um: Update UBD to use pread/pwrite family of functions

This decreases the number of syscalls per read/write by half.

Signed-off-by: Anton Ivanov <aivanov@brocade.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

3 files changed, 26 insertions, 22 deletions

diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
index e8ab93c3e638..39ba20755e03 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c
@@ -535,11 +535,7 @@ static int read_cow_bitmap(int fd, void *buf, int offset, int len)
 {
         int err;
 
-        err = os_seek_file(fd, offset);
-        if (err < 0)
-                return err;
-
-        err = os_read_file(fd, buf, len);
+        err = os_pread_file(fd, buf, len, offset);
         if (err < 0)
                 return err;
 
@@ -1377,14 +1373,8 @@ static int update_bitmap(struct io_thread_req *req)
         if(req->cow_offset == -1)
                 return 0;
 
-        n = os_seek_file(req->fds[1], req->cow_offset);
-        if(n < 0){
-                printk("do_io - bitmap lseek failed : err = %d\n", -n);
-                return 1;
-        }
-
-        n = os_write_file(req->fds[1], &req->bitmap_words,
-                          sizeof(req->bitmap_words));
+        n = os_pwrite_file(req->fds[1], &req->bitmap_words,
+                          sizeof(req->bitmap_words), req->cow_offset);
         if(n != sizeof(req->bitmap_words)){
                 printk("do_io - bitmap update failed, err = %d fd = %d\n", -n,
                        req->fds[1]);
@@ -1399,7 +1389,6 @@ static void do_io(struct io_thread_req *req)
         char *buf;
         unsigned long len;
         int n, nsectors, start, end, bit;
-        int err;
         __u64 off;
 
         if (req->op == UBD_FLUSH) {
@@ -1428,18 +1417,12 @@ static void do_io(struct io_thread_req *req)
                 len = (end - start) * req->sectorsize;
                 buf = &req->buffer[start * req->sectorsize];
 
-                err = os_seek_file(req->fds[bit], off);
-                if(err < 0){
-                        printk("do_io - lseek failed : err = %d\n", -err);
-                        req->error = 1;
-                        return;
-                }
                 if(req->op == UBD_READ){
                         n = 0;
                         do {
                                 buf = &buf[n];
                                 len -= n;
-                                n = os_read_file(req->fds[bit], buf, len);
+                                n = os_pread_file(req->fds[bit], buf, len, off);
                                 if (n < 0) {
                                         printk("do_io - read failed, err = %d "
                                                "fd = %d\n", -n, req->fds[bit]);
@@ -1449,7 +1432,7 @@ static void do_io(struct io_thread_req *req)
                         } while((n < len) && (n != 0));
                         if (n < len) memset(&buf[n], 0, len - n);
                 } else {
-                        n = os_write_file(req->fds[bit], buf, len);
+                        n = os_pwrite_file(req->fds[bit], buf, len, off);
                         if(n != len){
                                 printk("do_io - write failed err = %d "
                                        "fd = %d\n", -n, req->fds[bit]);
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 868e6c3f83dd..7a04ddd85334 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -146,6 +146,8 @@ extern int os_read_file(int fd, void *buf, int len);
 extern int os_write_file(int fd, const void *buf, int count);
 extern int os_sync_file(int fd);
 extern int os_file_size(const char *file, unsigned long long *size_out);
+extern int os_pread_file(int fd, void *buf, int len, unsigned long long offset);
+extern int os_pwrite_file(int fd, const void *buf, int count, unsigned long long offset);
 extern int os_file_modtime(const char *file, unsigned long *modtime);
 extern int os_pipe(int *fd, int stream, int close_on_exec);
 extern int os_set_fd_async(int fd);
diff --git a/arch/um/os-Linux/file.c b/arch/um/os-Linux/file.c
index 26e0164895e4..2db18cbbb0ea 100644
--- a/arch/um/os-Linux/file.c
+++ b/arch/um/os-Linux/file.c
@@ -264,6 +264,15 @@ int os_read_file(int fd, void *buf, int len)
         return n;
 }
 
+int os_pread_file(int fd, void *buf, int len, unsigned long long offset)
+{
+        int n = pread(fd, buf, len, offset);
+
+        if (n < 0)
+                return -errno;
+        return n;
+}
+
 int os_write_file(int fd, const void *buf, int len)
 {
         int n = write(fd, (void *) buf, len);
@@ -282,6 +291,16 @@ int os_sync_file(int fd)
         return n;
 }
 
+int os_pwrite_file(int fd, const void *buf, int len, unsigned long long offset)
+{
+        int n = pwrite(fd, (void *) buf, len, offset);
+
+        if (n < 0)
+                return -errno;
+        return n;
+}
+
+
 int os_file_size(const char *file, unsigned long long *size_out)
 {
         struct uml_stat buf;