Commit 7a9e5119 authored by Dong Jia Shi's avatar Dong Jia Shi Committed by Max Reitz
Browse files

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



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: default avatarMax Reitz <mreitz@redhat.com>
Signed-off-by: default avatarDong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Message-id: 20170405091909.36357-2-bjsdjshi@linux.vnet.ibm.com
Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
parent aa388ddc

block/snapshot.c

+23 −3
Original line number Diff line number Diff line
@@ -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;

    }