We need this blk only for probing - let's create it only when we are going to probe.
That's significant for further changes: we'll need to avoid permission update during open() when possible (to refresh them later of course). But blk_unref() leads to permission update. Instead of implementing extra logic to avoid permission update during blk_unref when we want it, let's just drop blk_unref() from normal code path. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@openvz.org> --- block.c | 48 +++++++++++++++++++++++++----------------------- 1 file changed, 25 insertions(+), 23 deletions(-) diff --git a/block.c b/block.c index 40f54fe121..5a4b59eb6c 100644 --- a/block.c +++ b/block.c @@ -1821,7 +1821,7 @@ QemuOptsList bdrv_create_opts_simple = { * * Removes all processed options from *options. */ -static int bdrv_open_common(BlockDriverState *bs, BlockBackend *file, +static int bdrv_open_common(BlockDriverState *bs, BlockDriverState *file, QDict *options, Error **errp) { int ret, open_flags; @@ -1861,8 +1861,8 @@ static int bdrv_open_common(BlockDriverState *bs, BlockBackend *file, } if (file != NULL) { - bdrv_refresh_filename(blk_bs(file)); - filename = blk_bs(file)->filename; + bdrv_refresh_filename(file); + filename = file->filename; } else { /* * Caution: while qdict_get_try_str() is fine, getting @@ -3883,7 +3883,7 @@ static BlockDriverState *bdrv_open_inherit(const char *filename, Error **errp) { int ret; - BlockBackend *file = NULL; + BlockDriverState *file_bs = NULL; BlockDriverState *bs; BlockDriver *drv = NULL; BdrvChild *child; @@ -4016,8 +4016,6 @@ static BlockDriverState *bdrv_open_inherit(const char *filename, * probing, the block drivers will do their own bdrv_open_child() for the * same BDS, which is why we put the node name back into options. */ if ((flags & BDRV_O_PROTOCOL) == 0) { - BlockDriverState *file_bs; - file_bs = bdrv_open_child_bs(filename, options, "file", bs, &child_of_bds, BDRV_CHILD_IMAGE, true, &local_err); @@ -4025,24 +4023,28 @@ static BlockDriverState *bdrv_open_inherit(const char *filename, goto fail; } if (file_bs != NULL) { - /* Not requesting BLK_PERM_CONSISTENT_READ because we're only - * looking at the header to guess the image format. This works even - * in cases where a guest would not see a consistent state. */ - file = blk_new(bdrv_get_aio_context(file_bs), 0, BLK_PERM_ALL); - blk_insert_bs(file, file_bs, &local_err); - bdrv_unref(file_bs); - if (local_err) { - goto fail; - } - qdict_put_str(options, "file", bdrv_get_node_name(file_bs)); } } /* Image format probing */ bs->probed = !drv; - if (!drv && file) { + if (!drv && file_bs) { + /* + * Not requesting BLK_PERM_CONSISTENT_READ because we're only + * looking at the header to guess the image format. This works even + * in cases where a guest would not see a consistent state. + */ + BlockBackend *file = blk_new(bdrv_get_aio_context(file_bs), 0, + BLK_PERM_ALL); + blk_insert_bs(file, file_bs, &local_err); + if (local_err) { + blk_unref(file); + goto fail; + } + ret = find_image_format(file, filename, &drv, &local_err); + blk_unref(file); if (ret < 0) { goto fail; } @@ -4068,17 +4070,17 @@ static BlockDriverState *bdrv_open_inherit(const char *filename, assert(!!(flags & BDRV_O_PROTOCOL) == !!drv->bdrv_file_open); /* file must be NULL if a protocol BDS is about to be created * (the inverse results in an error message from bdrv_open_common()) */ - assert(!(flags & BDRV_O_PROTOCOL) || !file); + assert(!(flags & BDRV_O_PROTOCOL) || !file_bs); /* Open the image */ - ret = bdrv_open_common(bs, file, options, &local_err); + ret = bdrv_open_common(bs, file_bs, options, &local_err); if (ret < 0) { goto fail; } - if (file) { - blk_unref(file); - file = NULL; + if (file_bs) { + bdrv_unref(file_bs); + file_bs = NULL; } /* If there is a backing file, use it */ @@ -4142,7 +4144,7 @@ static BlockDriverState *bdrv_open_inherit(const char *filename, return bs; fail: - blk_unref(file); + bdrv_unref(file_bs); qobject_unref(snapshot_options); qobject_unref(bs->explicit_options); qobject_unref(bs->options); -- 2.35.1