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 <kw...@redhat.com> Reviewed-by: Max Reitz <mre...@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 0bd2eb2..1da7390 100644 --- a/block.c +++ b/block.c @@ -2027,18 +2027,12 @@ 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