| Message ID | 1443161858-20533-2-git-send-email-wency@cn.fujitsu.com |
|---|---|
| State | New |
| Headers | show |
On 09/25/2015 12:17 AM, Wen Congyang wrote: > For block replication, we have such backing chain: > secondary disk <-- hidden disk <-- active disk > secondary disk is top BDS(use bacing reference), so it can be opened in s/BDS(use bacing/BDS (use backing/ > read-write mode. But hidden disk is read only, and we need to write to > hidden disk(backup job will write data to it). s/disk(/disk (/ > > TODO: support opening backing file in read-write mode if the BDS is > created by QMP command blockdev-add. > > Signed-off-by: Wen Congyang <wency@cn.fujitsu.com> > Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com> > Signed-off-by: Gonglei <arei.gonglei@huawei.com> > --- > block.c | 41 ++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 40 insertions(+), 1 deletion(-) > I really don't like this patch. We are able to automatically (re-)open backing files for write during block-commit, without having to expose a knob to the user then, so exposing a knob to the user here feels wrong. > +#define ALLOW_WRITE_BACKING_FILE "allow-write-backing-file" > +static QemuOptsList backing_file_opts = { > + .name = "backing_file", > + .head = QTAILQ_HEAD_INITIALIZER(backing_file_opts.head), > + .desc = { > + { > + .name = ALLOW_WRITE_BACKING_FILE, > + .type = QEMU_OPT_BOOL, > + .help = "allow writes to backing file", > + }, And even if we DO need this knob (which I doubt), you need corresponding documentation of the knob in qapi/block-core.json, since we are trying to keep the command line and QMP in sync when it comes to adding new options.
On 10/10/2015 03:07 AM, Eric Blake wrote: > On 09/25/2015 12:17 AM, Wen Congyang wrote: >> For block replication, we have such backing chain: >> secondary disk <-- hidden disk <-- active disk >> secondary disk is top BDS(use bacing reference), so it can be opened in > > s/BDS(use bacing/BDS (use backing/ > >> read-write mode. But hidden disk is read only, and we need to write to >> hidden disk(backup job will write data to it). > > s/disk(/disk (/ > >> >> TODO: support opening backing file in read-write mode if the BDS is >> created by QMP command blockdev-add. >> >> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com> >> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com> >> Signed-off-by: Gonglei <arei.gonglei@huawei.com> >> --- >> block.c | 41 ++++++++++++++++++++++++++++++++++++++++- >> 1 file changed, 40 insertions(+), 1 deletion(-) >> > > I really don't like this patch. We are able to automatically (re-)open > backing files for write during block-commit, without having to expose a > knob to the user then, so exposing a knob to the user here feels wrong. I try to reopen the backing files for write when starting block replication. I tested it, and it doesn't work. Here is my usage: command line: -drive if=none,id=colo-disk1,file.filename=/data/images/kvm/suse/temp.img,driver=raw -drive if=virtio,id=active-disk1,driver=replication,mode=secondary,file.driver=qcow2,file.file.filename=/mnt/ramfs/active_disk.img,file.backing.driver=qcow2,file.backing.file.filename=/mnt/ramfs/hidden_disk.img,file.backing.backing.file.filename=/data/images/kvm/suse/suse11_3.img,file.backing.backing.driver=raw,file.backing.backing.node-name=sdisk {'execute': 'blockdev-remove-medium', 'arguments': {'device': 'colo-disk1'} } {'execute': 'blockdev-insert-medium', 'arguments': {'device': 'colo-disk1', 'node-name': 'sdisk'} } {'execute': 'nbd-server-start', 'arguments': {'addr': {'type': 'inet', 'data': {'host': '192.168.3.1', 'port': '8889'} } } } {'execute': 'nbd-server-add', 'arguments': {'device': 'colo-disk1', 'writable': true } } All qmp command success, but the disk exported to nbd server is readonly even if I specify 'writable': true in the QMP commad. The reason is that the BDS is readonly. > >> +#define ALLOW_WRITE_BACKING_FILE "allow-write-backing-file" >> +static QemuOptsList backing_file_opts = { >> + .name = "backing_file", >> + .head = QTAILQ_HEAD_INITIALIZER(backing_file_opts.head), >> + .desc = { >> + { >> + .name = ALLOW_WRITE_BACKING_FILE, >> + .type = QEMU_OPT_BOOL, >> + .help = "allow writes to backing file", >> + }, > > And even if we DO need this knob (which I doubt), you need corresponding > documentation of the knob in qapi/block-core.json, since we are trying > to keep the command line and QMP in sync when it comes to adding new > options. > Yes, I know it, but I don't know how to do it. Update BlockdevOptions? Thanks Wen Congyang
diff --git a/block.c b/block.c index 073d8d6..328c52f 100644 --- a/block.c +++ b/block.c @@ -738,6 +738,15 @@ static const BdrvChildRole child_backing = { .inherit_flags = bdrv_backing_flags, }; +static int bdrv_backing_rw_flags(int flags) +{ + return bdrv_backing_flags(flags) | BDRV_O_RDWR; +} + +static const BdrvChildRole child_backing_rw = { + .inherit_flags = bdrv_backing_rw_flags, +}; + static int bdrv_open_flags(BlockDriverState *bs, int flags) { int open_flags = flags | BDRV_O_CACHE_WB; @@ -1150,6 +1159,20 @@ out: bdrv_refresh_limits(bs, NULL); } +#define ALLOW_WRITE_BACKING_FILE "allow-write-backing-file" +static QemuOptsList backing_file_opts = { + .name = "backing_file", + .head = QTAILQ_HEAD_INITIALIZER(backing_file_opts.head), + .desc = { + { + .name = ALLOW_WRITE_BACKING_FILE, + .type = QEMU_OPT_BOOL, + .help = "allow writes to backing file", + }, + { /* end of list */ } + }, +}; + /* * Opens the backing file for a BlockDriverState if not yet open * @@ -1164,6 +1187,9 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp) int ret = 0; BlockDriverState *backing_hd; Error *local_err = NULL; + QemuOpts *opts = NULL; + bool child_rw = false; + const BdrvChildRole *child_role = NULL; if (bs->backing_hd != NULL) { QDECREF(options); @@ -1176,6 +1202,18 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp) } bs->open_flags &= ~BDRV_O_NO_BACKING; + + opts = qemu_opts_create(&backing_file_opts, NULL, 0, &error_abort); + qemu_opts_absorb_qdict(opts, options, &local_err); + if (local_err) { + ret = -EINVAL; + error_propagate(errp, local_err); + QDECREF(options); + goto free_exit; + } + child_rw = qemu_opt_get_bool(opts, ALLOW_WRITE_BACKING_FILE, false); + child_role = child_rw ? &child_backing_rw : &child_backing; + if (qdict_haskey(options, "file.filename")) { backing_filename[0] = '\0'; } else if (bs->backing_file[0] == '\0' && qdict_size(options) == 0) { @@ -1208,7 +1246,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp) assert(bs->backing_hd == NULL); ret = bdrv_open_inherit(&backing_hd, *backing_filename ? backing_filename : NULL, - NULL, options, 0, bs, &child_backing, &local_err); + NULL, options, 0, bs, child_role, &local_err); if (ret < 0) { bdrv_unref(backing_hd); backing_hd = NULL; @@ -1222,6 +1260,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp) bdrv_set_backing_hd(bs, backing_hd); free_exit: + qemu_opts_del(opts); g_free(backing_filename); return ret; }
For block replication, we have such backing chain: secondary disk <-- hidden disk <-- active disk secondary disk is top BDS(use bacing reference), so it can be opened in read-write mode. But hidden disk is read only, and we need to write to hidden disk(backup job will write data to it). TODO: support opening backing file in read-write mode if the BDS is created by QMP command blockdev-add. Signed-off-by: Wen Congyang <wency@cn.fujitsu.com> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com> Signed-off-by: Gonglei <arei.gonglei@huawei.com> --- block.c | 41 ++++++++++++++++++++++++++++++++++++++++- 1 file changed, 40 insertions(+), 1 deletion(-)