[PATCH] Consolidate Linux readahead() implementations

[Yury Norov <ynorov@caviumnetworks.com>]

All Linux users pass 4 arguments to readahead() except arm and mips.
That two also pass an alignement. Usually to have single implementation,
__ASSUME_ALIGNED_REGISTER_PAIRS option is used. But readahead() cannot
do this because __ASSUME_ALIGNED_REGISTER_PAIRS is also enabled for tile
and powerpc.

To consolidate all implementations, new option  __ASSUME_READAHEAD_ALIGN
is introduced here, and enabled only for arm and mips. This is also the
case for new arm64/ilp32 as it's the arm32 successor.

2016-09-22: Yury Norov  <ynorov@caviumnetworks.com>
	* sysdeps/unix/sysv/linux/arm/kernel-features.h: new
	  __ASSUME_READAHEAD_ALIGN option.
	* sysdeps/unix/sysv/linux/mips/kernel-features.h: Likewise.
	* sysdeps/unix/sysv/linux/kernel-features.h: Likewise.
	* sysdeps/unix/sysv/linux/arm/readahead.c: Remove.
	* sysdeps/unix/sysv/linux/mips/mips32/readahead.c: Remove.
	* sysdeps/unix/sysv/linux/readahead.c: insert padding
	  register if __ASSUME_READAHEAD_ALIGN is enabled.

Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
CC: Adhemerval Zanella <adhemerval.zanella@linaro.org>
---
 sysdeps/unix/sysv/linux/arm/kernel-features.h   |  2 ++
 sysdeps/unix/sysv/linux/arm/readahead.c         | 37 -------------------------
 sysdeps/unix/sysv/linux/kernel-features.h       |  5 ++++
 sysdeps/unix/sysv/linux/mips/kernel-features.h  |  1 +
 sysdeps/unix/sysv/linux/mips/mips32/readahead.c |  1 -
 sysdeps/unix/sysv/linux/readahead.c             | 11 +++++++-
 6 files changed, 18 insertions(+), 39 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/kernel-features.h b/sysdeps/unix/sysv/linux/arm/kernel-features.h
index 628d27f..cb3b6aa 100644
--- a/sysdeps/unix/sysv/linux/arm/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/arm/kernel-features.h
@@ -17,6 +17,8 @@
    License along with the GNU C Library.  If not, see
    <http://www.gnu.org/licenses/>.  */
 
+#define __ASSUME_READAHEAD_ALIGN	1
+
 #include_next <kernel-features.h>
 
 /* The ARM kernel before 3.14.3 may or may not support
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..24216e5 100644
--- a/sysdeps/unix/sysv/linux/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/kernel-features.h
@@ -50,6 +50,11 @@
 #define __ASSUME_ST_INO_64_BIT		1
 #endif
 
+#ifndef __ASSUME_READAHEAD_ALIGN
+/* readahead() adds padding to registers if this control is enabled.  */
+# define __ASSUME_READAHEAD_ALIGN	0
+#endif
+
 /* The statfs64 syscalls are available in 2.5.74 (but not for alpha).  */
 #define __ASSUME_STATFS64	1
 
diff --git a/sysdeps/unix/sysv/linux/mips/kernel-features.h b/sysdeps/unix/sysv/linux/mips/kernel-features.h
index b486d90..88f4f5e 100644
--- a/sysdeps/unix/sysv/linux/mips/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/mips/kernel-features.h
@@ -31,6 +31,7 @@
 /* Define this if your 32-bit syscall API requires 64-bit register
    pairs to start with an even-number register.  */
 #if _MIPS_SIM == _ABIO32
+# define __ASSUME_READAHEAD_ALIGN		1
 # define __ASSUME_ALIGNED_REGISTER_PAIRS	1
 #endif
 
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/readahead.c b/sysdeps/unix/sysv/linux/readahead.c
index 92e5428..d31bd6e 100644
--- a/sysdeps/unix/sysv/linux/readahead.c
+++ b/sysdeps/unix/sysv/linux/readahead.c
@@ -23,13 +23,22 @@
 #include <sysdep.h>
 #include <sys/syscall.h>
 
+#include <kernel-features.h>
 
 #ifdef __NR_readahead
 
+#if __ASSUME_READAHEAD_ALIGN
+# define __READAHEAD_ARGS		5
+# define __READAHEAD_ALIGN		0,
+#else
+# define __READAHEAD_ARGS		4
+# define __READAHEAD_ALIGN
+#endif
+
 ssize_t
 __readahead (int fd, off64_t offset, size_t count)
 {
-  return INLINE_SYSCALL (readahead, 4, fd,
+  return INLINE_SYSCALL (readahead, __READAHEAD_ARGS, fd, __READAHEAD_ALIGN
 			 __LONG_LONG_PAIR ((off_t) (offset >> 32),
 					   (off_t) (offset & 0xffffffff)),
 			 count);
-- 
2.7.4