From 7a9e51198c24a576275cf509a110d24d7c6ca664 Mon Sep 17 00:00:00 2001 From: Dong Jia Shi Date: Wed, 5 Apr 2017 11:19:09 +0200 Subject: 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: Max Reitz Signed-off-by: Dong Jia Shi Message-id: 20170405091909.36357-2-bjsdjshi@linux.vnet.ibm.com Signed-off-by: Max Reitz --- block/snapshot.c | 26 +++++++++++++++++++++++--- 1 file changed, 23 insertions(+), 3 deletions(-) diff --git a/block/snapshot.c b/block/snapshot.c index bf5c2ca5e1..06b1185d27 100644 --- a/block/snapshot.c +++ b/block/snapshot.c @@ -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; } -- cgit v1.2.1