[PATCH v3] Consolidate Linux readahead() implementations

[Yury Norov <ynorov at caviumnetworks dot com>]

There are 4 different implementations of readahead() in glibc:
 - arm and mips32 use one located under sysdeps/unix/sysv/linux/arm;
 - powerpc32 and wordsize64 has 2 another  implementations in their
   syscalls.list;
 - and there's generic implementation under sysdeps/unix/sysv/linux for
   other ports.

With the [1] it's possible to consolidate all of them except tile32
under sysdeps/unix/sysv/linux. Tile32 like other 32-bit ports passes
offset in a pair of registers, but doesn't need register alignment,
though  has __ASSUME_ALIGNED_REGISTER_PAIRS enabled. So it should be
handled exceptionally. Here new __ASSUME_READAHEAD_NO_ALIGN option is
introduced in kernel-features.h, and is enabled only for tile.

[1] https://sourceware.org/ml/libc-alpha/2016-09/msg00452.html

v3:
 - option is restored, and exceptional implementation is dropped
   to avoid warning due to multiple inclusion of sysdep.h
v2:
 - remove powerpc and wordsize64 implementations;
 - remove __ASSUME_READAHEAD_ALIGN option;
 - add exception for tile32.
v1: https://sourceware.org/ml/libc-alpha/2016-09/msg00469.html

2016-09-27: Yury Norov  <ynorov@caviumnetworks.com>

	* sysdeps/unix/sysv/linux/arm/readahead.c: Delete.
	* sysdeps/unix/sysv/linux/mips/mips32/readahead.c: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/syscalls.list: Delete
	  readahead generation.
	* sysdeps/unix/sysv/linux/wordsize-64/syscalls.list: Likewise.
	* sysdeps/unix/sysv/linux/readahead.c: Consolidate implementation.
	* sysdeps/unix/sysv/linux/kernel-features.h: New
	  __ASSUME_READAHEAD_NO_ALIGN option.
	* sysdeps/unix/sysv/linux/tile/kernel-features.h: Likewise.

Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
CC: Adhemerval Zanella <adhemerval.zanella@linaro.org>
CC: Florian Weimer <fw@deneb.enyo.de>
---
 sysdeps/unix/sysv/linux/arm/readahead.c            | 37 ----------------------
 sysdeps/unix/sysv/linux/kernel-features.h          |  4 +++
 sysdeps/unix/sysv/linux/mips/mips32/readahead.c    |  1 -
 .../sysv/linux/powerpc/powerpc32/syscalls.list     |  3 --
 sysdeps/unix/sysv/linux/readahead.c                | 13 +++++---
 sysdeps/unix/sysv/linux/tile/kernel-features.h     |  5 +--
 sysdeps/unix/sysv/linux/wordsize-64/syscalls.list  |  1 -
 7 files changed, 15 insertions(+), 49 deletions(-)
 delete mode 100644 sysdeps/unix/sysv/linux/arm/readahead.c
 delete mode 100644 sysdeps/unix/sysv/linux/mips/mips32/readahead.c

diff --git a/sysdeps/unix/sysv/linux/arm/readahead.c b/sysdeps/unix/sysv/linux/arm/readahead.c
deleted file mode 100644
index 9824e6f..0000000
--- a/sysdeps/unix/sysv/linux/arm/readahead.c
+++ /dev/null
@@ -1,37 +0,0 @@
-/* Provide kernel hint to read ahead.
-   Copyright (C) 2002-2016 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library.  If not, see
-   <http://www.gnu.org/licenses/>.  */
-
-#include <errno.h>
-#include <fcntl.h>
-#include <sys/types.h>
-#include <endian.h>
-
-#include <sysdep.h>
-#include <sys/syscall.h>
-
-
-ssize_t
-__readahead (int fd, off64_t offset, size_t count)
-{
-  return INLINE_SYSCALL (readahead, 5, fd, 0,
-			 __LONG_LONG_PAIR ((off_t) (offset >> 32),
-					   (off_t) (offset & 0xffffffff)),
-			 count);
-}
-
-weak_alias (__readahead, readahead)
diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h
index 71ce57a..683c958 100644
--- a/sysdeps/unix/sysv/linux/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/kernel-features.h
@@ -144,6 +144,10 @@
 # define __ASSUME_SENDMMSG	1
 #endif
 
+#ifndef __ASSUME_READAHEAD_NO_ALIGN
+# define __ASSUME_READAHEAD_NO_ALIGN	0
+#endif
+
 /* On most architectures, most socket syscalls are supported for all
    supported kernel versions, but on some socketcall architectures
    separate syscalls were only added later.  */
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/readahead.c b/sysdeps/unix/sysv/linux/mips/mips32/readahead.c
deleted file mode 100644
index 80170c3..0000000
--- a/sysdeps/unix/sysv/linux/mips/mips32/readahead.c
+++ /dev/null
@@ -1 +0,0 @@
-#include <sysdeps/unix/sysv/linux/arm/readahead.c>
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/syscalls.list b/sysdeps/unix/sysv/linux/powerpc/powerpc32/syscalls.list
index 451d508..487bdd0 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/syscalls.list
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/syscalls.list
@@ -7,8 +7,5 @@ lchown		-	lchown		i:sii	__lchown	lchown@@GLIBC_2.0 chown@GLIBC_2.0
 oldgetrlimit	EXTRA	getrlimit	i:ip	__old_getrlimit	getrlimit@GLIBC_2.0
 setrlimit	-	setrlimit	i:ip	__setrlimit	setrlimit@GLIBC_2.0 setrlimit@@GLIBC_2.2
 
-# Due to 64bit alignment there is a dummy second parameter
-readahead	-	readahead	i:iiiii	__readahead	readahead
-
 prlimit64	EXTRA	prlimit64	i:iipp	prlimit64
 fanotify_mark	EXTRA	fanotify_mark	i:iiiiis	fanotify_mark
diff --git a/sysdeps/unix/sysv/linux/readahead.c b/sysdeps/unix/sysv/linux/readahead.c
index 92e5428..cb49906 100644
--- a/sysdeps/unix/sysv/linux/readahead.c
+++ b/sysdeps/unix/sysv/linux/readahead.c
@@ -22,17 +22,20 @@
 
 #include <sysdep.h>
 #include <sys/syscall.h>
-
+#include <kernel-features.h>
 
 #ifdef __NR_readahead
 
+#if __ASSUME_READAHEAD_NO_ALIGN
+# undef __ALIGNMENT_ARG
+# define __ALIGNMENT_ARG
+#endif
+
 ssize_t
 __readahead (int fd, off64_t offset, size_t count)
 {
-  return INLINE_SYSCALL (readahead, 4, fd,
-			 __LONG_LONG_PAIR ((off_t) (offset >> 32),
-					   (off_t) (offset & 0xffffffff)),
-			 count);
+  return INLINE_SYSCALL_CALL (readahead, fd, __ALIGNMENT_ARG
+			      SYSCALL_LL64 (offset), count);
 }
 #else
 ssize_t
diff --git a/sysdeps/unix/sysv/linux/tile/kernel-features.h b/sysdeps/unix/sysv/linux/tile/kernel-features.h
index ded0e43..84d1011 100644
--- a/sysdeps/unix/sysv/linux/tile/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/tile/kernel-features.h
@@ -17,11 +17,12 @@
    <http://www.gnu.org/licenses/>.  */
 
 
-#include_next <kernel-features.h>
-
 /* Define this if your 32-bit syscall API requires 64-bit register
    pairs to start with an even-number register.  */
 #ifndef _LP64
 # define __ASSUME_ALIGNED_REGISTER_PAIRS	1
 # define __ASSUME_FADVISE64_64_NO_ALIGN		1
+# define __ASSUME_READAHEAD_NO_ALIGN		1
 #endif
+
+#include_next <kernel-features.h>
diff --git a/sysdeps/unix/sysv/linux/wordsize-64/syscalls.list b/sysdeps/unix/sysv/linux/wordsize-64/syscalls.list
index 3f3569f..1040e70 100644
--- a/sysdeps/unix/sysv/linux/wordsize-64/syscalls.list
+++ b/sysdeps/unix/sysv/linux/wordsize-64/syscalls.list
@@ -7,7 +7,6 @@ ftruncate	-	ftruncate	i:ii	__ftruncate	ftruncate ftruncate64 __ftruncate64
 truncate	-	truncate	i:si	truncate	truncate64
 getrlimit	-	getrlimit	i:ip	__getrlimit	getrlimit getrlimit64 __getrlimit64
 setrlimit	-	setrlimit	i:ip	__setrlimit	setrlimit setrlimit64
-readahead	-	readahead	i:iii	__readahead	readahead
 sendfile	-	sendfile	i:iipi	sendfile	sendfile64
 sync_file_range	-	sync_file_range	Ci:iiii	sync_file_range
 creat		-	creat		Ci:si	creat		creat64
-- 
2.7.4