block: driver should override flags in bdrv_open()
The BDRV_O_PROTOCOL flag should have an impact only if no driver is
specified explicitly. Therefore, if bdrv_open() is called with an
explicit block driver argument (either through the options QDict or
through the drv parameter) and that block driver is a protocol block
driver, BDRV_O_PROTOCOL should be set; if it is a format block driver,
BDRV_O_PROTOCOL should be unset.
While there was code to unset the flag in case a format block driver
has been selected, it only followed the bdrv_fill_options() function
call whereas the flag in fact needs to be adjusted before it is used
there.
With that change, BDRV_O_PROTOCOL will always be set if the BDS should
be a protocol driver; if the driver has been specified explicitly, the
new code will set it; and bdrv_fill_options() will only "probe" a
protocol driver if BDRV_O_PROTOCOL is set. The probing after
bdrv_fill_options() cannot select a protocol driver.
Thus, bdrv_open_image() to open BDS.file is never called if a protocol
BDS is about to be created. With that change in turn it is impossible to
call bdrv_open_common() with a protocol drv and file != NULL, which
allows us to remove the bdrv_swap() call.
This change breaks a test case in qemu-iotest 051:
"-drive file=t.qcow2,file.driver=qcow2" now works because the explicitly
specified "qcow2" overrides the BDRV_O_PROTOCOL which is automatically
set for the "file" BDS (and the filename is just passed down).
Therefore, this patch removes that test case.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block.c b/block.c
index 4ea2c4f..b2e784e 100644
--- a/block.c
+++ b/block.c
@@ -806,14 +806,6 @@
}
qdict_del(options, "node-name");
- /* bdrv_open() with directly using a protocol as drv. This layer is already
- * opened, so assign it to bs (while file becomes a closed BlockDriverState)
- * and return immediately. */
- if (file != NULL && drv->bdrv_file_open) {
- bdrv_swap(file, bs);
- return 0;
- }
-
bs->open_flags = flags;
bs->guest_block_size = 512;
bs->request_alignment = 512;
@@ -942,14 +934,17 @@
/*
* Fills in default options for opening images and converts the legacy
* filename/flags pair to option QDict entries.
+ * The BDRV_O_PROTOCOL flag in *flags will be set or cleared accordingly if a
+ * block driver has been specified explicitly.
*/
-static int bdrv_fill_options(QDict **options, const char **pfilename, int flags,
- BlockDriver *drv, Error **errp)
+static int bdrv_fill_options(QDict **options, const char **pfilename,
+ int *flags, BlockDriver *drv, Error **errp)
{
const char *filename = *pfilename;
const char *drvname;
- bool protocol = flags & BDRV_O_PROTOCOL;
+ bool protocol = *flags & BDRV_O_PROTOCOL;
bool parse_filename = false;
+ BlockDriver *tmp_drv;
Error *local_err = NULL;
/* Parse json: pseudo-protocol */
@@ -967,6 +962,24 @@
*pfilename = filename = NULL;
}
+ drvname = qdict_get_try_str(*options, "driver");
+
+ /* If the user has explicitly specified the driver, this choice should
+ * override the BDRV_O_PROTOCOL flag */
+ tmp_drv = drv;
+ if (!tmp_drv && drvname) {
+ tmp_drv = bdrv_find_format(drvname);
+ }
+ if (tmp_drv) {
+ protocol = tmp_drv->bdrv_file_open;
+ }
+
+ if (protocol) {
+ *flags |= BDRV_O_PROTOCOL;
+ } else {
+ *flags &= ~BDRV_O_PROTOCOL;
+ }
+
/* Fetch the file name from the options QDict if necessary */
if (protocol && filename) {
if (!qdict_haskey(*options, "filename")) {
@@ -981,7 +994,6 @@
/* Find the right block driver */
filename = qdict_get_try_str(*options, "filename");
- drvname = qdict_get_try_str(*options, "driver");
if (drv) {
if (drvname) {
@@ -1317,7 +1329,7 @@
options = qdict_new();
}
- ret = bdrv_fill_options(&options, &filename, flags, drv, &local_err);
+ ret = bdrv_fill_options(&options, &filename, &flags, drv, &local_err);
if (local_err) {
goto fail;
}
@@ -1336,11 +1348,6 @@
}
assert(drvname || !(flags & BDRV_O_PROTOCOL));
- if (drv && !drv->bdrv_file_open) {
- /* If the user explicitly wants a format driver here, we'll need to add
- * another layer for the protocol in bs->file */
- flags &= ~BDRV_O_PROTOCOL;
- }
bs->options = options;
options = qdict_clone_shallow(options);
@@ -1377,6 +1384,12 @@
goto fail;
}
+ /* BDRV_O_PROTOCOL must be set iff a protocol BDS is about to be created */
+ assert(!!(flags & BDRV_O_PROTOCOL) == !!drv->bdrv_file_open);
+ /* file must be NULL if a protocol BDS is about to be created
+ * (the inverse results in an error message from bdrv_open_common()) */
+ assert(!(flags & BDRV_O_PROTOCOL) || !file);
+
/* Open the image */
ret = bdrv_open_common(bs, file, options, flags, drv, &local_err);
if (ret < 0) {
