[PATCH v2 18/36] fs: add ksys_write() helper; remove in-kernel calls to sys_write()

[Dominik Brodowski]

Using this helper allows us to avoid the in-kernel calls to the sys_write()
syscall.

Cc: Alexander Viro <v...@zeniv.linux.org.uk>
Cc: linux-s...@vger.kernel.org
Signed-off-by: Dominik Brodowski <li...@dominikbrodowski.net>
---
 arch/s390/kernel/compat_linux.c | 2 +-
 fs/read_write.c                 | 9 +++++++--
 include/linux/syscalls.h        | 1 +
 init/do_mounts_rd.c             | 4 ++--
 init/initramfs.c                | 2 +-
 5 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/arch/s390/kernel/compat_linux.c b/arch/s390/kernel/compat_linux.c
index 79b7a3438d54..5a9cfde5fc28 100644
--- a/arch/s390/kernel/compat_linux.c
+++ b/arch/s390/kernel/compat_linux.c
@@ -468,7 +468,7 @@ COMPAT_SYSCALL_DEFINE3(s390_write, unsigned int, fd, const 
char __user *, buf, c
        if ((compat_ssize_t) count < 0)
                return -EINVAL; 
 
-       return sys_write(fd, buf, count);
+       return ksys_write(fd, buf, count);
 }
 
 /*
diff --git a/fs/read_write.c b/fs/read_write.c
index f8547b82dfb3..8e8f0b4f52e2 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -578,8 +578,7 @@ SYSCALL_DEFINE3(read, unsigned int, fd, char __user *, buf, 
size_t, count)
        return ret;
 }
 
-SYSCALL_DEFINE3(write, unsigned int, fd, const char __user *, buf,
-               size_t, count)
+ssize_t ksys_write(unsigned int fd, const char __user *buf, size_t count)
 {
        struct fd f = fdget_pos(fd);
        ssize_t ret = -EBADF;
@@ -595,6 +594,12 @@ SYSCALL_DEFINE3(write, unsigned int, fd, const char __user 
*, buf,
        return ret;
 }
 
+SYSCALL_DEFINE3(write, unsigned int, fd, const char __user *, buf,
+               size_t, count)
+{
+       return ksys_write(fd, buf, count);
+}
+
 SYSCALL_DEFINE4(pread64, unsigned int, fd, char __user *, buf,
                        size_t, count, loff_t, pos)
 {
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 13c7bc43b6ef..c6aa44b6a0a2 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -953,5 +953,6 @@ int ksys_mount(char __user *dev_name, char __user 
*dir_name, char __user *type,
 int ksys_umount(char __user *name, int flags);
 int ksys_dup(unsigned int fildes);
 int ksys_chroot(const char __user *filename);
+ssize_t ksys_write(unsigned int fd, const char __user *buf, size_t count);
 
 #endif
diff --git a/init/do_mounts_rd.c b/init/do_mounts_rd.c
index 99e0b649fc0e..2d365c398ccc 100644
--- a/init/do_mounts_rd.c
+++ b/init/do_mounts_rd.c
@@ -270,7 +270,7 @@ int __init rd_load_image(char *from)
                        printk("Loading disk #%d... ", disk);
                }
                sys_read(in_fd, buf, BLOCK_SIZE);
-               sys_write(out_fd, buf, BLOCK_SIZE);
+               ksys_write(out_fd, buf, BLOCK_SIZE);
 #if !defined(CONFIG_S390)
                if (!(i % 16)) {
                        pr_cont("%c\b", rotator[rotate & 0x3]);
@@ -317,7 +317,7 @@ static long __init compr_fill(void *buf, unsigned long len)
 
 static long __init compr_flush(void *window, unsigned long outcnt)
 {
-       long written = sys_write(crd_outfd, window, outcnt);
+       long written = ksys_write(crd_outfd, window, outcnt);
        if (written != outcnt) {
                if (decompress_error == 0)
                        printk(KERN_ERR
diff --git a/init/initramfs.c b/init/initramfs.c
index 7e99a0038942..6f972df15bf2 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -27,7 +27,7 @@ static ssize_t __init xwrite(int fd, const char *p, size_t 
count)
 
        /* sys_write only can write MAX_RW_COUNT aka 2G-4K bytes at most */
        while (count) {
-               ssize_t rv = sys_write(fd, p, count);
+               ssize_t rv = ksys_write(fd, p, count);
 
                if (rv < 0) {
                        if (rv == -EINTR || rv == -EAGAIN)
-- 
2.16.2