From: Max Reitz <mreitz@redhat.com>
To: qemu-block@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, Alberto Garcia <berto@igalia.com>,
qemu-devel@nongnu.org, Max Reitz <mreitz@redhat.com>
Subject: [PATCH 10/22] quorum: Implement .bdrv_recurse_can_replace()
Date: Fri, 20 Sep 2019 17:27:52 +0200 [thread overview]
Message-ID: <20190920152804.12875-11-mreitz@redhat.com> (raw)
In-Reply-To: <20190920152804.12875-1-mreitz@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
---
block/quorum.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 62 insertions(+)
diff --git a/block/quorum.c b/block/quorum.c
index 207054a64e..81b57dbae2 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -825,6 +825,67 @@ static bool quorum_recurse_is_first_non_filter(BlockDriverState *bs,
return false;
}
+static bool quorum_recurse_can_replace(BlockDriverState *bs,
+ BlockDriverState *to_replace)
+{
+ BDRVQuorumState *s = bs->opaque;
+ int i;
+
+ for (i = 0; i < s->num_children; i++) {
+ /*
+ * We have no idea whether our children show the same data as
+ * this node (@bs). It is actually highly likely that
+ * @to_replace does not, because replacing a broken child is
+ * one of the main use cases here.
+ *
+ * We do know that the new BDS will match @bs, so replacing
+ * any of our children by it will be safe. It cannot change
+ * the data this quorum node presents to its parents.
+ *
+ * However, replacing @to_replace by @bs in any of our
+ * children's chains may change visible data somewhere in
+ * there. We therefore cannot recurse down those chains with
+ * bdrv_recurse_can_replace().
+ * (More formally, bdrv_recurse_can_replace() requires that
+ * @to_replace will be replaced by something matching the @bs
+ * passed to it. We cannot guarantee that.)
+ *
+ * Thus, we can only check whether any of our immediate
+ * children matches @to_replace.
+ *
+ * (In the future, we might add a function to recurse down a
+ * chain that checks that nothing there cares about a change
+ * in data from the respective child in question. For
+ * example, most filters do not care when their child's data
+ * suddenly changes, as long as their parents do not care.)
+ */
+ if (s->children[i].child->bs == to_replace) {
+ Error *local_err = NULL;
+
+ /*
+ * We now have to ensure that there is no other parent
+ * that cares about replacing this child by a node with
+ * potentially different data.
+ */
+ s->children[i].to_be_replaced = true;
+ bdrv_child_refresh_perms(bs, s->children[i].child, &local_err);
+
+ /* Revert permissions */
+ s->children[i].to_be_replaced = false;
+ bdrv_child_refresh_perms(bs, s->children[i].child, &error_abort);
+
+ if (local_err) {
+ error_free(local_err);
+ return false;
+ }
+
+ return true;
+ }
+ }
+
+ return false;
+}
+
static int quorum_valid_threshold(int threshold, int num_children, Error **errp)
{
@@ -1195,6 +1256,7 @@ static BlockDriver bdrv_quorum = {
.is_filter = true,
.bdrv_recurse_is_first_non_filter = quorum_recurse_is_first_non_filter,
+ .bdrv_recurse_can_replace = quorum_recurse_can_replace,
.strong_runtime_opts = quorum_strong_runtime_opts,
};
--
2.21.0
next prev parent reply other threads:[~2019-09-20 15:59 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-20 15:27 [PATCH 00/22] block: Fix check_to_replace_node() Max Reitz
2019-09-20 15:27 ` [PATCH 01/22] blockdev: Allow external snapshots everywhere Max Reitz
2019-09-25 11:45 ` Vladimir Sementsov-Ogievskiy
2019-09-20 15:27 ` [PATCH 02/22] blockdev: Allow resizing everywhere Max Reitz
2019-09-25 11:46 ` Vladimir Sementsov-Ogievskiy
2019-09-20 15:27 ` [PATCH 03/22] block: Drop bdrv_is_first_non_filter() Max Reitz
2019-09-25 11:46 ` Vladimir Sementsov-Ogievskiy
2019-09-20 15:27 ` [PATCH 04/22] iotests: Let 041 use -blockdev for quorum children Max Reitz
2019-09-25 11:51 ` Vladimir Sementsov-Ogievskiy
2019-09-20 15:27 ` [PATCH 05/22] quorum: Fix child permissions Max Reitz
2019-09-25 11:56 ` Vladimir Sementsov-Ogievskiy
2019-09-26 11:02 ` Max Reitz
2019-09-20 15:27 ` [PATCH 06/22] block: Add bdrv_recurse_can_replace() Max Reitz
2019-09-25 12:39 ` Vladimir Sementsov-Ogievskiy
2019-09-26 11:03 ` Max Reitz
2019-09-20 15:27 ` [PATCH 07/22] blkverify: Implement .bdrv_recurse_can_replace() Max Reitz
2019-09-25 12:56 ` Vladimir Sementsov-Ogievskiy
2019-09-26 11:06 ` Max Reitz
2019-09-20 15:27 ` [PATCH 08/22] quorum: Store children in own structure Max Reitz
2019-09-25 13:21 ` Vladimir Sementsov-Ogievskiy
2019-09-26 11:07 ` Max Reitz
2019-09-20 15:27 ` [PATCH 09/22] quorum: Add QuorumChild.to_be_replaced Max Reitz
2019-09-25 13:45 ` Vladimir Sementsov-Ogievskiy
2019-09-26 11:13 ` Max Reitz
2019-09-20 15:27 ` Max Reitz [this message]
2019-09-25 13:39 ` [PATCH 10/22] quorum: Implement .bdrv_recurse_can_replace() Vladimir Sementsov-Ogievskiy
2019-09-26 11:12 ` Max Reitz
2019-09-25 14:12 ` Vladimir Sementsov-Ogievskiy
2019-09-26 11:17 ` Max Reitz
2019-09-25 14:14 ` Vladimir Sementsov-Ogievskiy
2019-09-20 15:27 ` [PATCH 11/22] block: Use bdrv_recurse_can_replace() Max Reitz
2019-09-20 15:27 ` [PATCH 12/22] block: Remove bdrv_recurse_is_first_non_filter() Max Reitz
2019-09-25 14:16 ` Vladimir Sementsov-Ogievskiy
2019-09-20 15:27 ` [PATCH 13/22] mirror: Double-check immediately before replacing Max Reitz
2019-09-20 15:27 ` [PATCH 14/22] quorum: Stop marking it as a filter Max Reitz
2019-09-26 12:43 ` Vladimir Sementsov-Ogievskiy
2019-09-20 15:27 ` [PATCH 15/22] mirror: Prevent loops Max Reitz
2019-09-26 13:08 ` Vladimir Sementsov-Ogievskiy
2019-10-02 12:36 ` Max Reitz
2019-09-20 15:27 ` [PATCH 16/22] iotests: Use complete_and_wait() in 155 Max Reitz
2019-09-26 13:11 ` Vladimir Sementsov-Ogievskiy
2019-09-20 15:27 ` [PATCH 17/22] iotests: Add VM.assert_block_path() Max Reitz
2019-09-26 14:07 ` Vladimir Sementsov-Ogievskiy
2019-10-02 12:40 ` Max Reitz
2019-10-02 13:51 ` Vladimir Sementsov-Ogievskiy
2019-09-20 15:28 ` [PATCH 18/22] iotests: Resolve TODOs in 041 Max Reitz
2019-09-26 14:09 ` Vladimir Sementsov-Ogievskiy
2019-09-20 15:28 ` [PATCH 19/22] iotests: Use self.image_len in TestRepairQuorum Max Reitz
2019-09-26 14:13 ` Vladimir Sementsov-Ogievskiy
2019-10-02 12:42 ` Max Reitz
2019-09-20 15:28 ` [PATCH 20/22] iotests: Add tests for invalid Quorum @replaces Max Reitz
2019-09-26 14:30 ` Vladimir Sementsov-Ogievskiy
2019-10-02 12:43 ` Max Reitz
2019-09-20 15:28 ` [PATCH 21/22] iotests: Check that @replaces can replace filters Max Reitz
2019-09-26 14:42 ` Vladimir Sementsov-Ogievskiy
2019-09-20 15:28 ` [PATCH 22/22] iotests: Mirror must not attempt to create loops Max Reitz
2019-09-26 15:03 ` Vladimir Sementsov-Ogievskiy
2019-10-02 12:46 ` Max Reitz
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190920152804.12875-11-mreitz@redhat.com \
--to=mreitz@redhat.com \
--cc=berto@igalia.com \
--cc=kwolf@redhat.com \
--cc=qemu-block@nongnu.org \
--cc=qemu-devel@nongnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).