| Message ID | 1382293700-20192-1-git-send-email-mreitz@redhat.com |
|---|---|
| State | New |
| Headers | show |
On 10/20/2013 07:28 PM, Max Reitz wrote: > Since df2a6f29a5, bdrv_co_do_writev increases the total_sectors value of > a growable block devices on writes after the current end. This leads to > the virtual disk apparently growing in qcow2_save_vmstate, which in turn > affects the disk size captured by the internal snapshot taken directly > afterwards through e.g. the HMP savevm command. Such a "grown" snapshot > cannot be loaded after reopening the qcow2 image, since its disk size > differs from the actual virtual disk size (writing a VM state does not > actually increase the virtual disk size). > > Fix this by restoring total_sectors at the end of qcow2_save_vmstate. > > Signed-off-by: Max Reitz <mreitz@redhat.com> > --- > block/qcow2.c | 5 +++++ > 1 file changed, 5 insertions(+) > > @@ -1946,6 +1947,10 @@ static int qcow2_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, > bs->growable = 1; > ret = bdrv_pwritev(bs, qcow2_vm_state_offset(s) + pos, qiov); > bs->growable = growable; > + // bdrv_co_do_writev will have increased the total_sectors value to include > + // the VM state - the VM state is however not an actual part of the block > + // device, therefore, we need to restore the old value. > + bs->total_sectors = total_sectors; It looks like // comments aren't forbidden, but also uncommon; I don't know if /**/ would be better. At any rate: Reviewed-by: Eric Blake <eblake@redhat.com>
On 2013-10-21 22:36, Eric Blake wrote: > On 10/20/2013 07:28 PM, Max Reitz wrote: >> Since df2a6f29a5, bdrv_co_do_writev increases the total_sectors value of >> a growable block devices on writes after the current end. This leads to >> the virtual disk apparently growing in qcow2_save_vmstate, which in turn >> affects the disk size captured by the internal snapshot taken directly >> afterwards through e.g. the HMP savevm command. Such a "grown" snapshot >> cannot be loaded after reopening the qcow2 image, since its disk size >> differs from the actual virtual disk size (writing a VM state does not >> actually increase the virtual disk size). >> >> Fix this by restoring total_sectors at the end of qcow2_save_vmstate. >> >> Signed-off-by: Max Reitz <mreitz@redhat.com> >> --- >> block/qcow2.c | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> @@ -1946,6 +1947,10 @@ static int qcow2_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, >> bs->growable = 1; >> ret = bdrv_pwritev(bs, qcow2_vm_state_offset(s) + pos, qiov); >> bs->growable = growable; >> + // bdrv_co_do_writev will have increased the total_sectors value to include >> + // the VM state - the VM state is however not an actual part of the block >> + // device, therefore, we need to restore the old value. >> + bs->total_sectors = total_sectors; > It looks like // comments aren't forbidden, but also uncommon; I don't > know if /**/ would be better. At any rate: Ah, right, sorry, I forgot. Max
Am 23.10.2013 um 19:03 hat Max Reitz geschrieben: > On 2013-10-21 22:36, Eric Blake wrote: > >On 10/20/2013 07:28 PM, Max Reitz wrote: > >>Since df2a6f29a5, bdrv_co_do_writev increases the total_sectors value of > >>a growable block devices on writes after the current end. This leads to > >>the virtual disk apparently growing in qcow2_save_vmstate, which in turn > >>affects the disk size captured by the internal snapshot taken directly > >>afterwards through e.g. the HMP savevm command. Such a "grown" snapshot > >>cannot be loaded after reopening the qcow2 image, since its disk size > >>differs from the actual virtual disk size (writing a VM state does not > >>actually increase the virtual disk size). > >> > >>Fix this by restoring total_sectors at the end of qcow2_save_vmstate. > >> > >>Signed-off-by: Max Reitz <mreitz@redhat.com> > >>--- > >> block/qcow2.c | 5 +++++ > >> 1 file changed, 5 insertions(+) > >> > >>@@ -1946,6 +1947,10 @@ static int qcow2_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, > >> bs->growable = 1; > >> ret = bdrv_pwritev(bs, qcow2_vm_state_offset(s) + pos, qiov); > >> bs->growable = growable; > >>+ // bdrv_co_do_writev will have increased the total_sectors value to include > >>+ // the VM state - the VM state is however not an actual part of the block > >>+ // device, therefore, we need to restore the old value. > >>+ bs->total_sectors = total_sectors; > >It looks like // comments aren't forbidden, but also uncommon; I don't > >know if /**/ would be better. At any rate: > > Ah, right, sorry, I forgot. Thanks, fixed up the command and applied to the block branch. Kevin
diff --git a/block/qcow2.c b/block/qcow2.c index c1abaff..5c05bb5 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -1939,6 +1939,7 @@ static int qcow2_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos) { BDRVQcowState *s = bs->opaque; + int64_t total_sectors = bs->total_sectors; int growable = bs->growable; int ret; @@ -1946,6 +1947,10 @@ static int qcow2_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, bs->growable = 1; ret = bdrv_pwritev(bs, qcow2_vm_state_offset(s) + pos, qiov); bs->growable = growable; + // bdrv_co_do_writev will have increased the total_sectors value to include + // the VM state - the VM state is however not an actual part of the block + // device, therefore, we need to restore the old value. + bs->total_sectors = total_sectors; return ret; }
Since df2a6f29a5, bdrv_co_do_writev increases the total_sectors value of a growable block devices on writes after the current end. This leads to the virtual disk apparently growing in qcow2_save_vmstate, which in turn affects the disk size captured by the internal snapshot taken directly afterwards through e.g. the HMP savevm command. Such a "grown" snapshot cannot be loaded after reopening the qcow2 image, since its disk size differs from the actual virtual disk size (writing a VM state does not actually increase the virtual disk size). Fix this by restoring total_sectors at the end of qcow2_save_vmstate. Signed-off-by: Max Reitz <mreitz@redhat.com> --- block/qcow2.c | 5 +++++ 1 file changed, 5 insertions(+)