Re: [PATCH] POSIX_FADV_{DONTNEED,NOREUSE} defines on s390-64.

[Martin Schwidefsky <schwidefsky at de dot ibm dot com>]

> > Changing glibc might be the simpler solution but it the least friendly
> > to users.  Can you reconsider it?
> 
> I'll try to come up with a kernel patch. But it won't be a nice patch.
> I have the feeling that the kernel guys won't like it either ..

Hmm, the patch doesn't look as bad as expected. Still can't say that
I like the solution. I'll ask the kernel guys what they think about it.

blue skies,
  Martin.


diffstat:
 arch/s390/kernel/compat_linux.c   |   38 ++++++++++++++++++++++++++++++++++++++
 arch/s390/kernel/compat_wrapper.S |    4 ++--
 include/linux/fadvise.h           |   10 ++++++++++
 3 files changed, 50 insertions(+), 2 deletions(-)

diff -urpN linux-2.6/arch/s390/kernel/compat_linux.c linux-2.6-patched/arch/s390/kernel/compat_linux.c
--- linux-2.6/arch/s390/kernel/compat_linux.c	2005-06-17 21:48:29.000000000 +0200
+++ linux-2.6-patched/arch/s390/kernel/compat_linux.c	2005-07-12 13:28:31.000000000 +0200
@@ -58,6 +58,7 @@
 #include <linux/compat.h>
 #include <linux/vfs.h>
 #include <linux/ptrace.h>
+#include <linux/fadvise.h>
 
 #include <asm/types.h>
 #include <asm/ipc.h>
@@ -1043,3 +1044,40 @@ sys32_timer_create(clockid_t which_clock
 
 	return ret;
 }
+
+/*
+ * 31 bit emulation wrapper functions for sys_fadvise64/fadvise64_64.
+ * These need to rewrite the advise values for POSIX_FADV_{DONTNEED,NOREUSE}
+ * because the 31 bit values differ from the 64 bit values.
+ */
+
+asmlinkage long
+sys32_fadvise64(int fd, loff_t offset, size_t len, int advise)
+{
+	if (advise == 4)
+		advise = POSIX_FADV_DONTNEED;
+	else if (advise == 5)
+		advise = POSIX_FADV_NOREUSE;
+	return sys_fadvise64(fd, offset, len, advise);
+}
+
+struct fadvise64_64_args {
+	int fd;
+	long long offset;
+	long long len;
+	int advice;
+};
+
+asmlinkage long
+sys32_fadvise64_64(struct fadvise64_64_args __user *args)
+{
+	struct fadvise64_64_args a;
+
+	if ( copy_from_user(&a, args, sizeof(a)) )
+		return -EFAULT;
+	if (a.advice == 4)
+		a.advice = POSIX_FADV_DONTNEED;
+	else if (a.advice == 5)
+		a.advice = POSIX_FADV_NOREUSE;
+	return sys_fadvise64_64(a.fd, a.offset, a.len, a.advice);
+}
diff -urpN linux-2.6/arch/s390/kernel/compat_wrapper.S linux-2.6-patched/arch/s390/kernel/compat_wrapper.S
--- linux-2.6/arch/s390/kernel/compat_wrapper.S	2005-07-12 13:27:13.000000000 +0200
+++ linux-2.6-patched/arch/s390/kernel/compat_wrapper.S	2005-07-12 13:28:36.000000000 +0200
@@ -1251,12 +1251,12 @@ sys32_fadvise64_wrapper:
 	or	%r3,%r4			# get low word of 64bit loff_t
 	llgfr	%r4,%r5			# size_t (unsigned long)
 	lgfr	%r5,%r6			# int
-	jg	sys_fadvise64
+	jg	sys32_fadvise64
 
 	.globl	sys32_fadvise64_64_wrapper
 sys32_fadvise64_64_wrapper:
 	llgtr	%r2,%r2			# struct fadvise64_64_args *
-	jg	s390_fadvise64_64
+	jg	sys32_fadvise64_64
 
 	.globl	sys32_clock_settime_wrapper
 sys32_clock_settime_wrapper:
diff -urpN linux-2.6/include/linux/fadvise.h linux-2.6-patched/include/linux/fadvise.h
--- linux-2.6/include/linux/fadvise.h	2005-06-17 21:48:29.000000000 +0200
+++ linux-2.6-patched/include/linux/fadvise.h	2005-07-12 13:28:40.000000000 +0200
@@ -5,7 +5,17 @@
 #define POSIX_FADV_RANDOM	1 /* Expect random page references.  */
 #define POSIX_FADV_SEQUENTIAL	2 /* Expect sequential page references.  */
 #define POSIX_FADV_WILLNEED	3 /* Will need these pages.  */
+
+/*
+ * The advise values for POSIX_FADV_DONTNEED and POSIX_ADV_NOREUSE
+ * for s390-64 differ from the values for the rest of the world.
+ */
+#if defined(__s390x__)
+#define POSIX_FADV_DONTNEED	6 /* Don't need these pages.  */
+#define POSIX_FADV_NOREUSE	7 /* Data will be accessed once.  */
+#else
 #define POSIX_FADV_DONTNEED	4 /* Don't need these pages.  */
 #define POSIX_FADV_NOREUSE	5 /* Data will be accessed once.  */
+#endif
 
 #endif	/* FADVISE_H_INCLUDED */