diff options
| -rw-r--r-- | block/qcow2.c | 21 |
1 files changed, 16 insertions, 5 deletions
diff --git a/block/qcow2.c b/block/qcow2.c index c8fc3a6160..6c8c8b2b5a 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -1697,16 +1697,27 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options, ret = -EINVAL; goto fail; } + + s->image_backing_file = g_malloc(len + 1); ret = bdrv_pread(bs->file, header.backing_file_offset, len, - bs->auto_backing_file, 0); + s->image_backing_file, 0); if (ret < 0) { error_setg_errno(errp, -ret, "Could not read backing file name"); goto fail; } - bs->auto_backing_file[len] = '\0'; - pstrcpy(bs->backing_file, sizeof(bs->backing_file), - bs->auto_backing_file); - s->image_backing_file = g_strdup(bs->auto_backing_file); + s->image_backing_file[len] = '\0'; + + /* + * Update only when something has changed. This function is called by + * qcow2_co_invalidate_cache(), and we do not want to reset + * auto_backing_file unless necessary. + */ + if (!g_str_equal(s->image_backing_file, bs->backing_file)) { + pstrcpy(bs->backing_file, sizeof(bs->backing_file), + s->image_backing_file); + pstrcpy(bs->auto_backing_file, sizeof(bs->auto_backing_file), + s->image_backing_file); + } } /* |