diff options
| -rw-r--r-- | blockdev.c | 35 | ||||
| -rw-r--r-- | qapi/block-core.json | 39 |
2 files changed, 50 insertions, 24 deletions
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); diff --git a/qapi/block-core.json b/qapi/block-core.json index e34796d98f..0345f6f2d2 100644 --- a/qapi/block-core.json +++ b/qapi/block-core.json @@ -1569,6 +1569,18 @@ # Live commit of data from overlay image nodes into backing nodes - i.e., # writes data between 'top' and 'base' into 'base'. # +# If top == base, that is an error. +# If top has no overlays on top of it, or if it is in use by a writer, +# the job will not be completed by itself. The user needs to complete +# the job with the block-job-complete command after getting the ready +# event. (Since 2.0) +# +# If the base image is smaller than top, then the base image will be +# resized to be the same size as top. If top is smaller than the base +# image, the base will not be truncated. If you want the base image +# size to match the size of the smaller top, you can safely truncate +# it yourself once the commit operation successfully completes. +# # @job-id: identifier for the newly-created block job. If # omitted, the device name will be used. (Since 2.7) # @@ -1593,14 +1605,15 @@ # accepted # # @backing-file: The backing file string to write into the overlay -# image of 'top'. If 'top' is the active layer, -# specifying a backing file string is an error. This -# filename is not validated. +# image of 'top'. If 'top' does not have an overlay +# image, or if 'top' is in use by a writer, specifying +# a backing file string is an error. # -# If a pathname string is such that it cannot be -# resolved by QEMU, that means that subsequent QMP or -# HMP commands must use node-names for the image in -# question, as filename lookup methods will fail. +# This filename is not validated. If a pathname string +# is such that it cannot be resolved by QEMU, that +# means that subsequent QMP or HMP commands must use +# node-names for the image in question, as filename +# lookup methods will fail. # # If not specified, QEMU will automatically determine # the backing file string to use, or error out if @@ -1609,18 +1622,6 @@ # filename or protocol. # (Since 2.1) # -# If top == base, that is an error. -# If top == active, the job will not be completed by itself, -# user needs to complete the job with the block-job-complete -# command after getting the ready event. (Since 2.0) -# -# If the base image is smaller than top, then the base image -# will be resized to be the same size as top. If top is -# smaller than the base image, the base will not be -# truncated. If you want the base image size to match the -# size of the smaller top, you can safely truncate it -# yourself once the commit operation successfully completes. -# # @speed: the maximum speed, in bytes per second # # @on-error: the action to take on an error. 'ignore' means that the request |