[Qemu-devel] [PATCH 17/20] qemu-io: Use bdrv_parse_cache_mode() in reopen_f()

From: Kevin Wolf <kwolf@redhat.com>
To: qemu-block@nongnu.org
Cc: kwolf@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com
Subject: [Qemu-devel] [PATCH 17/20] qemu-io: Use bdrv_parse_cache_mode() in reopen_f()
Date: Fri, 18 Mar 2016 19:21:26 +0100	[thread overview]
Message-ID: <1458325289-17848-18-git-send-email-kwolf@redhat.com> (raw)
In-Reply-To: <1458325289-17848-1-git-send-email-kwolf@redhat.com>

We must forbid changing the WCE flag in bdrv_reopen() in the same patch,
as otherwise the behaviour would change so that the flag takes
precedence over the explicitly specified option.

The correct value of the WCE flag depends on the BlockBackend user (e.g.
guest device) and isn't a decision that the QMP client makes, so this
change is what we want.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c                    | 18 ++++++------------
 qemu-io-cmds.c             | 14 +++++++++++++-
 tests/qemu-iotests/142     |  2 +-
 tests/qemu-iotests/142.out |  2 +-
 4 files changed, 21 insertions(+), 15 deletions(-)

diff --git a/block.c b/block.c
index 4e95d01..3775e65 100644
--- a/block.c
+++ b/block.c
@@ -2028,18 +2028,12 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue,
 
     update_flags_from_options(&reopen_state->flags, opts);
 
-    /* If a guest device is attached, it owns WCE */
-    if (reopen_state->bs->blk && blk_get_attached_dev(reopen_state->bs->blk)) {
-        bool old_wce = bdrv_enable_write_cache(reopen_state->bs);
-        bool new_wce = (reopen_state->flags & BDRV_O_CACHE_WB);
-        if (old_wce != new_wce) {
-            error_setg(errp, "Cannot change cache.writeback: Device attached");
-            ret = -EINVAL;
-            goto error;
-        }
-    }
-    if (!reopen_state->bs->blk && !(reopen_state->flags & BDRV_O_CACHE_WB)) {
-        error_setg(errp, "Cannot disable cache.writeback: No BlockBackend");
+    /* WCE is a BlockBackend level option, can't change it */
+    bool old_wce = bdrv_enable_write_cache(reopen_state->bs);
+    bool new_wce = (reopen_state->flags & BDRV_O_CACHE_WB);
+
+    if (old_wce != new_wce) {
+        error_setg(errp, "Cannot change cache.writeback");
         ret = -EINVAL;
         goto error;
     }
diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
index e929d24..7de3754 100644
--- a/qemu-io-cmds.c
+++ b/qemu-io-cmds.c
@@ -2104,6 +2104,7 @@ static int reopen_f(BlockBackend *blk, int argc, char **argv)
     QDict *opts;
     int c;
     int flags = bs->open_flags;
+    bool writethrough = !blk_enable_write_cache(blk);
 
     BlockReopenQueue *brq;
     Error *local_err = NULL;
@@ -2111,7 +2112,7 @@ static int reopen_f(BlockBackend *blk, int argc, char **argv)
     while ((c = getopt(argc, argv, "c:o:r")) != -1) {
         switch (c) {
         case 'c':
-            if (bdrv_parse_cache_flags(optarg, &flags) < 0) {
+            if (bdrv_parse_cache_mode(optarg, &flags, &writethrough) < 0) {
                 error_report("Invalid cache option: %s", optarg);
                 return 0;
             }
@@ -2136,14 +2137,25 @@ static int reopen_f(BlockBackend *blk, int argc, char **argv)
         return qemuio_command_usage(&reopen_cmd);
     }
 
+    if (writethrough != blk_enable_write_cache(blk) &&
+        blk_get_attached_dev(blk))
+    {
+        error_report("Cannot change cache.writeback: Device attached");
+        qemu_opts_reset(&reopen_opts);
+        return 0;
+    }
+
     qopts = qemu_opts_find(&reopen_opts, NULL);
     opts = qopts ? qemu_opts_to_qdict(qopts, NULL) : NULL;
     qemu_opts_reset(&reopen_opts);
 
+    flags |= blk_enable_write_cache(blk) ? BDRV_O_CACHE_WB : 0;
     brq = bdrv_reopen_queue(NULL, bs, opts, flags);
     bdrv_reopen_multiple(brq, &local_err);
     if (local_err) {
         error_report_err(local_err);
+    } else {
+        blk_set_enable_write_cache(blk, !writethrough);
     }
 
     return 0;
diff --git a/tests/qemu-iotests/142 b/tests/qemu-iotests/142
index 8bbbfde..a035747 100755
--- a/tests/qemu-iotests/142
+++ b/tests/qemu-iotests/142
@@ -216,7 +216,7 @@ echo
 # BDS initialised with the json: pseudo-protocol, but still have it inherit
 # options from its parent node.
 
-hmp_cmds="qemu-io none0 \"reopen -o cache.writeback=off,cache.direct=on,cache.no-flush=on\"
+hmp_cmds="qemu-io none0 \"reopen -o cache.direct=on,cache.no-flush=on\"
 info block none0
 info block image
 info block blkdebug
diff --git a/tests/qemu-iotests/142.out b/tests/qemu-iotests/142.out
index c922490..3d5ef5f 100644
--- a/tests/qemu-iotests/142.out
+++ b/tests/qemu-iotests/142.out
@@ -414,7 +414,7 @@ cache.no-flush=on on backing-file
 
 --- Change cache mode in parent, child has explicit option in JSON ---
 
-    Cache mode:       writethrough, direct, ignore flushes
+    Cache mode:       writeback, direct, ignore flushes
     Cache mode:       writeback, direct, ignore flushes
     Cache mode:       writeback, direct, ignore flushes
     Cache mode:       writeback, ignore flushes
-- 
1.8.3.1
