| Message ID | 1423710438-14377-12-git-send-email-wency@cn.fujitsu.com |
|---|---|
| State | New |
| Headers | show |
On 2015-02-11 at 22:07, Wen Congyang wrote: > 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 | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) I don't think this is a good idea. With this patch, every time you open a COW file (with a backing file) R/W, the backing file will be writable. I'd rather like a way to explicitly overwrite the R/W mode of the backing file; but by default, in my opinion, it should stay read-only. Max > diff --git a/block.c b/block.c > index 067c44b..96cf973 100644 > --- a/block.c > +++ b/block.c > @@ -856,8 +856,8 @@ static int bdrv_inherited_flags(int flags) > */ > static int bdrv_backing_flags(int flags) > { > - /* backing files always opened read-only */ > - flags &= ~(BDRV_O_RDWR | BDRV_O_COPY_ON_READ); > + /* backing files are opened read-write for block replication */ > + flags &= ~BDRV_O_COPY_ON_READ; > > /* snapshot=on is handled on the top layer */ > flags &= ~(BDRV_O_SNAPSHOT | BDRV_O_TEMPORARY);
On 23/02/2015 23:03, Max Reitz wrote: > On 2015-02-11 at 22:07, Wen Congyang wrote: >> 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 | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) > > I don't think this is a good idea. With this patch, every time you open > a COW file (with a backing file) R/W, the backing file will be writable. > I'd rather like a way to explicitly overwrite the R/W mode of the > backing file; but by default, in my opinion, it should stay read-only. I agree. Perhaps blkcolo_open or colo_svm_init can take care of setting BDRV_O_RDWR on the backing file? They could also use bdrv_reopen. Paolo > Max > >> diff --git a/block.c b/block.c >> index 067c44b..96cf973 100644 >> --- a/block.c >> +++ b/block.c >> @@ -856,8 +856,8 @@ static int bdrv_inherited_flags(int flags) >> */ >> static int bdrv_backing_flags(int flags) >> { >> - /* backing files always opened read-only */ >> - flags &= ~(BDRV_O_RDWR | BDRV_O_COPY_ON_READ); >> + /* backing files are opened read-write for block replication */ >> + flags &= ~BDRV_O_COPY_ON_READ; >> /* snapshot=on is handled on the top layer */ >> flags &= ~(BDRV_O_SNAPSHOT | BDRV_O_TEMPORARY); >
diff --git a/block.c b/block.c index 067c44b..96cf973 100644 --- a/block.c +++ b/block.c @@ -856,8 +856,8 @@ static int bdrv_inherited_flags(int flags) */ static int bdrv_backing_flags(int flags) { - /* backing files always opened read-only */ - flags &= ~(BDRV_O_RDWR | BDRV_O_COPY_ON_READ); + /* backing files are opened read-write for block replication */ + flags &= ~BDRV_O_COPY_ON_READ; /* snapshot=on is handled on the top layer */ flags &= ~(BDRV_O_SNAPSHOT | BDRV_O_TEMPORARY);