block: Add Error parameter to bdrv_find_protocol()

The argument given to bdrv_find_protocol() is just a file name, which
makes it difficult for the caller to reconstruct what protocol
bdrv_find_protocol() was hoping to find. This patch adds an Error
parameter to that function to solve this issue.

Suggested-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 1423162705-32065-4-git-send-email-mreitz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block.c

@@ -508,9 +508,8 @@ int bdrv_create_file(const char *filename, QemuOpts *opts, Error **errp)
     Error *local_err = NULL;
     int ret;
 
-    drv = bdrv_find_protocol(filename, true);
+    drv = bdrv_find_protocol(filename, true, errp);
     if (drv == NULL) {
-        error_setg(errp, "Could not find protocol for file '%s'", filename);
         return -ENOENT;
     }
 
@@ -628,7 +627,8 @@ static BlockDriver *find_hdev_driver(const char *filename)
 }
 
 BlockDriver *bdrv_find_protocol(const char *filename,
-                                bool allow_protocol_prefix)
+                                bool allow_protocol_prefix,
+                                Error **errp)
 {
     BlockDriver *drv1;
     char protocol[128];
@@ -666,6 +666,8 @@ BlockDriver *bdrv_find_protocol(const char *filename,
             return drv1;
         }
     }
+
+    error_setg(errp, "Unknown protocol '%s'", protocol);
     return NULL;
 }
 
@@ -1136,9 +1138,8 @@ static int bdrv_fill_options(QDict **options, const char **pfilename, int flags,
     } else {
         if (!drvname && protocol) {
             if (filename) {
-                drv = bdrv_find_protocol(filename, parse_filename);
+                drv = bdrv_find_protocol(filename, parse_filename, errp);
                 if (!drv) {
-                    error_setg(errp, "Unknown protocol");
                     return -EINVAL;
                 }
 
@@ -5623,9 +5624,8 @@ void bdrv_img_create(const char *filename, const char *fmt,
         return;
     }
 
-    proto_drv = bdrv_find_protocol(filename, true);
+    proto_drv = bdrv_find_protocol(filename, true, errp);
     if (!proto_drv) {
-        error_setg(errp, "Unknown protocol '%s'", filename);
         return;
     }
 

block/sheepdog.c

@@ -1730,7 +1730,7 @@ static int sd_create(const char *filename, QemuOpts *opts,
         BlockDriver *drv;
 
         /* Currently, only Sheepdog backing image is supported. */
-        drv = bdrv_find_protocol(backing_file, true);
+        drv = bdrv_find_protocol(backing_file, true, NULL);
         if (!drv || strcmp(drv->protocol_name, "sheepdog") != 0) {
             error_setg(errp, "backing_file must be a sheepdog image");
             ret = -EINVAL;

include/block/block.h

@@ -168,7 +168,8 @@ void bdrv_io_limits_disable(BlockDriverState *bs);
 void bdrv_init(void);
 void bdrv_init_with_whitelist(void);
 BlockDriver *bdrv_find_protocol(const char *filename,
-                                bool allow_protocol_prefix);
+                                bool allow_protocol_prefix,
+                                Error **errp);
 BlockDriver *bdrv_find_format(const char *format_name);
 BlockDriver *bdrv_find_whitelisted_format(const char *format_name,
                                           bool readonly);

qemu-img.c

@@ -261,6 +261,7 @@ static int print_block_option_help(const char *filename, const char *fmt)
 {
     BlockDriver *drv, *proto_drv;
     QemuOptsList *create_opts = NULL;
+    Error *local_err = NULL;
 
     /* Find driver and parse its options */
     drv = bdrv_find_format(fmt);
@@ -271,9 +272,10 @@ static int print_block_option_help(const char *filename, const char *fmt)
 
     create_opts = qemu_opts_append(create_opts, drv->create_opts);
     if (filename) {
-        proto_drv = bdrv_find_protocol(filename, true);
+        proto_drv = bdrv_find_protocol(filename, true, &local_err);
         if (!proto_drv) {
-            error_report("Unknown protocol '%s'", filename);
+            qerror_report_err(local_err);
+            error_free(local_err);
             qemu_opts_free(create_opts);
             return 1;
         }
@@ -1524,9 +1526,10 @@ static int img_convert(int argc, char **argv)
         goto out;
     }
 
-    proto_drv = bdrv_find_protocol(out_filename, true);
+    proto_drv = bdrv_find_protocol(out_filename, true, &local_err);
     if (!proto_drv) {
-        error_report("Unknown protocol '%s'", out_filename);
+        qerror_report_err(local_err);
+        error_free(local_err);
         ret = -1;
         goto out;
     }

tests/qemu-iotests/051.out

@@ -323,10 +323,10 @@ QEMU_PROG: -drive file=TEST_DIR/t.qcow2,readonly=on,read-only=off: 'read-only' a
 === Parsing protocol from file name ===
 
 Testing: -hda foo:bar
-QEMU_PROG: -hda foo:bar: could not open disk image foo:bar: Unknown protocol
+QEMU_PROG: -hda foo:bar: could not open disk image foo:bar: Unknown protocol 'foo'
 
 Testing: -drive file=foo:bar
-QEMU_PROG: -drive file=foo:bar: could not open disk image foo:bar: Unknown protocol
+QEMU_PROG: -drive file=foo:bar: could not open disk image foo:bar: Unknown protocol 'foo'
 
 Testing: -drive file.filename=foo:bar
 QEMU_PROG: -drive file.filename=foo:bar: could not open disk image ide0-hd0: Could not open 'foo:bar': No such file or directory