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Message-Id: <1232124344-25892-4-git-send-email-kraxel@redhat.com>
Date: Fri, 16 Jan 2009 17:45:42 +0100
From: Gerd Hoffmann <kraxel@...hat.com>
To: linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
linux-api@...r.kernel.org
Cc: aarcange@...hat.com, Gerd Hoffmann <kraxel@...hat.com>
Subject: [PATCH 3/5] Add preadv and pwritev system calls.
This patch adds preadv and pwritev system calls. These syscalls are a
pretty straightforward combination of pread and readv (same for write).
They are quite useful for doing vectored I/O in threaded applications.
Using lseek+readv instead opens race windows you'll have to plug with
locking.
Other systems have such system calls too, for example NetBSD, check
here: http://www.daemon-systems.org/man/preadv.2.html
The application-visible interface provided by glibc should look like
this to be compatible to the existing implementations in the *BSD family:
ssize_t preadv(int d, const struct iovec *iov, int iovcnt, off_t offset);
ssize_t pwritev(int d, const struct iovec *iov, int iovcnt, off_t offset);
This prototype has one problem though: On 32bit archs is the (64bit)
offset argument unaligned, which the syscall ABI of several archs
doesn't allow to do. At least s390 needs a wrapper in glibc to handle
this. As we'll need a wrappers in glibc anyway I've decided to push
problem to glibc entriely and use a syscall prototype which works
without arch-specific wrappers inside the kernel: The offset argument
is explicitly splitted into two 32bit values.
The patch sports the actual system call implementation and the windup in
the x86 system call tables. Other archs follow as separate patches.
Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
---
arch/x86/ia32/ia32entry.S | 2 +
arch/x86/include/asm/unistd_32.h | 2 +
arch/x86/include/asm/unistd_64.h | 4 +++
arch/x86/kernel/syscall_table_32.S | 2 +
fs/compat.c | 36 ++++++++++++++++++++++++++
fs/read_write.c | 50 ++++++++++++++++++++++++++++++++++++
include/linux/compat.h | 6 ++++
include/linux/syscalls.h | 4 +++
8 files changed, 106 insertions(+), 0 deletions(-)
diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 256b00b..9a8501b 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -826,4 +826,6 @@ ia32_sys_call_table:
.quad sys_dup3 /* 330 */
.quad sys_pipe2
.quad sys_inotify_init1
+ .quad compat_sys_preadv
+ .quad compat_sys_pwritev
ia32_syscall_end:
diff --git a/arch/x86/include/asm/unistd_32.h b/arch/x86/include/asm/unistd_32.h
index f2bba78..6e72d74 100644
--- a/arch/x86/include/asm/unistd_32.h
+++ b/arch/x86/include/asm/unistd_32.h
@@ -338,6 +338,8 @@
#define __NR_dup3 330
#define __NR_pipe2 331
#define __NR_inotify_init1 332
+#define __NR_preadv 333
+#define __NR_pwritev 334
#ifdef __KERNEL__
diff --git a/arch/x86/include/asm/unistd_64.h b/arch/x86/include/asm/unistd_64.h
index d2e415e..f818294 100644
--- a/arch/x86/include/asm/unistd_64.h
+++ b/arch/x86/include/asm/unistd_64.h
@@ -653,6 +653,10 @@ __SYSCALL(__NR_dup3, sys_dup3)
__SYSCALL(__NR_pipe2, sys_pipe2)
#define __NR_inotify_init1 294
__SYSCALL(__NR_inotify_init1, sys_inotify_init1)
+#define __NR_preadv 295
+__SYSCALL(__NR_preadv, sys_preadv)
+#define __NR_pwritev 296
+__SYSCALL(__NR_pwritev, sys_pwritev)
#ifndef __NO_STUBS
diff --git a/arch/x86/kernel/syscall_table_32.S b/arch/x86/kernel/syscall_table_32.S
index e2e86a0..106204c 100644
--- a/arch/x86/kernel/syscall_table_32.S
+++ b/arch/x86/kernel/syscall_table_32.S
@@ -332,3 +332,5 @@ ENTRY(sys_call_table)
.long sys_dup3 /* 330 */
.long sys_pipe2
.long sys_inotify_init1
+ .long sys_preadv
+ .long sys_pwritev
diff --git a/fs/compat.c b/fs/compat.c
index 9f20d10..20fec0e 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -1202,6 +1202,24 @@ compat_sys_readv(unsigned long fd, const struct compat_iovec __user *vec, unsign
return ret;
}
+asmlinkage ssize_t
+compat_sys_preadv(unsigned long fd, const struct compat_iovec __user *vec,
+ unsigned long vlen, u32 pos_high, u32 pos_low)
+{
+ loff_t pos = ((loff_t)pos_high << 32) | pos_low;
+ struct file *file;
+ ssize_t ret;
+
+ if (pos < 0)
+ return -EINVAL;
+ file = fget(fd);
+ if (!file)
+ return -EBADF;
+ ret = compat_readv(file, vec, vlen, &pos);
+ fput(file);
+ return ret;
+}
+
static size_t compat_writev(struct file *file, const struct compat_iovec __user *vec,
unsigned long vlen, loff_t *pos)
{
@@ -1237,6 +1255,24 @@ compat_sys_writev(unsigned long fd, const struct compat_iovec __user *vec, unsig
return ret;
}
+asmlinkage ssize_t
+compat_sys_pwritev(unsigned long fd, const struct compat_iovec __user *vec,
+ unsigned long vlen, u32 pos_high, u32 pos_low)
+{
+ loff_t pos = ((loff_t)pos_high << 32) | pos_low;
+ struct file *file;
+ ssize_t ret;
+
+ if (pos < 0)
+ return -EINVAL;
+ file = fget(fd);
+ if (!file)
+ return -EBADF;
+ ret = compat_writev(file, vec, vlen, &pos);
+ fput(file);
+ return ret;
+}
+
asmlinkage long
compat_sys_vmsplice(int fd, const struct compat_iovec __user *iov32,
unsigned int nr_segs, unsigned int flags)
diff --git a/fs/read_write.c b/fs/read_write.c
index 400fe81..39de95c 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -731,6 +731,56 @@ SYSCALL_DEFINE3(writev, unsigned long, fd, const struct iovec __user *, vec,
return ret;
}
+SYSCALL_DEFINE5(preadv, unsigned long, fd, const struct iovec __user *, vec,
+ unsigned long, vlen, u32, pos_high, u32, pos_low)
+{
+ loff_t pos = ((loff_t)pos_high << 32) | pos_low;
+ struct file *file;
+ ssize_t ret = -EBADF;
+ int fput_needed;
+
+ if (pos < 0)
+ return -EINVAL;
+
+ file = fget_light(fd, &fput_needed);
+ if (file) {
+ ret = -ESPIPE;
+ if (file->f_mode & FMODE_PREAD)
+ ret = vfs_readv(file, vec, vlen, &pos);
+ fput_light(file, fput_needed);
+ }
+
+ if (ret > 0)
+ add_rchar(current, ret);
+ inc_syscr(current);
+ return ret;
+}
+
+SYSCALL_DEFINE5(pwritev, unsigned long, fd, const struct iovec __user *, vec,
+ unsigned long, vlen, u32, pos_high, u32, pos_low)
+{
+ loff_t pos = ((loff_t)pos_high << 32) | pos_low;
+ struct file *file;
+ ssize_t ret = -EBADF;
+ int fput_needed;
+
+ if (pos < 0)
+ return -EINVAL;
+
+ file = fget_light(fd, &fput_needed);
+ if (file) {
+ ret = -ESPIPE;
+ if (file->f_mode & FMODE_PWRITE)
+ ret = vfs_writev(file, vec, vlen, &pos);
+ fput_light(file, fput_needed);
+ }
+
+ if (ret > 0)
+ add_wchar(current, ret);
+ inc_syscw(current);
+ return ret;
+}
+
static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
size_t count, loff_t max)
{
diff --git a/include/linux/compat.h b/include/linux/compat.h
index 3fd2194..79dba49 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -183,6 +183,12 @@ asmlinkage ssize_t compat_sys_readv(unsigned long fd,
const struct compat_iovec __user *vec, unsigned long vlen);
asmlinkage ssize_t compat_sys_writev(unsigned long fd,
const struct compat_iovec __user *vec, unsigned long vlen);
+asmlinkage ssize_t compat_sys_preadv(unsigned long fd,
+ const struct compat_iovec __user *vec,
+ unsigned long vlen, u32 pos_high, u32 pos_low);
+asmlinkage ssize_t compat_sys_pwritev(unsigned long fd,
+ const struct compat_iovec __user *vec,
+ unsigned long vlen, u32 pos_high, u32 pos_low);
int compat_do_execve(char * filename, compat_uptr_t __user *argv,
compat_uptr_t __user *envp, struct pt_regs * regs);
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 16875f8..333377e 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -456,6 +456,10 @@ asmlinkage long sys_pread64(unsigned int fd, char __user *buf,
size_t count, loff_t pos);
asmlinkage long sys_pwrite64(unsigned int fd, const char __user *buf,
size_t count, loff_t pos);
+asmlinkage long sys_preadv(unsigned long fd, const struct iovec __user *vec,
+ unsigned long vlen, u32 pos_high, u32 pos_low);
+asmlinkage long sys_pwritev(unsigned long fd, const struct iovec __user *vec,
+ unsigned long vlen, u32 pos_high, u32 pos_low);
asmlinkage long sys_getcwd(char __user *buf, unsigned long size);
asmlinkage long sys_mkdir(const char __user *pathname, int mode);
asmlinkage long sys_chdir(const char __user *filename);
--
1.6.1
--
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