[PATCH v2 22/41] savevm/QEMUFile: introduce qemu_fopen_fd

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

Introduce nonblocking fd read backend of QEMUFile.
This will be used by postcopy live migration.

Signed-off-by: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>
---
 qemu-file.h |    1 +
 savevm.c    |   40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 0 deletions(-)

diff --git a/qemu-file.h b/qemu-file.h
index 1a12e7d..af5b123 100644
--- a/qemu-file.h
+++ b/qemu-file.h
@@ -68,6 +68,7 @@ QEMUFile *qemu_fopen_ops(void *opaque, QEMUFilePutBufferFunc *put_buffer,
 QEMUFile *qemu_fopen(const char *filename, const char *mode);
 QEMUFile *qemu_fdopen(int fd, const char *mode);
 QEMUFile *qemu_fopen_socket(int fd);
+QEMUFile *qemu_fopen_fd(int fd);
 QEMUFile *qemu_popen(FILE *popen_file, const char *mode);
 QEMUFile *qemu_popen_cmd(const char *command, const char *mode);
 int qemu_file_fd(QEMUFile *f);
diff --git a/savevm.c b/savevm.c
index 2fb0c3e..5640614 100644
--- a/savevm.c
+++ b/savevm.c
@@ -207,6 +207,35 @@ static int socket_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)
     return len;
 }
 
+static int fd_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)
+{
+    QEMUFileFD *s = opaque;
+    ssize_t len = 0;
+
+    while (size > 0) {
+        ssize_t ret = read(s->file->fd, buf, size);
+        if (ret == -1) {
+            if (errno == EINTR) {
+                continue;
+            }
+            if (len == 0) {
+                len = -errno;
+            }
+            break;
+        }
+
+        if (ret == 0) {
+            /* the write end of the pipe is closed */
+            break;
+        }
+        len += ret;
+        buf += ret;
+        size -= ret;
+    }
+
+    return len;
+}
+
 static int fd_close(void *opaque)
 {
     QEMUFileFD *s = opaque;
@@ -333,6 +362,17 @@ QEMUFile *qemu_fopen_socket(int fd)
     return s->file;
 }
 
+QEMUFile *qemu_fopen_fd(int fd)
+{
+    QEMUFileFD *s = g_malloc0(sizeof(*s));
+
+    fcntl_setfl(fd, O_NONBLOCK);
+    s->file = qemu_fopen_ops(s, NULL, fd_get_buffer, fd_close,
+                             NULL, NULL, NULL);
+    s->file->fd = fd;
+    return s->file;
+}
+
 static int file_put_buffer(void *opaque, const uint8_t *buf,
                             int64_t pos, int size)
 {
-- 
1.7.1.1

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