[PATCH 5.15 068/139] net: Force inlining of checksum functions in net/checksum.h

Greg Kroah-Hartman
2022-02-28T17:54:11Z

From: Christophe Leroy <christophe.leroy@csgroup.eu>

commit 5486f5bf790b5c664913076c3194b8f916a5c7ad upstream.

All functions defined as static inline in net/checksum.h are
meant to be inlined for performance reason.

But since commit ac7c3e4ff401 ("compiler: enable
CONFIG_OPTIMIZE_INLINING forcibly") the compiler is allowed to
uninline functions when it wants.

Fair enough in the general case, but for tiny performance critical
checksum helpers that's counter-productive.

The problem mainly arises when selecting CONFIG_CC_OPTIMISE_FOR_SIZE,
Those helpers being 'static inline' in header files you suddenly find
them duplicated many times in the resulting vmlinux.

Here is a typical exemple when building powerpc pmac32_defconfig
with CONFIG_CC_OPTIMISE_FOR_SIZE. csum_sub() appears 4 times:

c04a23cc <csum_sub>:
c04a23cc: 7c 84 20 f8 not r4,r4
c04a23d0: 7c 63 20 14 addc r3,r3,r4
c04a23d4: 7c 63 01 94 addze r3,r3
c04a23d8: 4e 80 00 20 blr
...
c04a2ce8: 4b ff f6 e5 bl c04a23cc <csum_sub>
...
c04a2d2c: 4b ff f6 a1 bl c04a23cc <csum_sub>
...
c04a2d54: 4b ff f6 79 bl c04a23cc <csum_sub>
...
c04a754c <csum_sub>:
c04a754c: 7c 84 20 f8 not r4,r4
c04a7550: 7c 63 20 14 addc r3,r3,r4
c04a7554: 7c 63 01 94 addze r3,r3
c04a7558: 4e 80 00 20 blr
...
c04ac930: 4b ff ac 1d bl c04a754c <csum_sub>
...
c04ad264: 4b ff a2 e9 bl c04a754c <csum_sub>
...
c04e3b08 <csum_sub>:
c04e3b08: 7c 84 20 f8 not r4,r4
c04e3b0c: 7c 63 20 14 addc r3,r3,r4
c04e3b10: 7c 63 01 94 addze r3,r3
c04e3b14: 4e 80 00 20 blr
...
c04e5788: 4b ff e3 81 bl c04e3b08 <csum_sub>
...
c04e65c8: 4b ff d5 41 bl c04e3b08 <csum_sub>
...
c0512d34 <csum_sub>:
c0512d34: 7c 84 20 f8 not r4,r4
c0512d38: 7c 63 20 14 addc r3,r3,r4
c0512d3c: 7c 63 01 94 addze r3,r3
c0512d40: 4e 80 00 20 blr
...
c0512dfc: 4b ff ff 39 bl c0512d34 <csum_sub>
...
c05138bc: 4b ff f4 79 bl c0512d34 <csum_sub>
...

Restore the expected behaviour by using __always_inline for all
functions defined in net/checksum.h

vmlinux size is even reduced by 256 bytes with this patch:

text data bss dec hex filename
6980022 2515362 194384 9689768 93daa8 vmlinux.before
6979862 2515266 194384 9689512 93d9a8 vmlinux.now

Fixes: ac7c3e4ff401 ("compiler: enable CONFIG_OPTIMIZE_INLINING forcibly")
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/checksum.h | 45 +++++++++++++++++++++++----------------------
1 file changed, 23 insertions(+), 22 deletions(-)

--- a/include/net/checksum.h
+++ b/include/net/checksum.h
@@ -22,7 +22,7 @@
#include <asm/checksum.h>

#ifndef _HAVE_ARCH_COPY_AND_CSUM_FROM_USER
-static inline
+static __always_inline
__wsum csum_and_copy_from_user (const void __user *src, void *dst,
int len)
{
@@ -33,7 +33,7 @@ __wsum csum_and_copy_from_user (const vo
#endif

#ifndef HAVE_CSUM_COPY_USER
-static __inline__ __wsum csum_and_copy_to_user
+static __always_inline __wsum csum_and_copy_to_user
(const void *src, void __user *dst, int len)
{
__wsum sum = csum_partial(src, len, ~0U);
@@ -45,7 +45,7 @@ static __inline__ __wsum csum_and_copy_t
#endif

#ifndef _HAVE_ARCH_CSUM_AND_COPY
-static inline __wsum
+static __always_inline __wsum
csum_partial_copy_nocheck(const void *src, void *dst, int len)
{
memcpy(dst, src, len);
@@ -54,7 +54,7 @@ csum_partial_copy_nocheck(const void *sr
#endif

#ifndef HAVE_ARCH_CSUM_ADD
-static inline __wsum csum_add(__wsum csum, __wsum addend)
+static __always_inline __wsum csum_add(__wsum csum, __wsum addend)
{
u32 res = (__force u32)csum;
res += (__force u32)addend;
@@ -62,12 +62,12 @@ static inline __wsum csum_add(__wsum csu
}
#endif

-static inline __wsum csum_sub(__wsum csum, __wsum addend)
+static __always_inline __wsum csum_sub(__wsum csum, __wsum addend)
{
return csum_add(csum, ~addend);
}

-static inline __sum16 csum16_add(__sum16 csum, __be16 addend)
+static __always_inline __sum16 csum16_add(__sum16 csum, __be16 addend)
{
u16 res = (__force u16)csum;

@@ -75,12 +75,12 @@ static inline __sum16 csum16_add(__sum16
return (__force __sum16)(res + (res < (__force u16)addend));
}

-static inline __sum16 csum16_sub(__sum16 csum, __be16 addend)
+static __always_inline __sum16 csum16_sub(__sum16 csum, __be16 addend)
{
return csum16_add(csum, ~addend);
}

-static inline __wsum csum_shift(__wsum sum, int offset)
+static __always_inline __wsum csum_shift(__wsum sum, int offset)
{
/* rotate sum to align it with a 16b boundary */
if (offset & 1)
@@ -88,42 +88,43 @@ static inline __wsum csum_shift(__wsum s
return sum;
}

-static inline __wsum
+static __always_inline __wsum
csum_block_add(__wsum csum, __wsum csum2, int offset)
{
return csum_add(csum, csum_shift(csum2, offset));
}

-static inline __wsum
+static __always_inline __wsum
csum_block_add_ext(__wsum csum, __wsum csum2, int offset, int len)
{
return csum_block_add(csum, csum2, offset);
}

-static inline __wsum
+static __always_inline __wsum
csum_block_sub(__wsum csum, __wsum csum2, int offset)
{
return csum_block_add(csum, ~csum2, offset);
}

-static inline __wsum csum_unfold(__sum16 n)
+static __always_inline __wsum csum_unfold(__sum16 n)
{
return (__force __wsum)n;
}

-static inline __wsum csum_partial_ext(const void *buff, int len, __wsum sum)
+static __always_inline
+__wsum csum_partial_ext(const void *buff, int len, __wsum sum)
{
return csum_partial(buff, len, sum);
}

#define CSUM_MANGLED_0 ((__force __sum16)0xffff)

-static inline void csum_replace_by_diff(__sum16 *sum, __wsum diff)
+static __always_inline void csum_replace_by_diff(__sum16 *sum, __wsum diff)
{
*sum = csum_fold(csum_add(diff, ~csum_unfold(*sum)));
}

-static inline void csum_replace4(__sum16 *sum, __be32 from, __be32 to)
+static __always_inline void csum_replace4(__sum16 *sum, __be32 from, __be32 to)
{
__wsum tmp = csum_sub(~csum_unfold(*sum), (__force __wsum)from);

@@ -136,7 +137,7 @@ static inline void csum_replace4(__sum16
* m : old value of a 16bit field
* m' : new value of a 16bit field
*/
-static inline void csum_replace2(__sum16 *sum, __be16 old, __be16 new)
+static __always_inline void csum_replace2(__sum16 *sum, __be16 old, __be16 new)
{
*sum = ~csum16_add(csum16_sub(~(*sum), old), new);
}
@@ -155,16 +156,16 @@ void inet_proto_csum_replace16(__sum16 *
void inet_proto_csum_replace_by_diff(__sum16 *sum, struct sk_buff *skb,
__wsum diff, bool pseudohdr);

-static inline void inet_proto_csum_replace2(__sum16 *sum, struct sk_buff *skb,
- __be16 from, __be16 to,
- bool pseudohdr)
+static __always_inline
+void inet_proto_csum_replace2(__sum16 *sum, struct sk_buff *skb,
+ __be16 from, __be16 to, bool pseudohdr)
{
inet_proto_csum_replace4(sum, skb, (__force __be32)from,
(__force __be32)to, pseudohdr);
}

-static inline __wsum remcsum_adjust(void *ptr, __wsum csum,
- int start, int offset)
+static __always_inline __wsum remcsum_adjust(void *ptr, __wsum csum,
+ int start, int offset)
{
__sum16 *psum = (__sum16 *)(ptr + offset);
__wsum delta;
@@ -180,7 +181,7 @@ static inline __wsum remcsum_adjust(void
return delta;
}

-static inline void remcsum_unadjust(__sum16 *psum, __wsum delta)
+static __always_inline void remcsum_unadjust(__sum16 *psum, __wsum delta)
{
*psum = csum_fold(csum_sub(delta, (__force __wsum)*psum));
}