Patchwork [RESEND,1/2] lib/scatterlist: Make ARCH_HAS_SG_CHAIN an actual Kconfig

login
register
mail settings
Submitter Laura Abbott
Date March 22, 2014, 6:13 p.m.
Message ID <1395512032-20575-2-git-send-email-lauraa@codeaurora.org>
Download mbox | patch
Permalink /patch/332845/
State Not Applicable
Headers show

Comments

Laura Abbott - March 22, 2014, 6:13 p.m.
Rather than have architectures #define ARCH_HAS_SG_CHAIN in an architecture
specific scatterlist.h, make it a proper Kconfig option and use that
instead. At same time, remove the header files are are now mostly
useless and just include asm-generic/scatterlist.h.

Cc: Russell King <linux@arm.linux.org.uk>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
---
 arch/arm/Kconfig                       |  1 +
 arch/arm/include/asm/Kbuild            |  1 +
 arch/arm/include/asm/scatterlist.h     | 12 ------------
 arch/arm64/Kconfig                     |  1 +
 arch/ia64/Kconfig                      |  1 +
 arch/ia64/include/asm/Kbuild           |  1 +
 arch/ia64/include/asm/scatterlist.h    |  7 -------
 arch/powerpc/Kconfig                   |  1 +
 arch/powerpc/include/asm/Kbuild        |  1 +
 arch/powerpc/include/asm/scatterlist.h | 17 -----------------
 arch/s390/Kconfig                      |  1 +
 arch/s390/include/asm/Kbuild           |  1 +
 arch/s390/include/asm/scatterlist.h    |  3 ---
 arch/sparc/Kconfig                     |  1 +
 arch/sparc/include/asm/Kbuild          |  1 +
 arch/sparc/include/asm/scatterlist.h   |  8 --------
 arch/x86/Kconfig                       |  1 +
 arch/x86/include/asm/Kbuild            |  1 +
 arch/x86/include/asm/scatterlist.h     |  8 --------
 include/linux/scatterlist.h            |  2 +-
 include/scsi/scsi.h                    |  2 +-
 lib/Kconfig                            |  7 +++++++
 lib/scatterlist.c                      |  4 ++--
 23 files changed, 24 insertions(+), 59 deletions(-)
 delete mode 100644 arch/arm/include/asm/scatterlist.h
 delete mode 100644 arch/ia64/include/asm/scatterlist.h
 delete mode 100644 arch/powerpc/include/asm/scatterlist.h
 delete mode 100644 arch/s390/include/asm/scatterlist.h
 delete mode 100644 arch/sparc/include/asm/scatterlist.h
 delete mode 100644 arch/x86/include/asm/scatterlist.h
Thomas Gleixner - March 22, 2014, 8:44 p.m.
On Sat, 22 Mar 2014, Laura Abbott wrote:

> Rather than have architectures #define ARCH_HAS_SG_CHAIN in an architecture
> specific scatterlist.h, make it a proper Kconfig option and use that
> instead. At same time, remove the header files are are now mostly
> useless and just include asm-generic/scatterlist.h.
> 
> Cc: Russell King <linux@arm.linux.org.uk>
> Cc: Tony Luck <tony.luck@intel.com>
> Cc: Fenghua Yu <fenghua.yu@intel.com>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
> Cc: Fenghua Yu <fenghua.yu@intel.com>
> Cc: Tony Luck <tony.luck@intel.com>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Laura Abbott <lauraa@codeaurora.org>

For the x86 part:

Acked-by: Thomas Gleixner <tglx@linutronix.de>
James Bottomley - March 22, 2014, 9:31 p.m.
On Sat, 2014-03-22 at 11:13 -0700, Laura Abbott wrote:
> Rather than have architectures #define ARCH_HAS_SG_CHAIN in an architecture
> specific scatterlist.h, make it a proper Kconfig option and use that
> instead. At same time, remove the header files are are now mostly
> useless and just include asm-generic/scatterlist.h.

Well, the transformation looks fine.  Perhaps part of the reason for the
lack of response is that there's no compelling reason in the change log
above for doing this.  The usual reason for eliminating ARCH_HAS is that
it's hiding something that would be better expressed a different way
(that's actually intuitive to grep) or that it's expressing something
that should be configurable.  Neither of these reasons apply in this
case, because SG_CHAIN definitely is a property of the architecture not
the config space and it's not really hiding anything.

Perhaps now might be the time to ask which are the remaining
architectures that cannot do SG chaining and then we can fix them and
pull the whole thing out.

James
Thomas Gleixner - March 22, 2014, 10:03 p.m.
On Sat, 22 Mar 2014, James Bottomley wrote:

> On Sat, 2014-03-22 at 11:13 -0700, Laura Abbott wrote:
> > Rather than have architectures #define ARCH_HAS_SG_CHAIN in an architecture
> > specific scatterlist.h, make it a proper Kconfig option and use that
> > instead. At same time, remove the header files are are now mostly
> > useless and just include asm-generic/scatterlist.h.
> 
> Well, the transformation looks fine.  Perhaps part of the reason for the
> lack of response is that there's no compelling reason in the change log
> above for doing this.  The usual reason for eliminating ARCH_HAS is that
> it's hiding something that would be better expressed a different way
> (that's actually intuitive to grep) or that it's expressing something
> that should be configurable.  Neither of these reasons apply in this
> case, because SG_CHAIN definitely is a property of the architecture not
> the config space and it's not really hiding anything.

Getting rid of pointless copied code is definitely a good enough
reason and the patch removes quite some of that.
 
Thanks,

	tglx
Russell King - ARM Linux - March 22, 2014, 10:23 p.m.
On Sat, Mar 22, 2014 at 02:31:21PM -0700, James Bottomley wrote:
> Perhaps now might be the time to ask which are the remaining
> architectures that cannot do SG chaining and then we can fix them and
> pull the whole thing out.

Not quite.  You're making the assumption that we can be sure that all
the scatterlist users on an architecture have been converted - that's
simply not true on ARM.  We have some which have, and some which still
have not been audited.

The cases that get us here would be old platform DMA code which walks
scatterlists handed to it from drivers - stuff like
arch/arm/mach-rpc/dma.c (which probably can cope), and drivers/scsi/arm/*
(which definitely can't because of their SCSI pointers save/restore
handling message.)  I know that's one case where SG_CHAIN definitely
isn't supported on ARM.

So, we had decided not to enable it, but this means that new stuff
isn't benefitting from this.  I've recently asked arm-soc to enable
it for the modern multi-platform builds, because modern stuff really
be written with correct SG chaining in mind.
James Bottomley - March 22, 2014, 10:37 p.m.
On Sat, 2014-03-22 at 22:23 +0000, Russell King - ARM Linux wrote:
> On Sat, Mar 22, 2014 at 02:31:21PM -0700, James Bottomley wrote:
> > Perhaps now might be the time to ask which are the remaining
> > architectures that cannot do SG chaining and then we can fix them and
> > pull the whole thing out.
> 
> Not quite.  You're making the assumption that we can be sure that all
> the scatterlist users on an architecture have been converted - that's
> simply not true on ARM.

No I'm not, I said "now might be the time to ask which are the remaining
architectures that cannot do SG chaining" I think it's time to list them
so we know what work remains.  I know we've got a bunch in parisc (all
of our iommu code in driver/parisc - about 5 different ones - are
unconverted).  However, the conversion is pretty simple; it's mostly
replacing sglist++ with sglist=sg_next(sglist)

>   We have some which have, and some which still
> have not been audited.
> 
> The cases that get us here would be old platform DMA code which walks
> scatterlists handed to it from drivers - stuff like
> arch/arm/mach-rpc/dma.c (which probably can cope), and drivers/scsi/arm/*
> (which definitely can't because of their SCSI pointers save/restore
> handling message.)  I know that's one case where SG_CHAIN definitely
> isn't supported on ARM.
> 
> So, we had decided not to enable it, but this means that new stuff
> isn't benefitting from this.  I've recently asked arm-soc to enable
> it for the modern multi-platform builds, because modern stuff really
> be written with correct SG chaining in mind.

OK, so lets see what the actual effort is.

James
Russell King - ARM Linux - March 22, 2014, 10:52 p.m.
On Sat, Mar 22, 2014 at 03:37:40PM -0700, James Bottomley wrote:
> On Sat, 2014-03-22 at 22:23 +0000, Russell King - ARM Linux wrote:
> > On Sat, Mar 22, 2014 at 02:31:21PM -0700, James Bottomley wrote:
> > > Perhaps now might be the time to ask which are the remaining
> > > architectures that cannot do SG chaining and then we can fix them and
> > > pull the whole thing out.
> > 
> > Not quite.  You're making the assumption that we can be sure that all
> > the scatterlist users on an architecture have been converted - that's
> > simply not true on ARM.
> 
> No I'm not, I said "now might be the time to ask which are the remaining
> architectures that cannot do SG chaining"

And I'm disagreeing with that statement which implies that it's something
that is an architecture wide property for any particular architecture.

Right now in mainline, if ARM has IOMMU support enabled, then SG_CHAIN
support will also be enabled.  I've a patch out of tree which I've been
using for years which enables SG_CHAIN for a particular SoC (Dove).
Otherwise, it doesn't have support for SG_CHAIN.

PARISC on the other hand (as you list) has no support to enable SG_CHAIN
under any circumstances.

Where we're disagreeing is whether this is something that is always-on or
always-off for any particular architecture.
James Bottomley - March 22, 2014, 10:59 p.m.
On Sat, 2014-03-22 at 22:52 +0000, Russell King - ARM Linux wrote:
> On Sat, Mar 22, 2014 at 03:37:40PM -0700, James Bottomley wrote:
> > On Sat, 2014-03-22 at 22:23 +0000, Russell King - ARM Linux wrote:
> > > On Sat, Mar 22, 2014 at 02:31:21PM -0700, James Bottomley wrote:
> > > > Perhaps now might be the time to ask which are the remaining
> > > > architectures that cannot do SG chaining and then we can fix them and
> > > > pull the whole thing out.
> > > 
> > > Not quite.  You're making the assumption that we can be sure that all
> > > the scatterlist users on an architecture have been converted - that's
> > > simply not true on ARM.
> > 
> > No I'm not, I said "now might be the time to ask which are the remaining
> > architectures that cannot do SG chaining"
> 
> And I'm disagreeing with that statement which implies that it's something
> that is an architecture wide property for any particular architecture.
> 
> Right now in mainline, if ARM has IOMMU support enabled, then SG_CHAIN
> support will also be enabled.  I've a patch out of tree which I've been
> using for years which enables SG_CHAIN for a particular SoC (Dove).
> Otherwise, it doesn't have support for SG_CHAIN.
> 
> PARISC on the other hand (as you list) has no support to enable SG_CHAIN
> under any circumstances.
> 
> Where we're disagreeing is whether this is something that is always-on or
> always-off for any particular architecture.

Actually, I don't disagree with that.  PA used to share sb_iommu with
ia64 (it's the same chipset for the HP versions), but we can't now
because ia64 is chained and we're not and there's no way to say chained
for this platform but not for these other more legacy ones.  If you have
a proposal for this, I'd be interested, so I don't have to do an all or
nothing conversion, but the config option isn't it because our platform
configuration is runtime determined (we usually select every driver and
let the actual one be chosen at runtime from the config table).

James
Benjamin Herrenschmidt - March 23, 2014, 3:04 a.m.
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 1594945..8122294 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -82,6 +82,7 @@ config ARM
>  	  <http://www.arm.linux.org.uk/>.
>  
>  config ARM_HAS_SG_CHAIN
> +	select ARCH_HAS_SG_CHAIN
>  	bool
>  

Heh, a self-selecting config option... I didn't know that trick !

Ben.
Benjamin Herrenschmidt - March 23, 2014, 3:06 a.m.
On Sat, 2014-03-22 at 11:13 -0700, Laura Abbott wrote:
> Rather than have architectures #define ARCH_HAS_SG_CHAIN in an architecture
> specific scatterlist.h, make it a proper Kconfig option and use that
> instead. At same time, remove the header files are are now mostly
> useless and just include asm-generic/scatterlist.h.
> 
> Cc: Russell King <linux@arm.linux.org.uk>
> Cc: Tony Luck <tony.luck@intel.com>
> Cc: Fenghua Yu <fenghua.yu@intel.com>

For powerpc

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
> Cc: Fenghua Yu <fenghua.yu@intel.com>
> Cc: Tony Luck <tony.luck@intel.com>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
Christoph Hellwig - March 23, 2014, 7:03 a.m.
On Sun, Mar 23, 2014 at 02:04:46PM +1100, Benjamin Herrenschmidt wrote:
> 
> > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > index 1594945..8122294 100644
> > --- a/arch/arm/Kconfig
> > +++ b/arch/arm/Kconfig
> > @@ -82,6 +82,7 @@ config ARM
> >  	  <http://www.arm.linux.org.uk/>.
> >  
> >  config ARM_HAS_SG_CHAIN
> > +	select ARCH_HAS_SG_CHAIN
> >  	bool
> >  
> 
> Heh, a self-selecting config option... I didn't know that trick !

ARM vs ARCH.  However the arm variant of the variable should probably be
consolidated into the ARCH one as a follow up.
Benjamin Herrenschmidt - March 23, 2014, 8:58 a.m.
On Sun, 2014-03-23 at 00:03 -0700, Christoph Hellwig wrote:
> On Sun, Mar 23, 2014 at 02:04:46PM +1100, Benjamin Herrenschmidt wrote:
> > 
> > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > > index 1594945..8122294 100644
> > > --- a/arch/arm/Kconfig
> > > +++ b/arch/arm/Kconfig
> > > @@ -82,6 +82,7 @@ config ARM
> > >  	  <http://www.arm.linux.org.uk/>.
> > >  
> > >  config ARM_HAS_SG_CHAIN
> > > +	select ARCH_HAS_SG_CHAIN
> > >  	bool
> > >  
> > 
> > Heh, a self-selecting config option... I didn't know that trick !
> 
> ARM vs ARCH.  However the arm variant of the variable should probably be
> consolidated into the ARCH one as a follow up.

Oh right... sorry for the noise.

Ben.
Heiko Carstens - March 24, 2014, 5:47 a.m.
On Sat, Mar 22, 2014 at 11:13:51AM -0700, Laura Abbott wrote:
> Rather than have architectures #define ARCH_HAS_SG_CHAIN in an architecture
> specific scatterlist.h, make it a proper Kconfig option and use that
> instead. At same time, remove the header files are are now mostly
> useless and just include asm-generic/scatterlist.h.
> 

[...]

> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index 65a0775..d6c2059 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -142,6 +142,7 @@ config S390
>  	select SYSCTL_EXCEPTION_TRACE
>  	select VIRT_CPU_ACCOUNTING
>  	select VIRT_TO_BUS
> +	select ARCH_HAS_SG_CHAIN
> 

Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>

FWIW, it would have been nice to keep the list of selected configs sorted.
However no need to resend.
Russell King - ARM Linux - March 24, 2014, 10:45 a.m.
On Sat, Mar 22, 2014 at 03:59:11PM -0700, James Bottomley wrote:
> On Sat, 2014-03-22 at 22:52 +0000, Russell King - ARM Linux wrote:
> > And I'm disagreeing with that statement which implies that it's something
> > that is an architecture wide property for any particular architecture.
> > 
> > Right now in mainline, if ARM has IOMMU support enabled, then SG_CHAIN
> > support will also be enabled.  I've a patch out of tree which I've been
> > using for years which enables SG_CHAIN for a particular SoC (Dove).
> > Otherwise, it doesn't have support for SG_CHAIN.
> > 
> > PARISC on the other hand (as you list) has no support to enable SG_CHAIN
> > under any circumstances.
> > 
> > Where we're disagreeing is whether this is something that is always-on or
> > always-off for any particular architecture.
> 
> Actually, I don't disagree with that.  PA used to share sb_iommu with
> ia64 (it's the same chipset for the HP versions), but we can't now
> because ia64 is chained and we're not and there's no way to say chained
> for this platform but not for these other more legacy ones.  If you have
> a proposal for this, I'd be interested, so I don't have to do an all or
> nothing conversion, but the config option isn't it because our platform
> configuration is runtime determined (we usually select every driver and
> let the actual one be chosen at runtime from the config table).

At runtime, it's obviously a lot harder to resolve.  However, that's not
what we're trying to do with this patch.

The main issue is that Laura is trying to add SG chain support to ARM64.
At the moment, ARM64 uses the asm-generic version of scatterlist.h
directly.

Her first spin of the patch involved creating
arch/arm64/include/asm/scatterlist.h, which was nothing more than an
include of the asm-generic header file of the same name, and the
definition of ARCH_HAS_SG_CHAIN.  That seemed to be extremely wasteful
and sub-optimal way to handle this.

Moving this symbol into the Kconfig means that ARM64 no longer has to
have this additional file (and probably a bunch of other architectures
fall into that same camp) and the ARM specific CONFIG_ARM_HAS_SG_CHAIN
can be eliminated in favour of the now generic cross-arch config symbol.

We have plenty of other Kconfig symbols which control similar features
throughout the kernel source, there is no reason that this one should
not be the same.

Patch

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 1594945..8122294 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -82,6 +82,7 @@  config ARM
 	  <http://www.arm.linux.org.uk/>.
 
 config ARM_HAS_SG_CHAIN
+	select ARCH_HAS_SG_CHAIN
 	bool
 
 config NEED_SG_DMA_LENGTH
diff --git a/arch/arm/include/asm/Kbuild b/arch/arm/include/asm/Kbuild
index 3278afe..2357ed6 100644
--- a/arch/arm/include/asm/Kbuild
+++ b/arch/arm/include/asm/Kbuild
@@ -18,6 +18,7 @@  generic-y += param.h
 generic-y += parport.h
 generic-y += poll.h
 generic-y += resource.h
+generic-y += scatterlist.h
 generic-y += sections.h
 generic-y += segment.h
 generic-y += sembuf.h
diff --git a/arch/arm/include/asm/scatterlist.h b/arch/arm/include/asm/scatterlist.h
deleted file mode 100644
index cefdb8f..0000000
--- a/arch/arm/include/asm/scatterlist.h
+++ /dev/null
@@ -1,12 +0,0 @@ 
-#ifndef _ASMARM_SCATTERLIST_H
-#define _ASMARM_SCATTERLIST_H
-
-#ifdef CONFIG_ARM_HAS_SG_CHAIN
-#define ARCH_HAS_SG_CHAIN
-#endif
-
-#include <asm/memory.h>
-#include <asm/types.h>
-#include <asm-generic/scatterlist.h>
-
-#endif /* _ASMARM_SCATTERLIST_H */
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 27bbcfc..f2f95f4 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -2,6 +2,7 @@  config ARM64
 	def_bool y
 	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	select ARCH_USE_CMPXCHG_LOCKREF
+	select ARCH_HAS_SG_CHAIN
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_WANT_OPTIONAL_GPIOLIB
 	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
index 0c8e553..13e2e8b 100644
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig
@@ -44,6 +44,7 @@  config IA64
 	select HAVE_MOD_ARCH_SPECIFIC
 	select MODULES_USE_ELF_RELA
 	select ARCH_USE_CMPXCHG_LOCKREF
+	select ARCH_HAS_SG_CHAIN
 	default y
 	help
 	  The Itanium Processor Family is Intel's 64-bit successor to
diff --git a/arch/ia64/include/asm/Kbuild b/arch/ia64/include/asm/Kbuild
index 283a831..3906865 100644
--- a/arch/ia64/include/asm/Kbuild
+++ b/arch/ia64/include/asm/Kbuild
@@ -2,6 +2,7 @@ 
 generic-y += clkdev.h
 generic-y += exec.h
 generic-y += kvm_para.h
+generic-y += scatterlist.h
 generic-y += trace_clock.h
 generic-y += preempt.h
 generic-y += vtime.h
diff --git a/arch/ia64/include/asm/scatterlist.h b/arch/ia64/include/asm/scatterlist.h
deleted file mode 100644
index 08fd93b..0000000
--- a/arch/ia64/include/asm/scatterlist.h
+++ /dev/null
@@ -1,7 +0,0 @@ 
-#ifndef _ASM_IA64_SCATTERLIST_H
-#define _ASM_IA64_SCATTERLIST_H
-
-#include <asm-generic/scatterlist.h>
-#define ARCH_HAS_SG_CHAIN
-
-#endif /* _ASM_IA64_SCATTERLIST_H */
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 957bf34..659aee2 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -141,6 +141,7 @@  config PPC
 	select HAVE_DEBUG_STACKOVERFLOW
 	select HAVE_IRQ_EXIT_ON_IRQ_STACK
 	select ARCH_USE_CMPXCHG_LOCKREF if PPC64
+	select ARCH_HAS_SG_CHAIN
 
 config GENERIC_CSUM
 	def_bool CPU_LITTLE_ENDIAN
diff --git a/arch/powerpc/include/asm/Kbuild b/arch/powerpc/include/asm/Kbuild
index 6c0a955..ca596ec 100644
--- a/arch/powerpc/include/asm/Kbuild
+++ b/arch/powerpc/include/asm/Kbuild
@@ -1,6 +1,7 @@ 
 
 generic-y += clkdev.h
 generic-y += rwsem.h
+generic-y += scatterlist.h
 generic-y += trace_clock.h
 generic-y += preempt.h
 generic-y += vtime.h
diff --git a/arch/powerpc/include/asm/scatterlist.h b/arch/powerpc/include/asm/scatterlist.h
deleted file mode 100644
index de1f620..0000000
--- a/arch/powerpc/include/asm/scatterlist.h
+++ /dev/null
@@ -1,17 +0,0 @@ 
-#ifndef _ASM_POWERPC_SCATTERLIST_H
-#define _ASM_POWERPC_SCATTERLIST_H
-/*
- * Copyright (C) 2001 PPC64 Team, IBM Corp
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version
- * 2 of the License, or (at your option) any later version.
- */
-
-#include <asm/dma.h>
-#include <asm-generic/scatterlist.h>
-
-#define ARCH_HAS_SG_CHAIN
-
-#endif /* _ASM_POWERPC_SCATTERLIST_H */
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 65a0775..d6c2059 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -142,6 +142,7 @@  config S390
 	select SYSCTL_EXCEPTION_TRACE
 	select VIRT_CPU_ACCOUNTING
 	select VIRT_TO_BUS
+	select ARCH_HAS_SG_CHAIN
 
 config SCHED_OMIT_FRAME_POINTER
 	def_bool y
diff --git a/arch/s390/include/asm/Kbuild b/arch/s390/include/asm/Kbuild
index 8386a4a..14be6d0 100644
--- a/arch/s390/include/asm/Kbuild
+++ b/arch/s390/include/asm/Kbuild
@@ -4,3 +4,4 @@  generic-y += clkdev.h
 generic-y += trace_clock.h
 generic-y += preempt.h
 generic-y += hash.h
+generic-y += scatterlist.h
diff --git a/arch/s390/include/asm/scatterlist.h b/arch/s390/include/asm/scatterlist.h
deleted file mode 100644
index 6d45ef6..0000000
--- a/arch/s390/include/asm/scatterlist.h
+++ /dev/null
@@ -1,3 +0,0 @@ 
-#include <asm-generic/scatterlist.h>
-
-#define ARCH_HAS_SG_CHAIN
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 7d8b7e9..7a179fe 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -42,6 +42,7 @@  config SPARC
 	select MODULES_USE_ELF_RELA
 	select ODD_RT_SIGACTION
 	select OLD_SIGSUSPEND
+	select ARCH_HAS_SG_CHAIN
 
 config SPARC32
 	def_bool !64BIT
diff --git a/arch/sparc/include/asm/Kbuild b/arch/sparc/include/asm/Kbuild
index 4b60a0c..437f0c6 100644
--- a/arch/sparc/include/asm/Kbuild
+++ b/arch/sparc/include/asm/Kbuild
@@ -18,3 +18,4 @@  generic-y += types.h
 generic-y += word-at-a-time.h
 generic-y += preempt.h
 generic-y += hash.h
+generic-y += scatterlist.h
diff --git a/arch/sparc/include/asm/scatterlist.h b/arch/sparc/include/asm/scatterlist.h
deleted file mode 100644
index 92bb638..0000000
--- a/arch/sparc/include/asm/scatterlist.h
+++ /dev/null
@@ -1,8 +0,0 @@ 
-#ifndef _SPARC_SCATTERLIST_H
-#define _SPARC_SCATTERLIST_H
-
-#include <asm-generic/scatterlist.h>
-
-#define ARCH_HAS_SG_CHAIN
-
-#endif /* !(_SPARC_SCATTERLIST_H) */
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 0af5250..76997dc 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -127,6 +127,7 @@  config X86
 	select HAVE_DEBUG_STACKOVERFLOW
 	select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
 	select HAVE_CC_STACKPROTECTOR
+	select ARCH_HAS_SG_CHAIN
 
 config INSTRUCTION_DECODER
 	def_bool y
diff --git a/arch/x86/include/asm/Kbuild b/arch/x86/include/asm/Kbuild
index 7f66985..9b3d749 100644
--- a/arch/x86/include/asm/Kbuild
+++ b/arch/x86/include/asm/Kbuild
@@ -5,3 +5,4 @@  genhdr-y += unistd_64.h
 genhdr-y += unistd_x32.h
 
 generic-y += clkdev.h
+generic-y += scatterlist.h
diff --git a/arch/x86/include/asm/scatterlist.h b/arch/x86/include/asm/scatterlist.h
deleted file mode 100644
index 4240878..0000000
--- a/arch/x86/include/asm/scatterlist.h
+++ /dev/null
@@ -1,8 +0,0 @@ 
-#ifndef _ASM_X86_SCATTERLIST_H
-#define _ASM_X86_SCATTERLIST_H
-
-#include <asm-generic/scatterlist.h>
-
-#define ARCH_HAS_SG_CHAIN
-
-#endif /* _ASM_X86_SCATTERLIST_H */
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index a964f72..4b152c8 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -136,7 +136,7 @@  static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
 static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
 			    struct scatterlist *sgl)
 {
-#ifndef ARCH_HAS_SG_CHAIN
+#ifndef CONFIG_ARCH_HAS_SG_CHAIN
 	BUG();
 #endif
 
diff --git a/include/scsi/scsi.h b/include/scsi/scsi.h
index 0a4edfe..d34cf2d 100644
--- a/include/scsi/scsi.h
+++ b/include/scsi/scsi.h
@@ -31,7 +31,7 @@  enum scsi_timeouts {
  * Like SCSI_MAX_SG_SEGMENTS, but for archs that have sg chaining. This limit
  * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
  */
-#ifdef ARCH_HAS_SG_CHAIN
+#ifdef CONFIG_ARCH_HAS_SG_CHAIN
 #define SCSI_MAX_SG_CHAIN_SEGMENTS	2048
 #else
 #define SCSI_MAX_SG_CHAIN_SEGMENTS	SCSI_MAX_SG_SEGMENTS
diff --git a/lib/Kconfig b/lib/Kconfig
index 991c98b..32c68d3 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -451,4 +451,11 @@  config UCS2_STRING
 
 source "lib/fonts/Kconfig"
 
+#
+# sg chaining option
+#
+
+config ARCH_HAS_SG_CHAIN
+	def_bool n
+
 endmenu
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 3a8e8e8..4251cbd 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -73,7 +73,7 @@  EXPORT_SYMBOL(sg_nents);
  **/
 struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents)
 {
-#ifndef ARCH_HAS_SG_CHAIN
+#ifndef CONFIG_ARCH_HAS_SG_CHAIN
 	struct scatterlist *ret = &sgl[nents - 1];
 #else
 	struct scatterlist *sg, *ret = NULL;
@@ -251,7 +251,7 @@  int __sg_alloc_table(struct sg_table *table, unsigned int nents,
 
 	if (nents == 0)
 		return -EINVAL;
-#ifndef ARCH_HAS_SG_CHAIN
+#ifndef CONFIG_ARCH_HAS_SG_CHAIN
 	if (WARN_ON_ONCE(nents > max_ents))
 		return -EINVAL;
 #endif