| Message ID | 20200625152215.941773-30-mreitz@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | block: Deal with filters | expand |
On 25.06.2020 18:21, Max Reitz wrote: > This allows us to differentiate between filters and nodes with COW > backing files: Filters cannot be used as overlays at all (for this > function). > > Signed-off-by: Max Reitz <mreitz@redhat.com> > --- > blockdev.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/blockdev.c b/blockdev.c > index 1eb0fcdea2..aabe51036d 100644 > --- a/blockdev.c > +++ b/blockdev.c > @@ -1549,7 +1549,12 @@ static void external_snapshot_prepare(BlkActionState *common, > goto out; > } > > - if (state->new_bs->backing != NULL) { > + if (state->new_bs->drv->is_filter) { Is there a chance to get a filter here? If so, is that when a user specifies the file name of such a kind “filter[filter-name]:foo.qcow2” or somehow else? Andrey > + error_setg(errp, "Filters cannot be used as overlays"); > + goto out; > + } > + > + if (bdrv_cow_child(state->new_bs)) { > error_setg(errp, "The overlay already has a backing image"); > goto out; > } Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
On 20.07.20 18:08, Andrey Shinkevich wrote: > On 25.06.2020 18:21, Max Reitz wrote: >> This allows us to differentiate between filters and nodes with COW >> backing files: Filters cannot be used as overlays at all (for this >> function). >> >> Signed-off-by: Max Reitz <mreitz@redhat.com> >> --- >> blockdev.c | 7 ++++++- >> 1 file changed, 6 insertions(+), 1 deletion(-) >> >> diff --git a/blockdev.c b/blockdev.c >> index 1eb0fcdea2..aabe51036d 100644 >> --- a/blockdev.c >> +++ b/blockdev.c >> @@ -1549,7 +1549,12 @@ static void >> external_snapshot_prepare(BlkActionState *common, >> goto out; >> } >> - if (state->new_bs->backing != NULL) { >> + if (state->new_bs->drv->is_filter) { > > > Is there a chance to get a filter here? If so, is that when a user > specifies the file name of such a kind “filter[filter-name]:foo.qcow2” > or somehow else? It would be with blockdev-snapshot and by specifying a filter for @overlay. Technically that’s already caught by the check whether the overlay supports backing images (whether drv->supports_backing is true), but we might as well give a nicer error message. Example: {"execute":"qmp_capabilities"} {"execute":"blockdev-add","arguments": {"node-name":"overlay","driver":"copy-on-read", "file":{"driver":"null-co"}}} {"execute":"blockdev-add","arguments": {"node-name":"base","driver":"null-co"}} {"execute":"blockdev-snapshot","arguments": {"node":"base","overlay":"overlay"}} Max
On 24.07.2020 12:23, Max Reitz wrote: > On 20.07.20 18:08, Andrey Shinkevich wrote: >> On 25.06.2020 18:21, Max Reitz wrote: >>> This allows us to differentiate between filters and nodes with COW >>> backing files: Filters cannot be used as overlays at all (for this >>> function). >>> >>> Signed-off-by: Max Reitz <mreitz@redhat.com> >>> --- >>> blockdev.c | 7 ++++++- >>> 1 file changed, 6 insertions(+), 1 deletion(-) >>> >>> diff --git a/blockdev.c b/blockdev.c >>> index 1eb0fcdea2..aabe51036d 100644 >>> --- a/blockdev.c >>> +++ b/blockdev.c >>> @@ -1549,7 +1549,12 @@ static void >>> external_snapshot_prepare(BlkActionState *common, >>> goto out; >>> } >>> - if (state->new_bs->backing != NULL) { >>> + if (state->new_bs->drv->is_filter) { >> >> Is there a chance to get a filter here? If so, is that when a user >> specifies the file name of such a kind “filter[filter-name]:foo.qcow2” >> or somehow else? > It would be with blockdev-snapshot and by specifying a filter for > @overlay. Technically that’s already caught by the check whether the > overlay supports backing images (whether drv->supports_backing is true), > but we might as well give a nicer error message. > > Example: > > {"execute":"qmp_capabilities"} > > {"execute":"blockdev-add","arguments": > {"node-name":"overlay","driver":"copy-on-read", > "file":{"driver":"null-co"}}} > > {"execute":"blockdev-add","arguments": > {"node-name":"base","driver":"null-co"}} > > {"execute":"blockdev-snapshot","arguments": > {"node":"base","overlay":"overlay"}} > > Max > Thank you for the example. Andrey
diff --git a/blockdev.c b/blockdev.c index 1eb0fcdea2..aabe51036d 100644 --- a/blockdev.c +++ b/blockdev.c @@ -1549,7 +1549,12 @@ static void external_snapshot_prepare(BlkActionState *common, goto out; } - if (state->new_bs->backing != NULL) { + if (state->new_bs->drv->is_filter) { + error_setg(errp, "Filters cannot be used as overlays"); + goto out; + } + + if (bdrv_cow_child(state->new_bs)) { error_setg(errp, "The overlay already has a backing image"); goto out; }
This allows us to differentiate between filters and nodes with COW backing files: Filters cannot be used as overlays at all (for this function). Signed-off-by: Max Reitz <mreitz@redhat.com> --- blockdev.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)