From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46943) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ztwr2-0000A8-Im for qemu-devel@nongnu.org; Wed, 04 Nov 2015 07:07:53 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Ztwqx-000686-Kd for qemu-devel@nongnu.org; Wed, 04 Nov 2015 07:07:52 -0500 Received: from mx1.redhat.com ([209.132.183.28]:39400) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ztwqx-00067y-1R for qemu-devel@nongnu.org; Wed, 04 Nov 2015 07:07:47 -0500 From: Juan Quintela In-Reply-To: <1446636716-9721-1-git-send-email-den@openvz.org> (Denis V. Lunev's message of "Wed, 4 Nov 2015 14:31:55 +0300") References: <87ziyuksbw.fsf@emacs.mitica> <1446636716-9721-1-git-send-email-den@openvz.org> Date: Wed, 04 Nov 2015 13:07:44 +0100 Message-ID: <87io5ic6i7.fsf@emacs.mitica> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH RFC 1/2] snapshot: create helper to test that block drivers supports snapshots Reply-To: quintela@redhat.com List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Denis V. Lunev" Cc: qemu-devel@nongnu.org, Stefan Hajnoczi "Denis V. Lunev" wrote: > The patch enforces proper locking for this operation. > > Signed-off-by: Denis V. Lunev > CC: Stefan Hajnoczi > CC: Juan Quintela > --- > Patches are compile-tested only. Sent to check the approach, naming and > functions placement. Functions are returning bad BlockDriver via > parameter to make clear distinction when I'll have to return BS to write. > > block/snapshot.c | 35 +++++++++++++++++++++++++++++++++++ > include/block/snapshot.h | 9 +++++++++ > migration/savevm.c | 17 ++++------------- > 3 files changed, 48 insertions(+), 13 deletions(-) > > diff --git a/block/snapshot.c b/block/snapshot.c > index 89500f2..6b5ce4e 100644 > --- a/block/snapshot.c > +++ b/block/snapshot.c > @@ -25,6 +25,7 @@ > #include "block/snapshot.h" > #include "block/block_int.h" > #include "qapi/qmp/qerror.h" > +#include "monitor/monitor.h" You don't need the monitor here O:-) > > QemuOptsList internal_snapshot_opts = { > .name = "snapshot", > @@ -356,3 +357,37 @@ int bdrv_snapshot_load_tmp_by_id_or_name(BlockDriverState *bs, > > return ret; > } > + > + > +/* Group operations. All block drivers are involved. > + * These functions will properly handle dataplace (take aio_context_acquire > + * when appropriate for appropriate block drivers > + * > + * Returned block driver will be always locked. > + */ > + > +bool bdrv_snapshot_all_can_snapshot(BlockDriverState **first_bad_bs) bdrv_snapshot_is_possible??? > +{ > + BlockDriverState *bs; > + > + while ((bs = bdrv_next(bs))) { > + bool ok; > + AioContext *ctx = bdrv_get_aio_context(bs); > + > + if (!bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) { > + continue; > + } > + > + aio_context_acquire(ctx); I think that you should get the lock before the bdrv_is_inserted, but who am I to know for sure O:-) > + ok = bdrv_can_snapshot(bs); > + aio_context_release(ctx); > + > + if (!ok) { > + *first_bad_bs = bs; > + return false; > + } > + } > + > + *first_bad_bs = NULL; > + return true; > +} > diff --git a/include/block/snapshot.h b/include/block/snapshot.h > index 770d9bb..61b4b5d 100644 > --- a/include/block/snapshot.h > +++ b/include/block/snapshot.h > @@ -75,4 +75,13 @@ int bdrv_snapshot_load_tmp(BlockDriverState *bs, > int bdrv_snapshot_load_tmp_by_id_or_name(BlockDriverState *bs, > const char *id_or_name, > Error **errp); > + > + > +/* Group operations. All block drivers are involved. > + * These functions will properly handle dataplace (take aio_context_acquire > + * when appropriate for appropriate block drivers > + * > + */ > +bool bdrv_snapshot_all_can_snapshot(BlockDriverState **first_bad_bs); > + > #endif > diff --git a/migration/savevm.c b/migration/savevm.c > index dbcc39a..91ba0bf 100644 > --- a/migration/savevm.c > +++ b/migration/savevm.c > @@ -1290,19 +1290,10 @@ void hmp_savevm(Monitor *mon, const QDict *qdict) > const char *name = qdict_get_try_str(qdict, "name"); > Error *local_err = NULL; > > - /* Verify if there is a device that doesn't support snapshots and is writable */ > - bs = NULL; > - while ((bs = bdrv_next(bs))) { > - > - if (!bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) { > - continue; > - } > - > - if (!bdrv_can_snapshot(bs)) { > - monitor_printf(mon, "Device '%s' is writable but does not support snapshots.\n", > - bdrv_get_device_name(bs)); > - return; > - } > + if (bdrv_snapshot_all_can_snapshot(&bs)) { > + monitor_printf(mon, "Device '%s' is writable but does not " > + "support snapshots.\n", bdrv_get_device_name(bs)); > + return; > } > > bs = find_vmstate_bs(); ok with the savevm.c changes.