commit: Add top-node/base-node options
cover commit: Add top-node/base-node options
Kevin Wolf (2):
commit: Add top-node/base-node options
qemu-iotests: Test commit with top-node/base-node
qapi/block-core.json | 24 +++++++++++++++------ blockdev.c | 32 ++++++++++++++++++++++++++-- tests/qemu-iotests/040 | 52 ++++++++++++++++++++++++++++++++++++++++++++-- tests/qemu-iotests/040.out | 4 ++-- 4 files changed, 100 insertions(+), 12 deletions(-)
Signature · 1 line
2.13.6
PATCH 1/2 commit: Add top-node/base-node options
The block-commit QMP command required specifying the top and base nodes of the commit jobs using the file name of that node. While this works in simple cases (local files with absolute paths), the file names generated for more complicated setups can be hard to predict.
This adds two new options top-node and base-node to the command, which allow specifying node names instead. They are mutually exclusive with the old options.
--- qapi/block-core.json | 24 ++++++++++++++++++------ blockdev.c | 32 ++++++++++++++++++++++++++++++-- 2 files changed, 48 insertions(+), 8 deletions(-)
qapi/block-core.json +18 -6
@@ -1455,12 +1455,23 @@ # # @device: the device name or node-name of a root node # -# @base: The file name of the backing image to write data into. -# If not specified, this is the deepest backing image. +# @base-node: The node name of the backing image to write data into. +# If not specified, this is the deepest backing image. +# (since: 2.10) # -# @top: The file name of the backing image within the image chain, -# which contains the topmost data to be committed down. If -# not specified, this is the active layer. +# @base: Same as @base-node, except that it is a file name rather than a node +# name. This must be the exact filename string that was used to open the +# node; other strings, even if addressing the same file, are not +# accepted (deprecated, use @base-node instead) +# +# @top-node: The node name of the backing image within the image chain +# which contains the topmost data to be committed down. If +# not specified, this is the active layer. (since: 2.10) +# +# @top: Same as @top-node, except that it is a file name rather than a node +# name. This must be the exact filename string that was used to open the +# node; other strings, even if addressing the same file, are not +# accepted (deprecated, use @base-node instead) # # @backing-file: The backing file string to write into the overlay # image of 'top'. If 'top' is the active layer,
@@ -1516,7 +1527,8 @@ # ## { 'command': 'block-commit', - 'data': { '*job-id': 'str', 'device': 'str', '*base': 'str', '*top': 'str', + 'data': { '*job-id': 'str', 'device': 'str', '*base-node': 'str', + '*base': 'str', '*top-node': 'str', '*top': 'str', '*backing-file': 'str', '*speed': 'int', '*filter-node-name': 'str' } }
blockdev.c +30 -2
@@ -3308,7 +3308,9 @@ out: } void qmp_block_commit(bool has_job_id, const char *job_id, const char *device, + bool has_base_node, const char *base_node, bool has_base, const char *base, + bool has_top_node, const char *top_node, bool has_top, const char *top, bool has_backing_file, const char *backing_file, bool has_speed, int64_t speed,
@@ -3360,7 +3362,20 @@ void qmp_block_commit(bool has_job_id, const char *job_id, const char *device,/* default top_bs is the active layer */ top_bs = bs; -if (has_top && top) { +if (has_top_node && has_top) { +error_setg (errp,"'top-node' and 'top' are mutually exclusive" ); + goto out; + }else if (has_top_node) { + top_bs =bdrv_lookup_bs (NULL , top_node, errp); +if (top_bs ==NULL ) { + goto out; + } +if (!bdrv_chain_contains (bs, top_bs)) { +error_setg (errp,"'%s' is not in this backing file chain" , + top_node); + goto out; + } + }else if (has_top && top) {if (strcmp (bs->filename, top) !=0 ) { top_bs =bdrv_find_backing_image (bs, top); }
@@ -3373,7 +3388,20 @@ void qmp_block_commit(bool has_job_id, const char *job_id, const char *device,assert (bdrv_get_aio_context (top_bs) == aio_context); -if (has_base && base) { +if (has_base_node && has_base) { +error_setg (errp,"'base-node' and 'base' are mutually exclusive" ); + goto out; + }else if (has_base_node) { + base_bs =bdrv_lookup_bs (NULL , base_node, errp); +if (base_bs ==NULL ) { + goto out; + } +if (!bdrv_chain_contains (top_bs, base_bs)) { +error_setg (errp,"'%s' is not in this backing file chain" , + base_node); + goto out; + } + }else if (has_base && base) { base_bs =bdrv_find_backing_image (top_bs, base); }else { base_bs =bdrv_find_base (top_bs);
Signature · 1 line
2.13.6
Quoted 20 lines · Kevin Wolf
The block-commit QMP command required specifying the top and base nodes of the commit jobs using the file name of that node. While this works in simple cases (local files with absolute paths), the file names generated for more complicated setups can be hard to predict.
This adds two new options top-node and base-node to the command, which allow specifying node names instead. They are mutually exclusive with the old options.
Signed-off-by Kevin Wolf <[email protected]>--- qapi/block-core.json | 24 ++++++++++++++++++------ blockdev.c | 32 ++++++++++++++++++++++++++++++-- 2 files changed, 48 insertions(+), 8 deletions(-)qapi/block-core.json +0
-0
qapi/block-core.json line 1460
Quoted 8 lines
qapi/block-core.json +3
-2@@ -1455,12 +1455,23 @@ # # @device: the device name or node-name of a root node # -# @base: The file name of the backing image to write data into. -# If not specified, this is the deepest backing image. +# @base-node: The node name of the backing image to write data into. +# If not specified, this is the deepest backing image. +# (since: 2.10)
I'd word this as (since 3.1)...
qapi/block-core.json line 1465
Quoted 8 lines
qapi/block-core.json +4
-3# -# @top: The file name of the backing image within the image chain, -# which contains the topmost data to be committed down. If -# not specified, this is the active layer. +# @base: Same as @base-node, except that it is a file name rather than a node +# name. This must be the exact filename string that was used to open the +# node; other strings, even if addressing the same file, are not +# accepted (deprecated, use @base-node instead)
...and this as (since 2.10). When we finish the deprecation and remove @base, then we might consolidate the 'since' documentation at that time, but until then, I think listing the two separate releases gives users an idea of how far back they might have been using the deprecated code, and when the preferred form was introduced.
qapi/block-core.json line 1474
Quoted 9 lines
qapi/block-core.json +9
-0+# +# @top-node: The node name of the backing image within the image chain +# which contains the topmost data to be committed down. If +# not specified, this is the active layer. (since: 2.10) +# +# @top: Same as @top-node, except that it is a file name rather than a node +# name. This must be the exact filename string that was used to open the +# node; other strings, even if addressing the same file, are not +# accepted (deprecated, use @base-node instead)
Likewise.
Actually, do we NEED new arguments? Can we just make @base and @top accept either an exact file name OR a node name? On the other hand, new arguments are introspectible, overloading the old argument to take two forms is not. So that doesn't help :(
Or, here's an idea:
Keep the name @base and @top, but add a new '*by-node':'bool' parameter, defaulting to false for now, but perhaps with a deprecation warning that we'll switch the default to true in one release and delete the parameter altogether in an even later release. When false, @base and @top are filenames, as before; when true, @base and @top are node names instead. Introspectible, nicer names in the long run, and avoids having to detect a user providing two mutually-exclusive options at once.
qapi/block-core.json out: · line 3316
Quoted 11 lines
qapi/block-core.json +3
-0+++ b/blockdev.c@@ -3308,7 +3308,9 @@ out: } void qmp_block_commit(bool has_job_id, const char *job_id, const char *device, + bool has_base_node, const char *base_node, bool has_base, const char *base, + bool has_top_node, const char *top_node, bool has_top, const char *top, bool has_backing_file, const char *backing_file, bool has_speed, int64_t speed,
Getting to be a long signature. Should we use 'boxed':true in the QAPI file to make this easier to write? (Separate commit)
Signature · 3 lines
Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
Am 10.08.2018 um 19:33 hat Eric Blake geschrieben:
Quoted 16 lines · Kevin Wolf
Quoted 15 lines
The block-commit QMP command required specifying the top and base nodes of the commit jobs using the file name of that node. While this works in simple cases (local files with absolute paths), the file names generated for more complicated setups can be hard to predict.
This adds two new options top-node and base-node to the command, which allow specifying node names instead. They are mutually exclusive with the old options.
Signed-off-by Kevin Wolf <[email protected]>--- qapi/block-core.json | 24 ++++++++++++++++++------ blockdev.c | 32 ++++++++++++++++++++++++++++++-- 2 files changed, 48 insertions(+), 8 deletions(-)
Quoted 15 lines
qapi/block-core.json line 1460
Quoted 13 lines
qapi/block-core.json +3
-2@@ -1455,12 +1455,23 @@ # # @device: the device name or node-name of a root node # -# @base: The file name of the backing image to write data into. -# If not specified, this is the deepest backing image. +# @base-node: The node name of the backing image to write data into. +# If not specified, this is the deepest backing image. +# (since: 2.10)I'd word this as (since 3.1)...
Whoops. Apparently I didn't read the documentation change carefully enough when resurrecting this patch from an old branch.
Quoted 10 lines
qapi/block-core.json line 1465
Quoted 8 lines
qapi/block-core.json +4
-3# -# @top: The file name of the backing image within the image chain, -# which contains the topmost data to be committed down. If -# not specified, this is the active layer. +# @base: Same as @base-node, except that it is a file name rather than a node +# name. This must be the exact filename string that was used to open the +# node; other strings, even if addressing the same file, are not +# accepted (deprecated, use @base-node instead)...and this as (since 2.10).
No, 2.10 is just completely wrong. @base exists since the command was introduced, which is commit ed61fc10e8c or QEMU 1.3.
Quoted 5 lines
When we finish the deprecation and remove @base, then we might consolidate the 'since' documentation at that time, but until then, I think listing the two separate releases gives users an idea of how far back they might have been using the deprecated code, and when the preferred form was introduced.
Yes, obviously.
Quoted 12 lines
qapi/block-core.json line 1474
Quoted 9 lines
qapi/block-core.json +9
-0+# +# @top-node: The node name of the backing image within the image chain +# which contains the topmost data to be committed down. If +# not specified, this is the active layer. (since: 2.10) +# +# @top: Same as @top-node, except that it is a file name rather than a node +# name. This must be the exact filename string that was used to open the +# node; other strings, even if addressing the same file, are not +# accepted (deprecated, use @base-node instead)Likewise.
Quoted 2 lines
Actually, do we NEED new arguments? Can we just make @base and @top accept either an exact file name OR a node name?
No, no, no, no, no!
You can't tell whether "foo" is a file name or a node name, and they could both exist at the same time, so it would be ambiguous. We should avoid mixing semantically different things in a single field whenever it's possible.
The reason why node name and BlockBackend name can be used in the same option is that they share a name space, i.e. if there is already a node name "foo", trying to create a BlockBackend "foo" will fail, and vice versa.
Quoted 3 lines
On the other hand, new arguments are introspectible, overloading the old argument to take two forms is not.
So that doesn't help :(
That, too, yes.
Quoted 9 lines
Or, here's an idea:
Keep the name @base and @top, but add a new '*by-node':'bool' parameter, defaulting to false for now, but perhaps with a deprecation warning that we'll switch the default to true in one release and delete the parameter altogether in an even later release. When false, @base and @top are filenames, as before; when true, @base and @top are node names instead. Introspectible, nicer names in the long run, and avoids having to detect a user providing two mutually-exclusive options at once.
I don't like options that completely change the semantics of other options, but maybe that's just personal preference.
Anyway, thinking about the long term for block-commit is useless, the command is just broken (for example, the @device option doesn't make any sense) and will have to be replaced. But libvirt needs something _now_ for the -blockdev support, so I decided to add this as a quick hack before we get the proper replacement.
I think it makes more sense to create a new blockdev-commit (which would be a name more in line with the other block job commands) and deprecate the old block-commit command as a whole.
Quoted 5 lines
Quoted 5 lines
qapi/block-core.json +2
-0+++ b/blockdev.c@@ -3308,7 +3308,9 @@ out: } void qmp_block_commit(bool has_job_id, const char *job_id, const char *device, + bool has_base_node, const char *base_node,
Quoted 8 lines
qapi/block-core.json out: · line 3315
Quoted 5 lines
qapi/block-core.json +1
-0bool has_base, const char *base, + bool has_top_node, const char *top_node, bool has_top, const char *top, bool has_backing_file, const char *backing_file, bool has_speed, int64_t speed,Getting to be a long signature. Should we use 'boxed':true in the QAPI file to make this easier to write? (Separate commit)
It's an option.
Has any progress been made on the plan to support defaults in QAPI, so that we could get rid of the has_* parameters?
Kevin
Quoted 21 lines · Kevin Wolf
Am 10.08.2018 um 19:33 hat Eric Blake geschrieben:
Quoted 20 lines · Kevin Wolf
Quoted 19 lines
The block-commit QMP command required specifying the top and base nodes of the commit jobs using the file name of that node. While this works in simple cases (local files with absolute paths), the file names generated for more complicated setups can be hard to predict.
This adds two new options top-node and base-node to the command, which allow specifying node names instead. They are mutually exclusive with the old options.
Signed-off-by Kevin Wolf <[email protected]>--- qapi/block-core.json | 24 ++++++++++++++++++------ blockdev.c | 32 ++++++++++++++++++++++++++++++-- 2 files changed, 48 insertions(+), 8 deletions(-)qapi/block-core.json +0
-0
[...]
Quoted 10 lines
Quoted 9 lines
Or, here's an idea:
Keep the name @base and @top, but add a new '*by-node':'bool' parameter, defaulting to false for now, but perhaps with a deprecation warning that we'll switch the default to true in one release and delete the parameter altogether in an even later release. When false, @base and @top are filenames, as before; when true, @base and @top are node names instead. Introspectible, nicer names in the long run, and avoids having to detect a user providing two mutually-exclusive options at once.
Quoted 2 lines
I don't like options that completely change the semantics of other options, but maybe that's just personal preference.
I happen to share it.
Quoted 24 lines
Anyway, thinking about the long term for block-commit is useless, the command is just broken (for example, the @device option doesn't make any sense) and will have to be replaced. But libvirt needs something _now_ for the -blockdev support, so I decided to add this as a quick hack before we get the proper replacement.
I think it makes more sense to create a new blockdev-commit (which would be a name more in line with the other block job commands) and deprecate the old block-commit command as a whole.
Quoted 5 lines
Quoted 5 lines
+++
b/blockdev.cqapi/block-core.json +1
-0@@ -3308,7 +3308,9 @@ out: } void qmp_block_commit(bool has_job_id, const char *job_id, const char *device, + bool has_base_node, const char *base_node,Quoted 8 lines
qapi/block-core.json out: · line 3315
Quoted 5 lines
qapi/block-core.json +1
-0bool has_base, const char *base, + bool has_top_node, const char *top_node, bool has_top, const char *top, bool has_backing_file, const char *backing_file, bool has_speed, int64_t speed,Getting to be a long signature. Should we use 'boxed':true in the QAPI file to make this easier to write? (Separate commit)
Quoted 4 lines
It's an option.
Has any progress been made on the plan to support defaults in QAPI, so that we could get rid of the has_* parameters?
No. It's one of those things that keep getting pushed out by more important or urgent stuff.
I expect it to be straightforward, if tedious.
Quoted 10 lines · Markus Armbruster
Quoted 10 lines
Quoted 9 lines
Or, here's an idea:
Keep the name @base and @top, but add a new '*by-node':'bool' parameter, defaulting to false for now, but perhaps with a deprecation warning that we'll switch the default to true in one release and delete the parameter altogether in an even later release. When false, @base and @top are filenames, as before; when true, @base and @top are node names instead. Introspectible, nicer names in the long run, and avoids having to detect a user providing two mutually-exclusive options at once.
Quoted 4 lines
Quoted 2 lines
I don't like options that completely change the semantics of other options, but maybe that's just personal preference.
I happen to share it.
Okay, we'll ditch that idea as a non-starter.
Quoted 10 lines
Quoted 10 lines
Anyway, thinking about the long term for block-commit is useless, the command is just broken (for example, the @device option doesn't make any sense) and will have to be replaced. But libvirt needs something _now_ for the -blockdev support, so I decided to add this as a quick hack before we get the proper replacement.
I think it makes more sense to create a new blockdev-commit (which would be a name more in line with the other block job commands) and deprecate the old block-commit command as a whole.
Okay, looks like a good plan for the long term, and thus a good rationale for the short-term choices. The commit message could call that out.
Quoted 7 lines
Quoted 2 lines
Has any progress been made on the plan to support defaults in QAPI, so that we could get rid of the has_* parameters?
No. It's one of those things that keep getting pushed out by more important or urgent stuff.
I expect it to be straightforward, if tedious.
In part, Marc-Andre's work to get conditional compilation in has gotten us closer, in that we can have 'name':{'type':'foo','if':'...'} instead of 'name':'type', since that dict for conditional compilation is also where we would stick in default values.
Signature · 3 lines
Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
Quoted 9 lines · Kevin Wolf
The block-commit QMP command required specifying the top and base nodes of the commit jobs using the file name of that node. While this works in simple cases (local files with absolute paths), the file names generated for more complicated setups can be hard to predict.
This adds two new options top-node and base-node to the command, which allow specifying node names instead. They are mutually exclusive with the old options.
Quoted 5 lines
Signed-off-by Kevin Wolf <[email protected]>--- qapi/block-core.json | 24 ++++++++++++++++++------ blockdev.c | 32 ++++++++++++++++++++++++++++++-- 2 files changed, 48 insertions(+), 8 deletions(-)
Looks good to me, but you made me a bit cautious with your talk of how many pitfalls you've encountered on your way to do this change...
Max
Quoted 9 lines · Kevin Wolf
The block-commit QMP command required specifying the top and base nodes of the commit jobs using the file name of that node. While this works in simple cases (local files with absolute paths), the file names generated for more complicated setups can be hard to predict.
This adds two new options top-node and base-node to the command, which allow specifying node names instead. They are mutually exclusive with the old options.
Quoted 5 lines
Signed-off-by Kevin Wolf <[email protected]>--- qapi/block-core.json | 24 ++++++++++++++++++------ blockdev.c | 32 ++++++++++++++++++++++++++++++-- 2 files changed, 48 insertions(+), 8 deletions(-)
While the below is not strictly relevant to this patch usage block-commit is not possible when using -blockdev. Thus the new arguments are not very useful otherwise.
With the new options I'm getting:
{"execute":"block-commit",
"arguments": { "device":"libvirt-3-format",
"job-id":"libvirt-3-format",
"top-node":"libvirt-8-format",
"base-node":"libvirt-9-format",
"auto-finalize":true,
"auto-dismiss":false},"id":"libvirt-16"}
{"id":"libvirt-16",
"error":{"class":"GenericError",
"desc":"Block node is read-only"}}
I'm pointing into the backing chain so the files are declared as read-only.
It works just-fine if I open them as read-write with -blockdev/blockdev-add but that obviously is not correct as you can't then share parts of the backing chain with other VMs due to image locking.
libvirt-3-format is read-write and all other node names are readonly in the above example.
The same also happens when using filenames:
{"execute":"block-commit",
"arguments" : {"device":"libvirt-3-format",
"job-id":"libvirt-3-format",
"top":"/var/lib/libvirt/images/rhel7.3.1483615252",
"base":"/var/lib/libvirt/images/rhel7.3.1483605924",
"auto-finalize":true,
"auto-dismiss":false},"id":"libvirt-13"}
{"id":"libvirt-13","error":{"class":"GenericError","desc":"Block node is read-only"}}
When I use the drive alias rather than the node-name for the 'device' argument it works as expected.
{"execute":"block-commit",
"arguments": { "device":"drive-virtio-disk0",
"job-id":"drive-virtio-disk0",
"top":"/var/lib/libvirt/images/rhel7.3.1483536402",
"base":"/var/lib/libvirt/images/rhel7.3.1483545313"},"id":"libvirt-18"}
I was not able to find anything which would allow to reopen the file R/W in case of the block-commit operation, but I suspect it should be done automatically as previously it was done that way prior to -blockdev.
Peter
Am 28.08.2018 um 16:26 hat Peter Krempa geschrieben:
Quoted 49 lines · Kevin Wolf
Quoted 9 lines
The block-commit QMP command required specifying the top and base nodes of the commit jobs using the file name of that node. While this works in simple cases (local files with absolute paths), the file names generated for more complicated setups can be hard to predict.
This adds two new options top-node and base-node to the command, which allow specifying node names instead. They are mutually exclusive with the old options.
Quoted 5 lines
Signed-off-by Kevin Wolf <[email protected]>--- qapi/block-core.json | 24 ++++++++++++++++++------ blockdev.c | 32 ++++++++++++++++++++++++++++++-- 2 files changed, 48 insertions(+), 8 deletions(-)While the below is not strictly relevant to this patch usage block-commit is not possible when using -blockdev. Thus the new arguments are not very useful otherwise.
With the new options I'm getting:
{"execute":"block-commit",
"arguments": { "device":"libvirt-3-format","job-id":"libvirt-3-format", "top-node":"libvirt-8-format", "base-node":"libvirt-9-format", "auto-finalize":true, "auto-dismiss":false},"id":"libvirt-16"}
{"id":"libvirt-16",
"error":{"class":"GenericError","desc":"Block node is read-only"}}I'm pointing into the backing chain so the files are declared as read-only.
It works just-fine if I open them as read-write with -blockdev/blockdev-add but that obviously is not correct as you can't then share parts of the backing chain with other VMs due to image locking.
libvirt-3-format is read-write and all other node names are readonly in the above example.
The same also happens when using filenames:
{"execute":"block-commit",
"arguments" : {"device":"libvirt-3-format",
Quoted 8 lines
"job-id":"libvirt-3-format", "top":"/var/lib/libvirt/images/rhel7.3.1483615252", "base":"/var/lib/libvirt/images/rhel7.3.1483605924", "auto-finalize":true, "auto-dismiss":false},"id":"libvirt-13"}
{"id":"libvirt-13","error":{"class":"GenericError","desc":"Block node is read-only"}}
I see what's happening here. So we have a graph like this:
guest device
|
v
overlay-format -------> backing-format
[read-only=off] [read-only=on]
| |
v v
overlay-proto backing-proto
[read-only=off] [read-only=on]The difference between your -blockdev use and -drive is that you explicitly specify the read-only option for backing-proto (and you use a separate -blockdev option anyway), so it doesn't just inherit it from backing-format.
Now, when the commit job tries to reopen backing-format, your explicit read-only=on for backing-proto still takes precedence and the node stays read-only. If you hadn't used a separate -blockdev for backing-proto, but included it in the definition for backing-format and left out the read-only option, it would have inherited the option and reopen would adjust both nodes. This is what happens with -drive.
So essentially, I guess, all places that want to switch between read-only and read-write need to learn which other nodes (apart from the top-level node they are interested in) must be reopened as well.
This looks a bit messy. :-/
Any good ideas anyone?
Kevin
Quoted 28 lines · Kevin Wolf
Quoted 7 lines
libvirt-3-format is read-write and all other node names are readonly in the above example.
The same also happens when using filenames:
{"execute":"block-commit",
"arguments" : {"device":"libvirt-3-format",Quoted 8 lines
"job-id":"libvirt-3-format", "top":"/var/lib/libvirt/images/rhel7.3.1483615252", "base":"/var/lib/libvirt/images/rhel7.3.1483605924", "auto-finalize":true, "auto-dismiss":false},"id":"libvirt-13"}
{"id":"libvirt-13","error":{"class":"GenericError","desc":"Block node is read-only"}}
I see what's happening here. So we have a graph like this:
guest device | v overlay-format -------> backing-format [read-only=off] [read-only=on] | | v v overlay-proto backing-proto [read-only=off] [read-only=on]
Quoted 4 lines
The difference between your -blockdev use and -drive is that you explicitly specify the read-only option for backing-proto (and you use a separate -blockdev option anyway), so it doesn't just inherit it from backing-format.
Are these format and protocol block devices opened with four separate -blockdev parameters? Is that how libvirt does it?
Berto
Quoted 29 lines · Alberto Garcia
Quoted 28 lines · Kevin Wolf
Quoted 7 lines
libvirt-3-format is read-write and all other node names are readonly in the above example.
The same also happens when using filenames:
{"execute":"block-commit",
"arguments" : {"device":"libvirt-3-format",Quoted 8 lines
"job-id":"libvirt-3-format", "top":"/var/lib/libvirt/images/rhel7.3.1483615252", "base":"/var/lib/libvirt/images/rhel7.3.1483605924", "auto-finalize":true, "auto-dismiss":false},"id":"libvirt-13"}
{"id":"libvirt-13","error":{"class":"GenericError","desc":"Block node is read-only"}}
I see what's happening here. So we have a graph like this:
guest device | v overlay-format -------> backing-format [read-only=off] [read-only=on] | | v v overlay-proto backing-proto [read-only=off] [read-only=on]
Quoted 7 lines
Quoted 4 lines
The difference between your -blockdev use and -drive is that you explicitly specify the read-only option for backing-proto (and you use a separate -blockdev option anyway), so it doesn't just inherit it from backing-format.
Are these format and protocol block devices opened with four separate -blockdev parameters? Is that how libvirt does it?
Yes. This goes along with the fact that for 'blockdev-create' you need to blockdev-add the file which you want to format, but the formatted file is not automatically added.
If we'd use the approach where the protocol layer is opened as part of the format layer it would complicate the snapshot code where we need to add a file and then format it to qcow2. It would mean that we'd have to blockdev-add a file, format it via blockdev-create, then blockdev-del it and open it together with the format layer. Otherwise the disk hot-unplug code would be plain crazy.
Quoted 40 lines · Peter Krempa
Quoted 28 lines
Quoted 28 lines
Quoted 7 lines
libvirt-3-format is read-write and all other node names are readonly in the above example.
The same also happens when using filenames:
{"execute":"block-commit",
"arguments" : {"device":"libvirt-3-format",Quoted 8 lines
"job-id":"libvirt-3-format", "top":"/var/lib/libvirt/images/rhel7.3.1483615252", "base":"/var/lib/libvirt/images/rhel7.3.1483605924", "auto-finalize":true, "auto-dismiss":false},"id":"libvirt-13"}
{"id":"libvirt-13","error":{"class":"GenericError","desc":"Block node is read-only"}}
I see what's happening here. So we have a graph like this:
guest device | v overlay-format -------> backing-format [read-only=off] [read-only=on] | | v v overlay-proto backing-proto [read-only=off] [read-only=on]Quoted 7 lines
Quoted 4 lines
The difference between your -blockdev use and -drive is that you explicitly specify the read-only option for backing-proto (and you use a separate -blockdev option anyway), so it doesn't just inherit it from backing-format.
Are these format and protocol block devices opened with four separate -blockdev parameters? Is that how libvirt does it?
Yes. This goes along with the fact that for 'blockdev-create' you need to blockdev-add the file which you want to format, but the formatted file is not automatically added.
Quoted 6 lines
If we'd use the approach where the protocol layer is opened as part of the format layer it would complicate the snapshot code where we need to add a file and then format it to qcow2. It would mean that we'd have to blockdev-add a file, format it via blockdev-create, then blockdev-del it and open it together with the format layer. Otherwise the disk hot-unplug code would be plain crazy.
Do you need to add the protocol layer in order to format it, though? :-?
(I'm just trying to understand how this works, I'm not too familiar with blockdev-create)
{'execute': 'blockdev-create',
'arguments': {'job-id': 'job0',
'options': {'driver': 'file',
'filename': 'test.qcow2',
'size': 0}}}{'execute': 'job-dismiss', 'arguments': {'id': 'job0'}}
{'execute': 'blockdev-create',
'arguments': {'job-id': 'job1',
'options': { 'driver': 'qcow2',
'size': 1048576,
'file': {'driver': 'file',
'filename': 'test.qcow2'}}}}{'execute': 'job-dismiss', 'arguments': {'id': 'job1'}}
Berto
Quoted 60 lines · Alberto Garcia
Quoted 40 lines · Peter Krempa
Quoted 28 lines
Quoted 28 lines
Quoted 7 lines
libvirt-3-format is read-write and all other node names are readonly in the above example.
The same also happens when using filenames:
{"execute":"block-commit",
"arguments" : {"device":"libvirt-3-format",Quoted 8 lines
"job-id":"libvirt-3-format", "top":"/var/lib/libvirt/images/rhel7.3.1483615252", "base":"/var/lib/libvirt/images/rhel7.3.1483605924", "auto-finalize":true, "auto-dismiss":false},"id":"libvirt-13"}
{"id":"libvirt-13","error":{"class":"GenericError","desc":"Block node is read-only"}}
I see what's happening here. So we have a graph like this:
guest device | v overlay-format -------> backing-format [read-only=off] [read-only=on] | | v v overlay-proto backing-proto [read-only=off] [read-only=on]Quoted 7 lines
Quoted 4 lines
The difference between your -blockdev use and -drive is that you explicitly specify the read-only option for backing-proto (and you use a separate -blockdev option anyway), so it doesn't just inherit it from backing-format.
Are these format and protocol block devices opened with four separate -blockdev parameters? Is that how libvirt does it?
Yes. This goes along with the fact that for 'blockdev-create' you need to blockdev-add the file which you want to format, but the formatted file is not automatically added.
Quoted 6 lines
If we'd use the approach where the protocol layer is opened as part of the format layer it would complicate the snapshot code where we need to add a file and then format it to qcow2. It would mean that we'd have to blockdev-add a file, format it via blockdev-create, then blockdev-del it and open it together with the format layer. Otherwise the disk hot-unplug code would be plain crazy.
Do you need to add the protocol layer in order to format it, though? :-?
(I'm just trying to understand how this works, I'm not too familiar with blockdev-create)
{'execute': 'blockdev-create',
'arguments': {'job-id': 'job0','options': {'driver': 'file', 'filename': 'test.qcow2', 'size': 0}}}{'execute': 'job-dismiss', 'arguments': {'id': 'job0'}}
Quoted 7 lines
{'execute': 'blockdev-create',
'arguments': {'job-id': 'job1','options': { 'driver': 'qcow2', 'size': 1048576, 'file': {'driver': 'file', 'filename': 'test.qcow2'}}}}{'execute': 'job-dismiss', 'arguments': {'id': 'job1'}}
Honestly I've reused the existing approach and did not try without actually adding the protocol layer.
I remember being told some time ago to specify both layers explicitly. Since it's not yet enabled in libvirt we theoretically could change to one -blockdev for format+protocol but in that case we need some kind of guarantee that every (even new) feature will work with it.
Switching between those approaches once we enable it upstream will not be possible without adding a lot of compatibility code.
Am 04.09.2018 um 17:00 hat Peter Krempa geschrieben:
Quoted 72 lines · Alberto Garcia
Quoted 60 lines · Peter Krempa
Quoted 40 lines
Quoted 28 lines
Quoted 28 lines
Quoted 7 lines
libvirt-3-format is read-write and all other node names are readonly in the above example.
The same also happens when using filenames:
{"execute":"block-commit",
"arguments" : {"device":"libvirt-3-format",Quoted 8 lines
"job-id":"libvirt-3-format", "top":"/var/lib/libvirt/images/rhel7.3.1483615252", "base":"/var/lib/libvirt/images/rhel7.3.1483605924", "auto-finalize":true, "auto-dismiss":false},"id":"libvirt-13"}
{"id":"libvirt-13","error":{"class":"GenericError","desc":"Block node is read-only"}}
I see what's happening here. So we have a graph like this:
guest device | v overlay-format -------> backing-format [read-only=off] [read-only=on] | | v v overlay-proto backing-proto [read-only=off] [read-only=on]Quoted 7 lines
Quoted 4 lines
The difference between your -blockdev use and -drive is that you explicitly specify the read-only option for backing-proto (and you use a separate -blockdev option anyway), so it doesn't just inherit it from backing-format.
Are these format and protocol block devices opened with four separate -blockdev parameters? Is that how libvirt does it?
Yes. This goes along with the fact that for 'blockdev-create' you need to blockdev-add the file which you want to format, but the formatted file is not automatically added.
Quoted 6 lines
If we'd use the approach where the protocol layer is opened as part of the format layer it would complicate the snapshot code where we need to add a file and then format it to qcow2. It would mean that we'd have to blockdev-add a file, format it via blockdev-create, then blockdev-del it and open it together with the format layer. Otherwise the disk hot-unplug code would be plain crazy.
Do you need to add the protocol layer in order to format it, though? :-?
(I'm just trying to understand how this works, I'm not too familiar with blockdev-create)
{'execute': 'blockdev-create',
'arguments': {'job-id': 'job0','options': {'driver': 'file', 'filename': 'test.qcow2', 'size': 0}}}{'execute': 'job-dismiss', 'arguments': {'id': 'job0'}}
Quoted 7 lines
{'execute': 'blockdev-create',
'arguments': {'job-id': 'job1','options': { 'driver': 'qcow2', 'size': 1048576, 'file': {'driver': 'file', 'filename': 'test.qcow2'}}}}{'execute': 'job-dismiss', 'arguments': {'id': 'job1'}}
Honestly I've reused the existing approach and did not try without actually adding the protocol layer.
Quoted 7 lines
I remember being told some time ago to specify both layers explicitly. Since it's not yet enabled in libvirt we theoretically could change to one -blockdev for format+protocol but in that case we need some kind of guarantee that every (even new) feature will work with it.
Switching between those approaches once we enable it upstream will not be possible without adding a lot of compatibility code.
Yeah, I think specifying both layers explicitly is cleaner. This should probably be solved some way inside QEMU.
The read-only option for the backend isn't that useful anyway. Maybe we should do away with it, at least for its current purpose, and just rely on write permissions taken by parents. We could then either silently ignore (and deprecate) the read-only backend option or we could change its semantics to mean "never allow a writer on this node".
Kevin
Quoted 3 lines · Kevin Wolf
Am 04.09.2018 um 17:00 hat Peter Krempa geschrieben:
Quoted 2 lines · Alberto Garcia
Quoted 1 line · Peter Krempa
[...]
Quoted 8 lines
Quoted 7 lines
I remember being told some time ago to specify both layers explicitly. Since it's not yet enabled in libvirt we theoretically could change to one -blockdev for format+protocol but in that case we need some kind of guarantee that every (even new) feature will work with it.
Switching between those approaches once we enable it upstream will not be possible without adding a lot of compatibility code.
Quoted 8 lines
Yeah, I think specifying both layers explicitly is cleaner. This should probably be solved some way inside QEMU.
The read-only option for the backend isn't that useful anyway. Maybe we should do away with it, at least for its current purpose, and just rely on write permissions taken by parents. We could then either silently ignore (and deprecate) the read-only backend option or we could change its semantics to mean "never allow a writer on this node".
So I tried that approach and it seems to work just fine with files including sharing part of the read-only backing chain with other VMs without the image locking mechanism ruining the day.
block-commit is able to reopen the format layers and works as expected.
Unfortunately though the 'read-only' option is actually useful as the curl-driver does not work without it:
-blockdev {"driver":"http","url":"http://ftp.sjtu.edu.cn:80/ubuntu-cd/12.04/ubuntu-12.04.5-alternate-amd64.iso","node-name":"libvirt-2-storage","discard":"unmap"}: curl block device does not support writes
We obviously can encode that knowledge into libvirt but it will be hard to undo if qemu eventually supports writes in the curl driver.
Which other protocol drivers don't support writes? in case we have to go this way.
Quoted 5 lines · Peter Krempa
block-commit is able to reopen the format layers and works as expected.
Unfortunately though the 'read-only' option is actually useful as the curl-driver does not work without it:
Quoted 7 lines
-blockdev {"driver":"http","url":"http://ftp.sjtu.edu.cn:80/ubuntu-cd/12.04/ubuntu-12.04.5-alternate-amd64.iso","node-name":"libvirt-2-storage","discard":"unmap"}: curl block device does not support writes
We obviously can encode that knowledge into libvirt but it will be hard to undo if qemu eventually supports writes in the curl driver.
Which other protocol drivers don't support writes? in case we have to go this way.
When an NBD server exported an image as read-only, the NBD block client cannot request write permissions. But that's a runtime discovery process, not a limitation of the block driver itself.
Signature · 3 lines
Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
Quoted 12 lines · Eric Blake
Quoted 10 lines · Peter Krempa
block-commit is able to reopen the format layers and works as expected.
Unfortunately though the 'read-only' option is actually useful as the curl-driver does not work without it:
-blockdev {"driver":"http","url":"http://ftp.sjtu.edu.cn:80/ubuntu-cd/12.04/ubuntu-12.04.5-alternate-amd64.iso","node-name":"libvirt-2-storage","discard":"unmap"}: curl block device does not support writes
We obviously can encode that knowledge into libvirt but it will be hard to undo if qemu eventually supports writes in the curl driver.
Quoted 6 lines
Quoted 2 lines
Which other protocol drivers don't support writes? in case we have to go this way.
When an NBD server exported an image as read-only, the NBD block client cannot request write permissions. But that's a runtime discovery process, not a limitation of the block driver itself.
Hmmm, that's unfortunate. Because in some cases we don't know this fact upfront in libvirt and we also don't know whether an user might attempt to block-commit at some time.
We probably do need a way to specify that we want
'read-write-if-possible' behaviour.
Peter
Am 05.09.2018 um 16:02 hat Peter Krempa geschrieben:
Quoted 20 lines · Eric Blake
Quoted 12 lines · Peter Krempa
Quoted 11 lines
block-commit is able to reopen the format layers and works as expected.
Unfortunately though the 'read-only' option is actually useful as the curl-driver does not work without it:
-blockdev {"driver":"http","url":"http://ftp.sjtu.edu.cn:80/ubuntu-cd/12.04/ubuntu-12.04.5-alternate-amd64.iso","node-name":"libvirt-2-storage","discard":"unmap"}: curl block device does not support writes
We obviously can encode that knowledge into libvirt but it will be hard to undo if qemu eventually supports writes in the curl driver.
Quoted 6 lines
Quoted 2 lines
Which other protocol drivers don't support writes? in case we have to go this way.
When an NBD server exported an image as read-only, the NBD block client cannot request write permissions. But that's a runtime discovery process, not a limitation of the block driver itself.
Quoted 6 lines
Hmmm, that's unfortunate. Because in some cases we don't know this fact upfront in libvirt and we also don't know whether an user might attempt to block-commit at some time.
We probably do need a way to specify that we want
'read-write-if-possible' behaviour.
So after all, maybe we should try whether a read-only=auto is possible, which would reopen the image file on demand (depending on whether some user of the node requested BLK_PERM_WRITE etc.)
Kevin
Quoted 83 lines · Kevin Wolf
Am 28.08.2018 um 16:26 hat Peter Krempa geschrieben:
Quoted 49 lines · Kevin Wolf
Quoted 9 lines
The block-commit QMP command required specifying the top and base nodes of the commit jobs using the file name of that node. While this works in simple cases (local files with absolute paths), the file names generated for more complicated setups can be hard to predict.
This adds two new options top-node and base-node to the command, which allow specifying node names instead. They are mutually exclusive with the old options.
Quoted 5 lines
Signed-off-by Kevin Wolf <[email protected]>--- qapi/block-core.json | 24 ++++++++++++++++++------ blockdev.c | 32 ++++++++++++++++++++++++++++++-- 2 files changed, 48 insertions(+), 8 deletions(-)While the below is not strictly relevant to this patch usage block-commit is not possible when using -blockdev. Thus the new arguments are not very useful otherwise.
With the new options I'm getting:
{"execute":"block-commit",
"arguments": { "device":"libvirt-3-format","job-id":"libvirt-3-format", "top-node":"libvirt-8-format", "base-node":"libvirt-9-format", "auto-finalize":true, "auto-dismiss":false},"id":"libvirt-16"}
{"id":"libvirt-16",
"error":{"class":"GenericError","desc":"Block node is read-only"}}I'm pointing into the backing chain so the files are declared as read-only.
It works just-fine if I open them as read-write with -blockdev/blockdev-add but that obviously is not correct as you can't then share parts of the backing chain with other VMs due to image locking.
libvirt-3-format is read-write and all other node names are readonly in the above example.
The same also happens when using filenames:
{"execute":"block-commit",
"arguments" : {"device":"libvirt-3-format",Quoted 8 lines
"job-id":"libvirt-3-format", "top":"/var/lib/libvirt/images/rhel7.3.1483615252", "base":"/var/lib/libvirt/images/rhel7.3.1483605924", "auto-finalize":true, "auto-dismiss":false},"id":"libvirt-13"}
{"id":"libvirt-13","error":{"class":"GenericError","desc":"Block node is read-only"}}
I see what's happening here. So we have a graph like this:
guest device | v overlay-format -------> backing-format [read-only=off] [read-only=on] | | v v overlay-proto backing-proto [read-only=off] [read-only=on]The difference between your -blockdev use and -drive is that you explicitly specify the read-only option for backing-proto (and you use a separate -blockdev option anyway), so it doesn't just inherit it from backing-format.
Now, when the commit job tries to reopen backing-format, your explicit read-only=on for backing-proto still takes precedence and the node stays read-only. If you hadn't used a separate -blockdev for backing-proto, but included it in the definition for backing-format and left out the read-only option, it would have inherited the option and reopen would adjust both nodes. This is what happens with -drive.
Quoted 3 lines
So essentially, I guess, all places that want to switch between read-only and read-write need to learn which other nodes (apart from the top-level node they are interested in) must be reopened as well.
We theoretically can always open the protocol layer read-write if it does not conflict with the image locking code (I did not test that).
Changing to opening them as dependancy of the format layer would complicate things with blockdev-create where that would not be possible and would require blockdev-add(proto), blockdev-create, blockdev-del(proto),blockdev-add (format+proto).
PATCH 2/2 qemu-iotests: Test commit with top-node/base-node
In reply to Kevin WolfThis adds some tests for block-commit with the new options top-node and base-node (taking node names) instead of top and base (taking file names).
--- tests/qemu-iotests/040 | 52 ++++++++++++++++++++++++++++++++++++++++++++-- tests/qemu-iotests/040.out | 4 ++-- 2 files changed, 52 insertions(+), 4 deletions(-)
tests/qemu-iotests/040 +50 -2
@@ -57,9 +57,12 @@ class ImageCommitTestCase(iotests.QMPTestCase): self.assert_no_active_block_jobs() self.vm.shutdown() - def run_commit_test(self, top, base, need_ready=False): + def run_commit_test(self, top, base, need_ready=False, node_names=False): self.assert_no_active_block_jobs() - result = self.vm.qmp('block-commit', device='drive0', top=top, base=base) + if node_names: + result = self.vm.qmp('block-commit', device='drive0', top_node=top, base_node=base) + else: + result = self.vm.qmp('block-commit', device='drive0', top=top, base=base) self.assert_qmp(result, 'return', {}) self.wait_for_complete(need_ready)
@@ -101,6 +104,11 @@ class TestSingleDrive(ImageCommitTestCase): self.assertEqual(-1, qemu_io('-f', 'raw', '-c', 'read -P 0xab 0 524288', backing_img).find("verification failed")) self.assertEqual(-1, qemu_io('-f', 'raw', '-c', 'read -P 0xef 524288 524288', backing_img).find("verification failed")) + def test_commit_node(self): + self.run_commit_test("mid", "base", node_names=True) + self.assertEqual(-1, qemu_io('-f', 'raw', '-c', 'read -P 0xab 0 524288', backing_img).find("verification failed")) + self.assertEqual(-1, qemu_io('-f', 'raw', '-c', 'read -P 0xef 524288 524288', backing_img).find("verification failed")) + def test_device_not_found(self): result = self.vm.qmp('block-commit', device='nonexistent', top='%s' % mid_img) self.assert_qmp(result, 'error/class', 'DeviceNotFound')
@@ -123,6 +131,30 @@ class TestSingleDrive(ImageCommitTestCase): self.assert_qmp(result, 'error/class', 'GenericError') self.assert_qmp(result, 'error/desc', 'Base \'badfile\' not found') + def test_top_node_invalid(self): + self.assert_no_active_block_jobs() + result = self.vm.qmp('block-commit', device='drive0', top_node='badfile', base_node='base') + self.assert_qmp(result, 'error/class', 'GenericError') + self.assert_qmp(result, 'error/desc', "Cannot find device= nor node_name=badfile") + + def test_base_node_invalid(self): + self.assert_no_active_block_jobs() + result = self.vm.qmp('block-commit', device='drive0', top_node='mid', base_node='badfile') + self.assert_qmp(result, 'error/class', 'GenericError') + self.assert_qmp(result, 'error/desc', "Cannot find device= nor node_name=badfile") + + def test_top_path_and_node(self): + self.assert_no_active_block_jobs() + result = self.vm.qmp('block-commit', device='drive0', top_node='mid', base_node='base', top='%s' % mid_img) + self.assert_qmp(result, 'error/class', 'GenericError') + self.assert_qmp(result, 'error/desc', "'top-node' and 'top' are mutually exclusive") + + def test_base_path_and_node(self): + self.assert_no_active_block_jobs() + result = self.vm.qmp('block-commit', device='drive0', top_node='mid', base_node='base', base='%s' % backing_img) + self.assert_qmp(result, 'error/class', 'GenericError') + self.assert_qmp(result, 'error/desc', "'base-node' and 'base' are mutually exclusive") + def test_top_is_active(self): self.run_commit_test(test_img, backing_img, need_ready=True) self.assertEqual(-1, qemu_io('-f', 'raw', '-c', 'read -P 0xab 0 524288', backing_img).find("verification failed"))
@@ -139,6 +171,22 @@ class TestSingleDrive(ImageCommitTestCase): self.assert_qmp(result, 'error/class', 'GenericError') self.assert_qmp(result, 'error/desc', 'Base \'%s\' not found' % mid_img) + def test_top_and_base_node_reversed(self): + self.assert_no_active_block_jobs() + result = self.vm.qmp('block-commit', device='drive0', top_node='base', base_node='top') + self.assert_qmp(result, 'error/class', 'GenericError') + self.assert_qmp(result, 'error/desc', "'top' is not in this backing file chain") + + def test_top_node_in_wrong_chain(self): + self.assert_no_active_block_jobs() + + result = self.vm.qmp('blockdev-add', driver='null-co', node_name='null') + self.assert_qmp(result, 'return', {}) + + result = self.vm.qmp('block-commit', device='drive0', top_node='null', base_node='base') + self.assert_qmp(result, 'error/class', 'GenericError') + self.assert_qmp(result, 'error/desc', "'null' is not in this backing file chain") + # When the job is running on a BB that is automatically deleted on hot # unplug, the job is cancelled when the device disappears def test_hot_unplug(self):
tests/qemu-iotests/040.out +2 -2
@@ -1,5 +1,5 @@ -............................. +........................................... ---------------------------------------------------------------------- -Ran 29 tests +Ran 43 tests OK
Signature · 1 line
2.13.6
Re: [Qemu-devel] [PATCH 2/2] qemu-iotests: Test commit with top-node/base-node
Quoted 3 lines · Kevin Wolf
This adds some tests for block-commit with the new options top-node and base-node (taking node names) instead of top and base (taking file names).
May need a rewrite if you like my idea of "by-node":true.
Quoted 12 lines
Signed-off-by Kevin Wolf <[email protected]>--- tests/qemu-iotests/040 | 52 ++++++++++++++++++++++++++++++++++++++++++++-- tests/qemu-iotests/040.out | 4 ++-- 2 files changed, 52 insertions(+), 4 deletions(-)tests/qemu-iotests/040 +0
-0
tests/qemu-iotests/040 class ImageCommitTestCase(iotests.QMPTestCase): · line 60
Quoted 5 lines
tests/qemu-iotests/040 +1
-1@@ -57,9 +57,12 @@ class ImageCommitTestCase(iotests.QMPTestCase): self.assert_no_active_block_jobs() self.vm.shutdown() - def run_commit_test(self, top, base, need_ready=False): + def run_commit_test(self, top, base, need_ready=False, node_names=False):
Especially since you've already picked that style of signature here :)
Signature · 3 lines
Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
Am 10.08.2018 um 18:26 hat Kevin Wolf geschrieben:
Quoted 3 lines
Kevin Wolf (2):
commit: Add top-node/base-node options
qemu-iotests: Test commit with top-node/base-node
Fixed the version numbers in the QMP documentation and applied to the block branch.
I'll still have to look into Peter's problem, but as the same happens with filenames, there's no reason why it should hold up this series.
Kevin