Fix some issues with QEMUFile

This patch allows QEMUFile's read and write operations to return 
negative error codes.  This is necessary to detect things like closed 
streams during live migration.

It also removes unused code for QEMUFileFD write path.  Finally, it 
makes sure to avoid attempting to flush an output buffer if the file
is only being used for input.  This was spotted by Uri Lublin.
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5474 c046a42c-6fe2-441c-8c8c-71466251a162

hw/hw.h

@@ -11,8 +11,8 @@
  * The pos argument can be ignored if the file is only being used for
  * streaming.  The handler should try to write all of the data it can.
  */
-typedef void (QEMUFilePutBufferFunc)(void *opaque, const uint8_t *buf,
-                                     int64_t pos, int size);
+typedef int (QEMUFilePutBufferFunc)(void *opaque, const uint8_t *buf,
+                                    int64_t pos, int size);
 
 /* Read a chunk of data from a file at the given position.  The pos argument
  * can be ignored if the file is only be used for streaming.  The number of
@@ -64,6 +64,7 @@ unsigned int qemu_get_be16(QEMUFile *f);
 unsigned int qemu_get_be32(QEMUFile *f);
 uint64_t qemu_get_be64(QEMUFile *f);
 int qemu_file_rate_limit(QEMUFile *f);
+int qemu_file_has_error(QEMUFile *f);
 
 /* Try to send any outstanding data.  This function is useful when output is
  * halted due to rate limiting or EAGAIN errors occur as it can be used to

vl.c

@@ -6197,12 +6197,15 @@ struct QEMUFile {
     QEMUFileCloseFunc *close;
     QEMUFileRateLimit *rate_limit;
     void *opaque;
+    int is_write;
 
     int64_t buf_offset; /* start of buffer when writing, end of buffer
                            when reading */
     int buf_index;
     int buf_size; /* 0 when writing */
     uint8_t buf[IO_BUF_SIZE];
+
+    int has_error;
 };
 
 typedef struct QEMUFileFD
@@ -6211,34 +6214,6 @@ typedef struct QEMUFileFD
     QEMUFile *file;
 } QEMUFileFD;
 
-static void fd_put_notify(void *opaque)
-{
-    QEMUFileFD *s = opaque;
-
-    /* Remove writable callback and do a put notify */
-    qemu_set_fd_handler2(s->fd, NULL, NULL, NULL, NULL);
-    qemu_file_put_notify(s->file);
-}
-
-static void fd_put_buffer(void *opaque, const uint8_t *buf,
-                          int64_t pos, int size)
-{
-    QEMUFileFD *s = opaque;
-    ssize_t len;
-
-    do {
-        len = write(s->fd, buf, size);
-    } while (len == -1 && errno == EINTR);
-
-    if (len == -1)
-        len = -errno;
-
-    /* When the fd becomes writable again, register a callback to do
-     * a put notify */
-    if (len == -EAGAIN)
-        qemu_set_fd_handler2(s->fd, NULL, NULL, fd_put_notify, s);
-}
-
 static int fd_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)
 {
     QEMUFileFD *s = opaque;
@@ -6269,7 +6244,7 @@ QEMUFile *qemu_fopen_fd(int fd)
         return NULL;
 
     s->fd = fd;
-    s->file = qemu_fopen_ops(s, fd_put_buffer, fd_get_buffer, fd_close, NULL);
+    s->file = qemu_fopen_ops(s, NULL, fd_get_buffer, fd_close, NULL);
     return s->file;
 }
 
@@ -6278,12 +6253,13 @@ typedef struct QEMUFileStdio
     FILE *outfile;
 } QEMUFileStdio;
 
-static void file_put_buffer(void *opaque, const uint8_t *buf,
+static int file_put_buffer(void *opaque, const uint8_t *buf,
                             int64_t pos, int size)
 {
     QEMUFileStdio *s = opaque;
     fseek(s->outfile, pos, SEEK_SET);
     fwrite(buf, 1, size, s->outfile);
+    return size;
 }
 
 static int file_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)
@@ -6331,11 +6307,12 @@ typedef struct QEMUFileBdrv
     int64_t base_offset;
 } QEMUFileBdrv;
 
-static void bdrv_put_buffer(void *opaque, const uint8_t *buf,
-                            int64_t pos, int size)
+static int bdrv_put_buffer(void *opaque, const uint8_t *buf,
+                           int64_t pos, int size)
 {
     QEMUFileBdrv *s = opaque;
     bdrv_pwrite(s->bs, s->base_offset + pos, buf, size);
+    return size;
 }
 
 static int bdrv_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)
@@ -6384,18 +6361,29 @@ QEMUFile *qemu_fopen_ops(void *opaque, QEMUFilePutBufferFunc *put_buffer,
     f->get_buffer = get_buffer;
     f->close = close;
     f->rate_limit = rate_limit;
+    f->is_write = 0;
 
     return f;
 }
 
+int qemu_file_has_error(QEMUFile *f)
+{
+    return f->has_error;
+}
+
 void qemu_fflush(QEMUFile *f)
 {
     if (!f->put_buffer)
         return;
 
-    if (f->buf_index > 0) {
-        f->put_buffer(f->opaque, f->buf, f->buf_offset, f->buf_index);
-        f->buf_offset += f->buf_index;
+    if (f->is_write && f->buf_index > 0) {
+        int len;
+
+        len = f->put_buffer(f->opaque, f->buf, f->buf_offset, f->buf_index);
+        if (len > 0)
+            f->buf_offset += f->buf_index;
+        else
+            f->has_error = 1;
         f->buf_index = 0;
     }
 }
@@ -6407,13 +6395,16 @@ static void qemu_fill_buffer(QEMUFile *f)
     if (!f->get_buffer)
         return;
 
-    len = f->get_buffer(f->opaque, f->buf, f->buf_offset, IO_BUF_SIZE);
-    if (len < 0)
-        len = 0;
+    if (f->is_write)
+        abort();
 
-    f->buf_index = 0;
-    f->buf_size = len;
-    f->buf_offset += len;
+    len = f->get_buffer(f->opaque, f->buf, f->buf_offset, IO_BUF_SIZE);
+    if (len > 0) {
+        f->buf_index = 0;
+        f->buf_size = len;
+        f->buf_offset += len;
+    } else if (len != -EAGAIN)
+        f->has_error = 1;
 }
 
 int qemu_fclose(QEMUFile *f)
@@ -6434,11 +6425,19 @@ void qemu_file_put_notify(QEMUFile *f)
 void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size)
 {
     int l;
-    while (size > 0) {
+
+    if (!f->has_error && f->is_write == 0 && f->buf_index > 0) {
+        fprintf(stderr,
+                "Attempted to write to buffer while read buffer is not empty\n");
+        abort();
+    }
+
+    while (!f->has_error && size > 0) {
         l = IO_BUF_SIZE - f->buf_index;
         if (l > size)
             l = size;
         memcpy(f->buf + f->buf_index, buf, l);
+        f->is_write = 1;
         f->buf_index += l;
         buf += l;
         size -= l;
@@ -6449,7 +6448,14 @@ void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size)
 
 void qemu_put_byte(QEMUFile *f, int v)
 {
+    if (!f->has_error && f->is_write == 0 && f->buf_index > 0) {
+        fprintf(stderr,
+                "Attempted to write to buffer while read buffer is not empty\n");
+        abort();
+    }
+
     f->buf[f->buf_index++] = v;
+    f->is_write = 1;
     if (f->buf_index >= IO_BUF_SIZE)
         qemu_fflush(f);
 }
@@ -6458,6 +6464,9 @@ int qemu_get_buffer(QEMUFile *f, uint8_t *buf, int size1)
 {
     int size, l;
 
+    if (f->is_write)
+        abort();
+
     size = size1;
     while (size > 0) {
         l = f->buf_size - f->buf_index;
@@ -6479,6 +6488,9 @@ int qemu_get_buffer(QEMUFile *f, uint8_t *buf, int size1)
 
 int qemu_get_byte(QEMUFile *f)
 {
+    if (f->is_write)
+        abort();
+
     if (f->buf_index >= f->buf_size) {
         qemu_fill_buffer(f);
         if (f->buf_index >= f->buf_size)
@@ -6671,6 +6683,9 @@ int qemu_savevm_state_begin(QEMUFile *f)
         se->save_live_state(f, QEMU_VM_SECTION_START, se->opaque);
     }
 
+    if (qemu_file_has_error(f))
+        return -EIO;
+
     return 0;
 }
 
@@ -6693,6 +6708,9 @@ int qemu_savevm_state_iterate(QEMUFile *f)
     if (ret)
         return 1;
 
+    if (qemu_file_has_error(f))
+        return -EIO;
+
     return 0;
 }
 
@@ -6734,6 +6752,9 @@ int qemu_savevm_state_complete(QEMUFile *f)
 
     qemu_put_byte(f, QEMU_VM_EOF);
 
+    if (qemu_file_has_error(f))
+        return -EIO;
+
     return 0;
 }
 
@@ -6758,8 +6779,12 @@ int qemu_savevm_state(QEMUFile *f)
     ret = qemu_savevm_state_complete(f);
 
 out:
-    if (saved_vm_running)
+    if (qemu_file_has_error(f))
+        ret = -EIO;
+
+    if (!ret && saved_vm_running)
         vm_start();
+
     return ret;
 }
 
@@ -6815,6 +6840,10 @@ static int qemu_loadvm_state_v2(QEMUFile *f)
         /* always seek to exact end of record */
         qemu_fseek(f, cur_pos + record_len, SEEK_SET);
     }
+
+    if (qemu_file_has_error(f))
+        return -EIO;
+
     return 0;
 }
 
@@ -6913,6 +6942,9 @@ out:
         qemu_free(le);
     }
 
+    if (qemu_file_has_error(f))
+        ret = -EIO;
+
     return ret;
 }
 
@@ -7224,6 +7256,10 @@ static int ram_get_page(QEMUFile *f, uint8_t *buf, int len)
     default:
         return -EINVAL;
     }
+
+    if (qemu_file_has_error(f))
+        return -EIO;
+
     return 0;
 }