From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50690) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WmOGo-0004vJ-6M for qemu-devel@nongnu.org; Mon, 19 May 2014 10:10:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WmOGi-0007cp-4T for qemu-devel@nongnu.org; Mon, 19 May 2014 10:10:26 -0400 Received: from oxygen.pond.sub.org ([2a01:4f8:201:233:1::3]:35556) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WmOGh-0007Zi-PP for qemu-devel@nongnu.org; Mon, 19 May 2014 10:10:20 -0400 Received: from blackfin.pond.sub.org (p5B32BA71.dip0.t-ipconnect.de [91.50.186.113]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by oxygen.pond.sub.org (Postfix) with ESMTPSA id D86C1204F4 for ; Mon, 19 May 2014 16:10:17 +0200 (CEST) From: Markus Armbruster References: <1399858555-9672-1-git-send-email-famz@redhat.com> <1399858555-9672-4-git-send-email-famz@redhat.com> Date: Mon, 19 May 2014 16:10:17 +0200 In-Reply-To: <1399858555-9672-4-git-send-email-famz@redhat.com> (Fam Zheng's message of "Mon, 12 May 2014 09:35:42 +0800") Message-ID: <87d2f9q2pi.fsf@blackfin.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH v19 03/16] block: Introduce op_blockers to BlockDriverState List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Fam Zheng Cc: kwolf@redhat.com, jcody@redhat.com, hbrock@redhat.com, qemu-devel@nongnu.org, rjones@redhat.com, imain@redhat.com, stefanha@redhat.com, pbonzini@redhat.com Fam Zheng writes: > BlockDriverState.op_blockers is an array of lists with BLOCK_OP_TYPE_MAX > elements. Each list is a list of blockers of an operation type > (BlockOpType), that marks this BDS as currently blocked for a certain > type of operation with reason errors stored in the list. The rule of > usage is: > > * BDS user who wants to take an operation should check if there's any > blocker of the type with bdrv_op_is_blocked(). > > * BDS user who wants to block certain types of operation, should call > bdrv_op_block (or bdrv_op_block_all to block all types of operations, > which is similar to the existing bdrv_set_in_use()). > > * A blocker is only referenced by op_blockers, so the lifecycle is > managed by caller, and shouldn't be lost until unblock, so typically > a caller does these: > > - Allocate a blocker with error_setg or similar, call bdrv_op_block() > to block some operations. > - Hold the blocker, do his job. > - Unblock operations that it blocked, with the same reason pointer > passed to bdrv_op_unblock(). > - Release the blocker with error_free(). > > Signed-off-by: Fam Zheng > Reviewed-by: Benoit Canet > Reviewed-by: Jeff Cody > --- > block.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++ > include/block/block.h | 7 +++++ > include/block/block_int.h | 5 ++++ > 3 files changed, 87 insertions(+) > > diff --git a/block.c b/block.c > index b749d31..32338ca 100644 > --- a/block.c > +++ b/block.c > @@ -335,6 +335,7 @@ void bdrv_register(BlockDriver *bdrv) > BlockDriverState *bdrv_new(const char *device_name, Error **errp) > { > BlockDriverState *bs; > + int i; > > if (bdrv_find(device_name)) { > error_setg(errp, "Device with id '%s' already exists", > @@ -353,6 +354,9 @@ BlockDriverState *bdrv_new(const char *device_name, Error **errp) > if (device_name[0] != '\0') { > QTAILQ_INSERT_TAIL(&bdrv_states, bs, device_list); > } > + for (i = 0; i < BLOCK_OP_TYPE_MAX; i++) { > + QLIST_INIT(&bs->op_blockers[i]); > + } > bdrv_iostatus_disable(bs); > notifier_list_init(&bs->close_notifiers); > notifier_with_return_list_init(&bs->before_write_notifiers); > @@ -1907,6 +1911,8 @@ static void bdrv_move_feature_fields(BlockDriverState *bs_dest, > pstrcpy(bs_dest->device_name, sizeof(bs_dest->device_name), > bs_src->device_name); > bs_dest->device_list = bs_src->device_list; > + memcpy(bs_dest->op_blockers, bs_src->op_blockers, > + sizeof(bs_dest->op_blockers)); > } > > /* > @@ -5269,6 +5275,75 @@ void bdrv_unref(BlockDriverState *bs) > } > } > > +struct BdrvOpBlocker { > + Error *reason; > + QLIST_ENTRY(BdrvOpBlocker) list; > +}; > + > +bool bdrv_op_is_blocked(BlockDriverState *bs, BlockOpType op, Error **errp) > +{ > + BdrvOpBlocker *blocker; > + assert((int) op >= 0 && op < BLOCK_OP_TYPE_MAX); Space between cast and its operand is unusual. Please don't respin just for that. > + if (!QLIST_EMPTY(&bs->op_blockers[op])) { > + blocker = QLIST_FIRST(&bs->op_blockers[op]); > + if (errp) { > + *errp = error_copy(blocker->reason); > + } > + return true; > + } > + return false; > +} > + > +void bdrv_op_block(BlockDriverState *bs, BlockOpType op, Error *reason) > +{ > + BdrvOpBlocker *blocker; > + assert((int) op >= 0 && op < BLOCK_OP_TYPE_MAX); > + > + blocker = g_malloc0(sizeof(BdrvOpBlocker)); Please consider g_new0(), but don't respin just for that. > + blocker->reason = reason; > + QLIST_INSERT_HEAD(&bs->op_blockers[op], blocker, list); > +} [...]