[Qemu-devel] [5474] Fix some issues with QEMUFile

[Anthony Liguori]

Revision: 5474
          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=5474
Author:   aliguori
Date:     2008-10-13 03:07:56 +0000 (Mon, 13 Oct 2008)

Log Message:
-----------
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: Anthony Liguori <address@hidden>

Modified Paths:
--------------
    trunk/hw/hw.h
    trunk/vl.c

Modified: trunk/hw/hw.h
===================================================================
--- trunk/hw/hw.h       2008-10-12 23:32:59 UTC (rev 5473)
+++ trunk/hw/hw.h       2008-10-13 03:07:56 UTC (rev 5474)
@@ -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_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

Modified: trunk/vl.c
===================================================================
--- trunk/vl.c  2008-10-12 23:32:59 UTC (rev 5473)
+++ trunk/vl.c  2008-10-13 03:07:56 UTC (rev 5474)
@@ -6197,12 +6197,15 @@
     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 @@
     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 @@
         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 @@
     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 @@
     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 @@
     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 @@
     if (!f->get_buffer)
         return;
 
+    if (f->is_write)
+        abort();
+
     len = f->get_buffer(f->opaque, f->buf, f->buf_offset, IO_BUF_SIZE);
-    if (len < 0)
-        len = 0;
-
-    f->buf_index = 0;
-    f->buf_size = len;
-    f->buf_offset += len;
+    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_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_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 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_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 @@
         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 @@
     if (ret)
         return 1;
 
+    if (qemu_file_has_error(f))
+        return -EIO;
+
     return 0;
 }
 
@@ -6734,6 +6752,9 @@
 
     qemu_put_byte(f, QEMU_VM_EOF);
 
+    if (qemu_file_has_error(f))
+        return -EIO;
+
     return 0;
 }
 
@@ -6758,8 +6779,12 @@
     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 @@
         /* 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 @@
         qemu_free(le);
     }
 
+    if (qemu_file_has_error(f))
+        ret = -EIO;
+
     return ret;
 }
 
@@ -7224,6 +7256,10 @@
     default:
         return -EINVAL;
     }
+
+    if (qemu_file_has_error(f))
+        return -EIO;
+
     return 0;
 }