[Qemu-devel] [PATCH v3] blockdev: clean up error handling in do_open_tray

[Colin Lord <clord@redhat.com>]

Returns negative error codes and accompanying error messages in cases where
the device has no tray or the tray is locked and isn't forced open. This
extra information should result in better flexibility in functions that
call do_open_tray.

Signed-off-by: Colin Lord <clord@redhat.com>
Suggested by: Markus Armbruster <armbru@redhat.com>
---
 blockdev.c | 46 ++++++++++++++++++++++++++++------------------
 1 file changed, 28 insertions(+), 18 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 717785e..7dd14b9 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -56,6 +56,8 @@
 static QTAILQ_HEAD(, BlockDriverState) monitor_bdrv_states =
     QTAILQ_HEAD_INITIALIZER(monitor_bdrv_states);
 
+static int do_open_tray(const char *device, bool force, Error **errp);
+
 static const char *const if_name[IF_COUNT] = {
     [IF_NONE] = "none",
     [IF_IDE] = "ide",
@@ -2274,8 +2276,6 @@ exit:
     block_job_txn_unref(block_job_txn);
 }
 
-static int do_open_tray(const char *device, bool force, Error **errp);
-
 void qmp_eject(const char *device, bool has_force, bool force, Error **errp)
 {
     Error *local_err = NULL;
@@ -2286,16 +2286,11 @@ void qmp_eject(const char *device, bool has_force, bool force, Error **errp)
     }
 
     rc = do_open_tray(device, force, &local_err);
-    if (local_err) {
+    if (rc && rc != -ENOSYS) {
         error_propagate(errp, local_err);
         return;
     }
-
-    if (rc == EINPROGRESS) {
-        error_setg(errp, "Device '%s' is locked and force was not specified, "
-                   "wait for tray to open and try again", device);
-        return;
-    }
+    error_free(local_err);
 
     qmp_x_blockdev_remove_medium(device, errp);
 }
@@ -2324,11 +2319,16 @@ void qmp_block_passwd(bool has_device, const char *device,
     aio_context_release(aio_context);
 }
 
-/**
- * returns -errno on fatal error, +errno for non-fatal situations.
- * errp will always be set when the return code is negative.
- * May return +ENOSYS if the device has no tray,
- * or +EINPROGRESS if the tray is locked and the guest has been notified.
+/*
+ * Attempt to open the tray of @device.
+ * If @force, ignore its tray lock.
+ * Else, if the tray is locked, don't open it, but ask the guest to open it.
+ * On error, store an error through @errp and return -errno.
+ * If @device does not exist, return -ENODEV.
+ * If it has no removable media, return -ENOTSUP.
+ * If it has no tray, return -ENOSYS.
+ * If the guest was asked to open the tray, return -EINPROGRESS.
+ * Else, return 0.
  */
 static int do_open_tray(const char *device, bool force, Error **errp)
 {
@@ -2348,8 +2348,8 @@ static int do_open_tray(const char *device, bool force, Error **errp)
     }
 
     if (!blk_dev_has_tray(blk)) {
-        /* Ignore this command on tray-less devices */
-        return ENOSYS;
+        error_setg(errp, "Device '%s' does not have a tray", device);
+        return -ENOSYS;
     }
 
     if (blk_dev_is_tray_open(blk)) {
@@ -2366,7 +2366,9 @@ static int do_open_tray(const char *device, bool force, Error **errp)
     }
 
     if (locked && !force) {
-        return EINPROGRESS;
+        error_setg(errp, "Device '%s' is locked and force was not specified, "
+                   "wait for tray to open and try again", device);
+        return -EINPROGRESS;
     }
 
     return 0;
@@ -2375,10 +2377,18 @@ static int do_open_tray(const char *device, bool force, Error **errp)
 void qmp_blockdev_open_tray(const char *device, bool has_force, bool force,
                             Error **errp)
 {
+    Error *local_err = NULL;
+    int rc;
+
     if (!has_force) {
         force = false;
     }
-    do_open_tray(device, force, errp);
+    rc = do_open_tray(device, force, &local_err);
+    if (rc && rc != -ENOSYS && rc != -EINPROGRESS) {
+        error_propagate(errp, local_err);
+        return;
+    }
+    error_free(local_err);
 }
 
 void qmp_blockdev_close_tray(const char *device, Error **errp)
-- 
2.5.5