From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37360) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZtZKA-0004OF-PG for qemu-devel@nongnu.org; Tue, 03 Nov 2015 06:00:23 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZtZK6-0002iJ-PX for qemu-devel@nongnu.org; Tue, 03 Nov 2015 06:00:22 -0500 From: Wen Congyang Date: Tue, 3 Nov 2015 18:58:40 +0800 Message-ID: <1446548329-17475-4-git-send-email-wency@cn.fujitsu.com> In-Reply-To: <1446548329-17475-1-git-send-email-wency@cn.fujitsu.com> References: <1446548329-17475-1-git-send-email-wency@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain Subject: [Qemu-devel] [PATCH v11 03/12] allow writing to the backing file List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu devel , Fam Zheng , Max Reitz , Paolo Bonzini , Stefan Hajnoczi Cc: Kevin Wolf , qemu block , Jiang Yunhong , Dong Eddie , "Dr. David Alan Gilbert" , "Michael R. Hines" , Gonglei , zhanghailiang For block replication, we have such backing chain: secondary disk <-- hidden disk <-- active disk secondary disk is top BDS (use bacing reference), so it can be opened in read-write mode. But hidden disk is read only, and we need to write to hidden disk (backup job will write data to it). TODO: support opening backing file in read-write mode if the BDS is created by QMP command blockdev-add. Signed-off-by: Wen Congyang Signed-off-by: zhanghailiang Signed-off-by: Gonglei --- block.c | 41 ++++++++++++++++++++++++++++++++++++++++- 1 file changed, 40 insertions(+), 1 deletion(-) diff --git a/block.c b/block.c index 52a91ad..32ed776 100644 --- a/block.c +++ b/block.c @@ -737,6 +737,15 @@ static const BdrvChildRole child_backing = { .inherit_flags = bdrv_backing_flags, }; +static int bdrv_backing_rw_flags(int flags) +{ + return bdrv_backing_flags(flags) | BDRV_O_RDWR; +} + +static const BdrvChildRole child_backing_rw = { + .inherit_flags = bdrv_backing_rw_flags, +}; + static int bdrv_open_flags(BlockDriverState *bs, int flags) { int open_flags = flags | BDRV_O_CACHE_WB; @@ -1184,6 +1193,20 @@ out: bdrv_refresh_limits(bs, NULL); } +#define ALLOW_WRITE_BACKING_FILE "allow-write-backing-file" +static QemuOptsList backing_file_opts = { + .name = "backing_file", + .head = QTAILQ_HEAD_INITIALIZER(backing_file_opts.head), + .desc = { + { + .name = ALLOW_WRITE_BACKING_FILE, + .type = QEMU_OPT_BOOL, + .help = "allow writes to backing file", + }, + { /* end of list */ } + }, +}; + /* * Opens the backing file for a BlockDriverState if not yet open * @@ -1198,6 +1221,9 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp) int ret = 0; BlockDriverState *backing_hd; Error *local_err = NULL; + QemuOpts *opts = NULL; + bool child_rw = false; + const BdrvChildRole *child_role = NULL; if (bs->backing != NULL) { QDECREF(options); @@ -1210,6 +1236,18 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp) } bs->open_flags &= ~BDRV_O_NO_BACKING; + + opts = qemu_opts_create(&backing_file_opts, NULL, 0, &error_abort); + qemu_opts_absorb_qdict(opts, options, &local_err); + if (local_err) { + ret = -EINVAL; + error_propagate(errp, local_err); + QDECREF(options); + goto free_exit; + } + child_rw = qemu_opt_get_bool(opts, ALLOW_WRITE_BACKING_FILE, false); + child_role = child_rw ? &child_backing_rw : &child_backing; + if (qdict_haskey(options, "file.filename")) { backing_filename[0] = '\0'; } else if (bs->backing_file[0] == '\0' && qdict_size(options) == 0) { @@ -1242,7 +1280,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp) assert(bs->backing == NULL); ret = bdrv_open_inherit(&backing_hd, *backing_filename ? backing_filename : NULL, - NULL, options, 0, bs, &child_backing, &local_err); + NULL, options, 0, bs, child_role, &local_err); if (ret < 0) { bdrv_unref(backing_hd); backing_hd = NULL; @@ -1259,6 +1297,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp) bdrv_unref(backing_hd); free_exit: + qemu_opts_del(opts); g_free(backing_filename); return ret; } -- 2.4.3