diff options
Diffstat (limited to 'block.c')
| -rw-r--r-- | block.c | 47 |
1 files changed, 40 insertions, 7 deletions
@@ -1422,8 +1422,10 @@ done: return c; } -static int bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, - QDict *snapshot_options, Error **errp) +static BlockDriverState *bdrv_append_temp_snapshot(BlockDriverState *bs, + int flags, + QDict *snapshot_options, + Error **errp) { /* TODO: extra byte is a hack to ensure MAX_PATH space on Windows. */ char *tmp_filename = g_malloc0(PATH_MAX + 1); @@ -1439,7 +1441,6 @@ static int bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, /* Get the required size from the image */ total_size = bdrv_getlength(bs); if (total_size < 0) { - ret = total_size; error_setg_errno(errp, -total_size, "Could not get image size"); goto out; } @@ -1479,12 +1480,19 @@ static int bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, goto out; } + /* bdrv_append() consumes a strong reference to bs_snapshot (i.e. it will + * call bdrv_unref() on it), so in order to be able to return one, we have + * to increase bs_snapshot's refcount here */ + bdrv_ref(bs_snapshot); bdrv_append(bs_snapshot, bs); + g_free(tmp_filename); + return bs_snapshot; + out: QDECREF(snapshot_options); g_free(tmp_filename); - return ret; + return NULL; } /* @@ -1704,17 +1712,42 @@ static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename, } QDECREF(options); - *pbs = bs; /* For snapshot=on, create a temporary qcow2 overlay. bs points to the * temporary snapshot afterwards. */ if (snapshot_flags) { - ret = bdrv_append_temp_snapshot(bs, snapshot_flags, snapshot_options, - &local_err); + BlockDriverState *snapshot_bs; + snapshot_bs = bdrv_append_temp_snapshot(bs, snapshot_flags, + snapshot_options, &local_err); snapshot_options = NULL; if (local_err) { + ret = -EINVAL; goto close_and_fail; } + if (!*pbs) { + /* We are not going to return bs but the overlay on top of it + * (snapshot_bs); thus, we have to drop the strong reference to bs + * (which we obtained by calling bdrv_new()). bs will not be + * deleted, though, because the overlay still has a reference to it. + */ + bdrv_unref(bs); + bs = snapshot_bs; + } else { + /* We are not going to return snapshot_bs, so we have to drop the + * strong reference to it (which was returned by + * bdrv_append_temp_snapshot()). snapshot_bs will not be deleted, + * though, because bdrv_append_temp_snapshot() made all parental + * references to bs (*pbs) point to snapshot_bs. + * In fact, if *pbs was not NULL, we are not going to return any new + * BDS. But we do not need to decrement bs's refcount here as is + * done above, because with a non-NULL *pbs this function never even + * had a strong reference to bs. */ + bdrv_unref(snapshot_bs); + } + } + + if (!*pbs) { + *pbs = bs; } return 0; |