From 05ea385afdfe5d0886265880bfd14d17192beb03 Mon Sep 17 00:00:00 2001 From: Max Reitz Date: Tue, 11 Jun 2019 21:19:26 +0200 Subject: blockdev: Fix active commit choice We have to perform an active commit whenever the top node has a parent that has taken the WRITE permission on it. This means that block-commit's @backing-file parameter is no longer allowed for such nodes, and that users will have to issue a block-job-complete command. Neither should pose a problem in practice, because this case was basically just broken until now. (Since this commit already touches block-commit's documentation, it also moves up the chunk explaining general block-commit behavior that for some reason was situated under @backing-file.) Signed-off-by: Max Reitz --- blockdev.c | 35 ++++++++++++++++++++++++++++++----- 1 file changed, 30 insertions(+), 5 deletions(-) (limited to 'blockdev.c') diff --git a/blockdev.c b/blockdev.c index f308adc9aa..7f2561081e 100644 --- a/blockdev.c +++ b/blockdev.c @@ -2602,6 +2602,7 @@ void qmp_block_commit(bool has_job_id, const char *job_id, const char *device, AioContext *aio_context; Error *local_err = NULL; int job_flags = JOB_DEFAULT; + uint64_t top_perm, top_shared; if (!has_speed) { speed = 0; @@ -2717,14 +2718,38 @@ void qmp_block_commit(bool has_job_id, const char *job_id, const char *device, goto out; } - if (top_bs == bs) { + /* + * Active commit is required if and only if someone has taken a + * WRITE permission on the top node. Historically, we have always + * used active commit for top nodes, so continue that practice + * lest we possibly break clients that rely on this behavior, e.g. + * to later attach this node to a writing parent. + * (Active commit is never really wrong.) + */ + bdrv_get_cumulative_perm(top_bs, &top_perm, &top_shared); + if (top_perm & BLK_PERM_WRITE || + bdrv_skip_filters(top_bs) == bdrv_skip_filters(bs)) + { if (has_backing_file) { - error_setg(errp, "'backing-file' specified," - " but 'top' is the active layer"); + if (bdrv_skip_filters(top_bs) == bdrv_skip_filters(bs)) { + error_setg(errp, "'backing-file' specified," + " but 'top' is the active layer"); + } else { + error_setg(errp, "'backing-file' specified, but 'top' has a " + "writer on it"); + } goto out; } - commit_active_start(has_job_id ? job_id : NULL, bs, base_bs, - job_flags, speed, on_error, + if (!has_job_id) { + /* + * Emulate here what block_job_create() does, because it + * is possible that @bs != @top_bs (the block job should + * be named after @bs, even if @top_bs is the actual + * source) + */ + job_id = bdrv_get_device_name(bs); + } + commit_active_start(job_id, top_bs, base_bs, job_flags, speed, on_error, filter_node_name, NULL, NULL, false, &local_err); } else { BlockDriverState *overlay_bs = bdrv_find_overlay(bs, top_bs); -- cgit v1.2.3