From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50471) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YvJGp-0003Oi-Pn for qemu-devel@nongnu.org; Thu, 21 May 2015 01:43:53 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YvJGk-0007wk-TT for qemu-devel@nongnu.org; Thu, 21 May 2015 01:43:51 -0400 Message-ID: <555D7183.8080203@cn.fujitsu.com> Date: Thu, 21 May 2015 13:47:47 +0800 From: Wen Congyang MIME-Version: 1.0 References: <1431105726-3682-1-git-send-email-kwolf@redhat.com> <1431105726-3682-12-git-send-email-kwolf@redhat.com> In-Reply-To: <1431105726-3682-12-git-send-email-kwolf@redhat.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 11/34] block: Allow references for backing files List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf , qemu-block@nongnu.org Cc: mreitz@redhat.com, qemu-devel@nongnu.org, armbru@redhat.com On 05/09/2015 01:21 AM, Kevin Wolf wrote: > For bs->file, using references to existing BDSes has been possible for a > while already. This patch enables the same for bs->backing_hd. 1. We reference to an existing BDSes, and some disk uses this blk. Do we allow this? 2. bs->backing_hd->blk can be not NULL now? If we do an active commit to this backing file(use mirror job), we will call bdrv_swap() in mirror_exit(), and the function bdrv_swap() doesn't allow that new_bs->blk(here is bs->backing_hd) is not NULL. Thanks Wen Congyang > > Signed-off-by: Kevin Wolf > --- > block.c | 42 ++++++++++++++++++++++++------------------ > block/mirror.c | 2 +- > include/block/block.h | 3 ++- > 3 files changed, 27 insertions(+), 20 deletions(-) > > diff --git a/block.c b/block.c > index e93bf63..95dc51e 100644 > --- a/block.c > +++ b/block.c > @@ -1109,30 +1109,41 @@ out: > /* > * Opens the backing file for a BlockDriverState if not yet open > * > - * options is a QDict of options to pass to the block drivers, or NULL for an > - * empty set of options. The reference to the QDict is transferred to this > - * function (even on failure), so if the caller intends to reuse the dictionary, > - * it needs to use QINCREF() before calling bdrv_file_open. > + * bdrev_key specifies the key for the image's BlockdevRef in the options QDict. > + * That QDict has to be flattened; therefore, if the BlockdevRef is a QDict > + * itself, all options starting with "${bdref_key}." are considered part of the > + * BlockdevRef. > + * > + * TODO Can this be unified with bdrv_open_image()? > */ > -int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp) > +int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options, > + const char *bdref_key, Error **errp) > { > char *backing_filename = g_malloc0(PATH_MAX); > + char *bdref_key_dot; > + const char *reference = NULL; > int ret = 0; > BlockDriverState *backing_hd; > + QDict *options; > Error *local_err = NULL; > > if (bs->backing_hd != NULL) { > - QDECREF(options); > goto free_exit; > } > > /* NULL means an empty set of options */ > - if (options == NULL) { > - options = qdict_new(); > + if (parent_options == NULL) { > + parent_options = qdict_new(); > } > > bs->open_flags &= ~BDRV_O_NO_BACKING; > - if (qdict_haskey(options, "file.filename")) { > + > + bdref_key_dot = g_strdup_printf("%s.", bdref_key); > + qdict_extract_subqdict(parent_options, &options, bdref_key_dot); > + g_free(bdref_key_dot); > + > + reference = qdict_get_try_str(parent_options, bdref_key); > + if (reference || qdict_haskey(options, "file.filename")) { > backing_filename[0] = '\0'; > } else if (bs->backing_file[0] == '\0' && qdict_size(options) == 0) { > QDECREF(options); > @@ -1155,20 +1166,17 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp) > goto free_exit; > } > > - backing_hd = bdrv_new(); > - > if (bs->backing_format[0] != '\0' && !qdict_haskey(options, "driver")) { > qdict_put(options, "driver", qstring_from_str(bs->backing_format)); > } > > assert(bs->backing_hd == NULL); > + backing_hd = NULL; > ret = bdrv_open_inherit(&backing_hd, > *backing_filename ? backing_filename : NULL, > - NULL, options, 0, bs, &child_backing, > + reference, options, 0, bs, &child_backing, > NULL, &local_err); > if (ret < 0) { > - bdrv_unref(backing_hd); > - backing_hd = NULL; > bs->open_flags |= BDRV_O_NO_BACKING; > error_setg(errp, "Could not open backing file: %s", > error_get_pretty(local_err)); > @@ -1176,6 +1184,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp) > goto free_exit; > } > bdrv_set_backing_hd(bs, backing_hd); > + qdict_del(parent_options, bdref_key); > > free_exit: > g_free(backing_filename); > @@ -1463,10 +1472,7 @@ static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename, > > /* If there is a backing file, use it */ > if ((flags & BDRV_O_NO_BACKING) == 0) { > - QDict *backing_options; > - > - qdict_extract_subqdict(options, &backing_options, "backing."); > - ret = bdrv_open_backing_file(bs, backing_options, &local_err); > + ret = bdrv_open_backing_file(bs, options, "backing", &local_err); > if (ret < 0) { > goto close_and_fail; > } > diff --git a/block/mirror.c b/block/mirror.c > index 58f391a..f1bc342 100644 > --- a/block/mirror.c > +++ b/block/mirror.c > @@ -592,7 +592,7 @@ static void mirror_complete(BlockJob *job, Error **errp) > Error *local_err = NULL; > int ret; > > - ret = bdrv_open_backing_file(s->target, NULL, &local_err); > + ret = bdrv_open_backing_file(s->target, NULL, "backing", &local_err); > if (ret < 0) { > error_propagate(errp, local_err); > return; > diff --git a/include/block/block.h b/include/block/block.h > index 27ab2c8..341a551 100644 > --- a/include/block/block.h > +++ b/include/block/block.h > @@ -208,7 +208,8 @@ int bdrv_open_image(BlockDriverState **pbs, const char *filename, > BlockDriverState* parent, const BdrvChildRole *child_role, > bool allow_none, Error **errp); > void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd); > -int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp); > +int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options, > + const char *bdref_key, Error **errp); > int bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, Error **errp); > int bdrv_open(BlockDriverState **pbs, const char *filename, > const char *reference, QDict *options, int flags, >