28 
> > > 
> > >  1 file changed, 12 insertions(+), 16 deletions(-)
> > 
> > I liked it. Thanks!
> > 
> > Reviewed-by: Thiago Jung Bauermann 
> > 
> 
> You know that compilers already re-use string constants so this doesn't
> actually save memory?

And modern compilers create their own jump labels
so this doesn't change object code either?

Re: [PATCH] powerpc: Use common error handling code in setup_new_fdt()

[Thiago Jung Bauermann]

SF Markus Elfring  writes:

> From: Markus Elfring 
> Date: Sun, 11 Mar 2018 09:03:42 +0100
>
> Add a jump target so that a bit of exception handling can be better reused
> at the end of this function.
>
> This issue was detected by using the Coccinelle software.
>
> Signed-off-by: Markus Elfring 
> ---
>  arch/powerpc/kernel/machine_kexec_file_64.c | 28 
>  1 file changed, 12 insertions(+), 16 deletions(-)

I liked it. Thanks!

Reviewed-by: Thiago Jung Bauermann 

-- 
Thiago Jung Bauermann
IBM Linux Technology Center

[PATCH] powerpc: Use common error handling code in setup_new_fdt()

[SF Markus Elfring]

From: Markus Elfring 
Date: Sun, 11 Mar 2018 09:03:42 +0100

Add a jump target so that a bit of exception handling can be better reused
at the end of this function.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring 
---
 arch/powerpc/kernel/machine_kexec_file_64.c | 28 
 1 file changed, 12 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/kernel/machine_kexec_file_64.c 
b/arch/powerpc/kernel/machine_kexec_file_64.c
index e4395f937d63..90c6004c2eec 100644
--- a/arch/powerpc/kernel/machine_kexec_file_64.c
+++ b/arch/powerpc/kernel/machine_kexec_file_64.c
@@ -302,18 +302,14 @@ int setup_new_fdt(const struct kimage *image, void *fdt,
ret = fdt_setprop_u64(fdt, chosen_node,
  "linux,initrd-start",
  initrd_load_addr);
-   if (ret < 0) {
-   pr_err("Error setting up the new device tree.\n");
-   return -EINVAL;
-   }
+   if (ret < 0)
+   goto report_setup_failure;
 
/* initrd-end is the first address after the initrd image. */
ret = fdt_setprop_u64(fdt, chosen_node, "linux,initrd-end",
  initrd_load_addr + initrd_len);
-   if (ret < 0) {
-   pr_err("Error setting up the new device tree.\n");
-   return -EINVAL;
-   }
+   if (ret < 0)
+   goto report_setup_failure;
 
ret = fdt_add_mem_rsv(fdt, initrd_load_addr, initrd_len);
if (ret) {
@@ -325,10 +321,8 @@ int setup_new_fdt(const struct kimage *image, void *fdt,
 
if (cmdline != NULL) {
ret = fdt_setprop_string(fdt, chosen_node, "bootargs", cmdline);
-   if (ret < 0) {
-   pr_err("Error setting up the new device tree.\n");
-   return -EINVAL;
-   }
+   if (ret < 0)
+   goto report_setup_failure;
} else {
ret = fdt_delprop(fdt, chosen_node, "bootargs");
if (ret && ret != -FDT_ERR_NOTFOUND) {
@@ -344,10 +338,12 @@ int setup_new_fdt(const struct kimage *image, void *fdt,
}
 
ret = fdt_setprop(fdt, chosen_node, "linux,booted-from-kexec", NULL, 0);
-   if (ret) {
-   pr_err("Error setting up the new device tree.\n");
-   return -EINVAL;
-   }
+   if (ret)
+   goto report_setup_failure;
 
return 0;
+
+report_setup_failure:
+   pr_err("Error setting up the new device tree.\n");
+   return -EINVAL;
 }
-- 
2.16.2