From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35481) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZtwId-0004Tb-04 for qemu-devel@nongnu.org; Wed, 04 Nov 2015 06:32:22 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZtwIW-0004qx-Tf for qemu-devel@nongnu.org; Wed, 04 Nov 2015 06:32:18 -0500 Received: from mailhub.sw.ru ([195.214.232.25]:4456 helo=relay.sw.ru) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZtwIQ-0004nu-Fp for qemu-devel@nongnu.org; Wed, 04 Nov 2015 06:32:12 -0500 From: "Denis V. Lunev" Date: Wed, 4 Nov 2015 14:31:55 +0300 Message-Id: <1446636716-9721-1-git-send-email-den@openvz.org> In-Reply-To: <87ziyuksbw.fsf@emacs.mitica> References: <87ziyuksbw.fsf@emacs.mitica> Subject: [Qemu-devel] [PATCH RFC 1/2] snapshot: create helper to test that block drivers supports snapshots List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Denis V. Lunev" , qemu-devel@nongnu.org, Stefan Hajnoczi , Juan Quintela 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" 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) +{ + 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); + 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(); -- 2.5.0