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[PATCH 2/5][TAKE2] fallocate() on s390

To: torvalds@xxxxxxxx, akpm@xxxxxxxxxxxxxxxxxxxx
Subject: [PATCH 2/5][TAKE2] fallocate() on s390
From: "Amit K. Arora" <aarora@xxxxxxxxxxxxxxxxxx>
Date: Mon, 14 May 2007 20:18:34 +0530
Cc: linux-fsdevel@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, suparna@xxxxxxxxxx, cmm@xxxxxxxxxx
In-reply-to: <20070514142820.GA31468@amitarora.in.ibm.com>
References: <20070329101010.7a2b8783.akpm@linux-foundation.org> <20070330071417.GI355@devserv.devel.redhat.com> <20070417125514.GA7574@amitarora.in.ibm.com> <20070418130600.GW5967@schatzie.adilger.int> <20070420135146.GA21352@amitarora.in.ibm.com> <20070420145918.GY355@devserv.devel.redhat.com> <20070424121632.GA10136@amitarora.in.ibm.com> <20070426175056.GA25321@amitarora.in.ibm.com> <20070514132926.GA30768@amitarora.in.ibm.com> <20070514142820.GA31468@amitarora.in.ibm.com>
Sender: xfs-bounce@xxxxxxxxxxx
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This is the patch suggested by Martin Schwidefsky. Here are the comments
and patch from him.

-------------
From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>

This patch implements support of fallocate system call on s390(x)
platform. A wrapper is added to address the issue which s390 ABI has
with the arguments of this system call.

Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
---

 arch/s390/kernel/compat_wrapper.S |   10 ++++++++++
 arch/s390/kernel/sys_s390.c       |   29 +++++++++++++++++++++++++++++
 arch/s390/kernel/syscalls.S       |    1 +
 include/asm-s390/unistd.h         |    3 ++-
 4 files changed, 42 insertions(+), 1 deletion(-)

Index: linux-2.6.21/arch/s390/kernel/compat_wrapper.S
===================================================================
--- linux-2.6.21.orig/arch/s390/kernel/compat_wrapper.S
+++ linux-2.6.21/arch/s390/kernel/compat_wrapper.S
@@ -1682,3 +1682,13 @@ compat_sys_utimes_wrapper:
        llgtr   %r2,%r2                 # char *
        llgtr   %r3,%r3                 # struct compat_timeval *
        jg      compat_sys_utimes
+
+       .globl  sys_fallocate_wrapper
+sys_fallocate_wrapper:
+       lgfr    %r2,%r2                 # int
+       lgfr    %r3,%r3                 # int
+       sllg    %r4,%r4,32              # get high word of 64bit loff_t
+       lr      %r4,%r5                 # get low word of 64bit loff_t
+       sllg    %r5,%r6,32              # get high word of 64bit loff_t
+       l       %r5,164(%r15)           # get low word of 64bit loff_t
+       jg      sys_fallocate
Index: linux-2.6.21/arch/s390/kernel/syscalls.S
===================================================================
--- linux-2.6.21.orig/arch/s390/kernel/syscalls.S
+++ linux-2.6.21/arch/s390/kernel/syscalls.S
@@ -322,3 +322,4 @@ NI_SYSCALL                                                  
/* 310 sys_move_pages *
 SYSCALL(sys_getcpu,sys_getcpu,sys_getcpu_wrapper)
 SYSCALL(sys_epoll_pwait,sys_epoll_pwait,compat_sys_epoll_pwait_wrapper)
 SYSCALL(sys_utimes,sys_utimes,compat_sys_utimes_wrapper)
+SYSCALL(s390_fallocate,sys_fallocate,sys_fallocate_wrapper)
Index: linux-2.6.21/arch/s390/kernel/sys_s390.c
===================================================================
--- linux-2.6.21.orig/arch/s390/kernel/sys_s390.c
+++ linux-2.6.21/arch/s390/kernel/sys_s390.c
@@ -286,3 +286,32 @@ int kernel_execve(const char *filename, 
                  "d" (__arg3) : "memory");
        return __svcres;
 }
+
+#ifndef CONFIG_64BIT
+/*
+ * This is a wrapper to call sys_fallocate(). For 31 bit s390 the last
+ * 64 bit argument "len" is split into the upper and lower 32 bits. The
+ * system call wrapper in the user space loads the value to %r6/%r7.
+ * The code in entry.S keeps the values in %r2 - %r6 where they are and
+ * stores %r7 to 96(%r15). But the standard C linkage requires that
+ * the whole 64 bit value for len is stored on the stack and doesn't
+ * use %r6 at all. So s390_fallocate has to convert the arguments from
+ *   %r2: fd, %r3: mode, %r4/%r5: offset, %r6/96(%r15)-99(%r15): len
+ * to
+ *   %r2: fd, %r3: mode, %r4/%r5: offset, 96(%r15)-103(%r15): len
+ */
+asmlinkage long s390_fallocate(int fd, int mode, loff_t offset,
+                              u32 len_high, u32 len_low)
+{
+       union {
+               u64 len;
+               struct {
+                       u32 high;
+                       u32 low;
+               };
+       } cv;
+       cv.high = len_high;
+       cv.low = len_low;
+       return sys_fallocate(fd, mode, offset, cv.len);
+}
+#endif
Index: linux-2.6.21/include/asm-s390/unistd.h
===================================================================
--- linux-2.6.21.orig/include/asm-s390/unistd.h
+++ linux-2.6.21/include/asm-s390/unistd.h
@@ -251,8 +251,9 @@
 #define __NR_getcpu            311
 #define __NR_epoll_pwait       312
 #define __NR_utimes            313
+#define __NR_fallocate         314
 
-#define NR_syscalls 314
+#define NR_syscalls 315
 
 /* 
  * There are some system calls that are not present on 64 bit, some


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