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block: pass the right options for BlockDriver.bdrv_open()

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raw_open() expects the caller always passing in the right actual
@options parameter. But when trying to applying snapshot on a RBD
image, bdrv_snapshot_goto() calls raw_open() (by calling the
bdrv_open callback on the BlockDriver) with a NULL @options, and
that will result in a Segmentation fault.

For the other non-raw format drivers, it also makes sense to passing
in the actual options, althought they don't trigger the problem so
far.

Let's prepare a @options by adding the "file" key-value pair to a
copy of the actual options that were given for the node (i.e.
bs->options), and pass it to the callback.

BlockDriver.bdrv_open() expects bs->file to be NULL and just
overwrites it with the result from bdrv_open_child(). That means we
should actually make sure it's NULL because otherwise the child BDS
will have a reference count that is 1 too high. So we unconditionally
invoke bdrv_unref_child() before calling BlockDriver.bdrv_open(), and
we wrap everything in bdrv_ref()/bdrv_unref() so the BDS isn't
deleted in the meantime.

Suggested-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Message-id: 20170405091909.36357-2-bjsdjshi@linux.vnet.ibm.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Dong Jia Shi 2017-04-05 11:19:09 +02:00 committed by Max Reitz
parent aa388ddc36
commit 7a9e51198c
1 changed files with 23 additions and 3 deletions
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26
block/snapshot.c
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@ -27,6 +27,7 @@
#include "block/block_int.h"
#include "qapi/error.h"
#include "qapi/qmp/qerror.h"
#include "qapi/qmp/qstring.h"
QemuOptsList internal_snapshot_opts = {
.name = "snapshot",
@ -189,14 +190,33 @@ int bdrv_snapshot_goto(BlockDriverState *bs,
}
if (bs->file) {
BlockDriverState *file;
QDict *options = qdict_clone_shallow(bs->options);
QDict *file_options;
file = bs->file->bs;
/* Prevent it from getting deleted when detached from bs */
bdrv_ref(file);
qdict_extract_subqdict(options, &file_options, "file.");
QDECREF(file_options);
qdict_put(options, "file", qstring_from_str(bdrv_get_node_name(file)));
drv->bdrv_close(bs);
ret = bdrv_snapshot_goto(bs->file->bs, snapshot_id);
open_ret = drv->bdrv_open(bs, NULL, bs->open_flags, NULL);
bdrv_unref_child(bs, bs->file);
bs->file = NULL;
ret = bdrv_snapshot_goto(file, snapshot_id);
open_ret = drv->bdrv_open(bs, options, bs->open_flags, NULL);
QDECREF(options);
if (open_ret < 0) {
bdrv_unref(bs->file->bs);
bdrv_unref(file);
bs->drv = NULL;
return open_ret;
}
assert(bs->file->bs == file);
bdrv_unref(file);
return ret;
}