| Message ID | 20190131143151.6146-1-kwolf@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | block: Fix invalidate_cache error path for parent activation | expand |
On Thu, Jan 31, 2019 at 03:31:51PM +0100, Kevin Wolf wrote: > bdrv_co_invalidate_cache() clears the BDRV_O_INACTIVE flag before > actually activating a node so that the correct permissions etc. are > taken. In case of errors, the flag must be restored so that the next > call to bdrv_co_invalidate_cache() retries activation. > > Restoring the flag was missing in the error path for a failed > parent->role->activate() call. The consequence is that this attempt to > activate all images correctly fails because we still set errp, however > on the next attempt BDRV_O_INACTIVE is already clear, so we return > success without actually retrying the failed action. > > An example where this is observable in practice is migration to a QEMU > instance that has a raw format block node attached to a guest device > with share-rw=off (the default) while another process holds > BLK_PERM_WRITE for the same image. In this case, all activation steps > before parent->role->activate() succeed because raw can tolerate other > writers to the image. Only the parent callback (in particular > blk_root_activate()) tries to implement the share-rw=on property and > requests exclusive write permissions. This fails when the migration > completes and correctly displays an error. However, a manual 'cont' will > incorrectly resume the VM without calling blk_root_activate() again. > > This case is described in more detail in the following bug report: > https://bugzilla.redhat.com/show_bug.cgi?id=1531888 > > Fix this by correctly restoring the BDRV_O_INACTIVE flag in the error > path. > > Cc: qemu-stable@nongnu.org > Signed-off-by: Kevin Wolf <kwolf@redhat.com> > --- > block.c | 1 + > 1 file changed, 1 insertion(+) Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Kevin Wolf <kwolf@redhat.com> writes: > bdrv_co_invalidate_cache() clears the BDRV_O_INACTIVE flag before > actually activating a node so that the correct permissions etc. are > taken. In case of errors, the flag must be restored so that the next > call to bdrv_co_invalidate_cache() retries activation. > > Restoring the flag was missing in the error path for a failed > parent->role->activate() call. The consequence is that this attempt to > activate all images correctly fails because we still set errp, however > on the next attempt BDRV_O_INACTIVE is already clear, so we return > success without actually retrying the failed action. > > An example where this is observable in practice is migration to a QEMU > instance that has a raw format block node attached to a guest device > with share-rw=off (the default) while another process holds > BLK_PERM_WRITE for the same image. In this case, all activation steps > before parent->role->activate() succeed because raw can tolerate other > writers to the image. Only the parent callback (in particular > blk_root_activate()) tries to implement the share-rw=on property and > requests exclusive write permissions. This fails when the migration > completes and correctly displays an error. However, a manual 'cont' will > incorrectly resume the VM without calling blk_root_activate() again. > > This case is described in more detail in the following bug report: > https://bugzilla.redhat.com/show_bug.cgi?id=1531888 > > Fix this by correctly restoring the BDRV_O_INACTIVE flag in the error > path. > > Cc: qemu-stable@nongnu.org > Signed-off-by: Kevin Wolf <kwolf@redhat.com> > --- > block.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/block.c b/block.c > index 0eba8ebe5c..7f5c9bb02b 100644 > --- a/block.c > +++ b/block.c > @@ -4549,6 +4549,7 @@ static void coroutine_fn bdrv_co_invalidate_cache(BlockDriverState *bs, > if (parent->role->activate) { > parent->role->activate(parent, &local_err); > if (local_err) { > + bs->open_flags |= BDRV_O_INACTIVE; > error_propagate(errp, local_err); > return; > } Tested-by: Markus Armbruster <armbru@redhat.com>
diff --git a/block.c b/block.c index 0eba8ebe5c..7f5c9bb02b 100644 --- a/block.c +++ b/block.c @@ -4549,6 +4549,7 @@ static void coroutine_fn bdrv_co_invalidate_cache(BlockDriverState *bs, if (parent->role->activate) { parent->role->activate(parent, &local_err); if (local_err) { + bs->open_flags |= BDRV_O_INACTIVE; error_propagate(errp, local_err); return; }
bdrv_co_invalidate_cache() clears the BDRV_O_INACTIVE flag before actually activating a node so that the correct permissions etc. are taken. In case of errors, the flag must be restored so that the next call to bdrv_co_invalidate_cache() retries activation. Restoring the flag was missing in the error path for a failed parent->role->activate() call. The consequence is that this attempt to activate all images correctly fails because we still set errp, however on the next attempt BDRV_O_INACTIVE is already clear, so we return success without actually retrying the failed action. An example where this is observable in practice is migration to a QEMU instance that has a raw format block node attached to a guest device with share-rw=off (the default) while another process holds BLK_PERM_WRITE for the same image. In this case, all activation steps before parent->role->activate() succeed because raw can tolerate other writers to the image. Only the parent callback (in particular blk_root_activate()) tries to implement the share-rw=on property and requests exclusive write permissions. This fails when the migration completes and correctly displays an error. However, a manual 'cont' will incorrectly resume the VM without calling blk_root_activate() again. This case is described in more detail in the following bug report: https://bugzilla.redhat.com/show_bug.cgi?id=1531888 Fix this by correctly restoring the BDRV_O_INACTIVE flag in the error path. Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf <kwolf@redhat.com> --- block.c | 1 + 1 file changed, 1 insertion(+)