From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33813) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cvvH9-0001D1-OB for qemu-devel@nongnu.org; Wed, 05 Apr 2017 20:27:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cvvH8-0004OK-Si for qemu-devel@nongnu.org; Wed, 05 Apr 2017 20:27:47 -0400 Date: Wed, 5 Apr 2017 20:27:34 -0400 From: Jeff Cody Message-ID: <20170406002734.GM1135@localhost.localdomain> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH for-2.10 6/9] block: use bdrv_try_set_read_only() during reopen List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: John Snow Cc: qemu-devel@nongnu.org, kwolf@redhat.com, stefanha@redhat.com, qemu-block@nongnu.org On Wed, Apr 05, 2017 at 04:25:39PM -0400, John Snow wrote: > > > On 04/05/2017 02:28 PM, Jeff Cody wrote: > > Signed-off-by: Jeff Cody > > --- > > block.c | 14 ++++++++------ > > 1 file changed, 8 insertions(+), 6 deletions(-) > > > > diff --git a/block.c b/block.c > > index ad958b9..3245fae 100644 > > --- a/block.c > > +++ b/block.c > > @@ -2785,6 +2785,7 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue, > > BlockDriver *drv; > > QemuOpts *opts; > > const char *value; > > + bool read_only; > > > > assert(reopen_state != NULL); > > assert(reopen_state->bs->drv != NULL); > > @@ -2813,12 +2814,13 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue, > > qdict_put(reopen_state->options, "driver", qstring_from_str(value)); > > } > > > > - /* if we are to stay read-only, do not allow permission change > > - * to r/w */ > > - if (!(reopen_state->bs->open_flags & BDRV_O_ALLOW_RDWR) && > > - reopen_state->flags & BDRV_O_RDWR) { > > So the current code checks reopen_state->flags & BDRV_O_RDWR; > > > - error_setg(errp, "Node '%s' is read only", > > - bdrv_get_device_or_node_name(reopen_state->bs)); > > + /* If we are to stay read-only, do not allow permission change > > + * to r/w. Attempting to set to r/w may fail if either BDRV_O_ALLOW_RDWR is > > + * not set, or if the BDS still has copy_on_read enabled */ > > + read_only = !(reopen_state->bs->open_flags & BDRV_O_RDWR); > > And the proposed change checks reopen_state->bs->open_flags & > BDRV_O_RDWR. (It's negated again inside of bdrv_try_set_read_only.) > > Both check against !(reopen_state->bs->open_flags & BDRV_O_ALLOW_RDWR). > > What's the functional difference of doing so, and is it intentional? > Good catch; unintentional. That line should read: + read_only = !(reopen_state->flags & BDRV_O_RDWR); The functional difference is we would be testing against the open_flags of the current BS to see if we are requesting r/w or r/o, rather than checking against the reopen requested flags. > > + ret = bdrv_try_set_read_only(reopen_state->bs, read_only, &local_err); > > + if (local_err) { > > + error_propagate(errp, local_err); > > goto error; > > } > > > >