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[Qemu-devel] [RFC PATCH] qemu-io: add drain/undrain cmd
From: |
Peter Lieven |
Subject: |
[Qemu-devel] [RFC PATCH] qemu-io: add drain/undrain cmd |
Date: |
Mon, 15 May 2017 12:02:43 +0200 |
Hi Block developers,
I would like to add a feature to Qemu to drain all traffic from a block so that
I can take external snaphosts without the risk to that in the middle of a write
operation. Its meant for cases where where QGA freeze/thaw is not available.
For me its enough to have this through qemu-io, but Kevin asked me to check
if its not worth to have a stable API for it and present it via QMP/HMP.
What are your thoughts?
Thanks,
Peter
---
qemu-io-cmds.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 78 insertions(+)
diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
index 312fc6d..49d82fe 100644
--- a/qemu-io-cmds.c
+++ b/qemu-io-cmds.c
@@ -1565,6 +1565,82 @@ static const cmdinfo_t flush_cmd = {
.oneline = "flush all in-core file state to disk",
};
+static const cmdinfo_t drain_cmd;
+
+static int drain_f(BlockBackend *blk, int argc, char **argv)
+{
+ BlockDriverState *bs = blk_bs(blk);
+ bool flush = false;
+ int c;
+
+ while ((c = getopt(argc, argv, "f")) != -1) {
+ switch (c) {
+ case 'f':
+ flush = true;
+ break;
+ default:
+ return qemuio_command_usage(&drain_cmd);
+ }
+ }
+
+ if (optind != argc) {
+ return qemuio_command_usage(&drain_cmd);
+ }
+
+
+ if (bs->quiesce_counter) {
+ printf("drain failed: device is already drained!\n");
+ return 1;
+ }
+
+ bdrv_drained_begin(bs); /* complete I/O */
+ if (flush) {
+ bdrv_flush(bs);
+ bdrv_drain(bs); /* in case flush left pending I/O */
+ printf("flushed all pending I/O\n");
+ }
+ printf("drain successful\n");
+ return 0;
+}
+
+static void drain_help(void)
+{
+ printf(
+"\n"
+" Drains all external I/O from the device\n"
+"\n"
+" -f, -- flush all in-core file state to disk\n"
+"\n");
+}
+
+static const cmdinfo_t drain_cmd = {
+ .name = "drain",
+ .cfunc = drain_f,
+ .args = "[-f]",
+ .argmin = 0,
+ .argmax = -1,
+ .oneline = "cease to send I/O to the device",
+ .help = drain_help
+};
+
+static int undrain_f(BlockBackend *blk, int argc, char **argv)
+{
+ BlockDriverState *bs = blk_bs(blk);
+ if (!bs->quiesce_counter) {
+ printf("undrain failed: device is not drained!\n");
+ return 1;
+ }
+ bdrv_drained_end(bs);
+ printf("undrain successful\n");
+ return 0;
+}
+
+static const cmdinfo_t undrain_cmd = {
+ .name = "undrain",
+ .cfunc = undrain_f,
+ .oneline = "continue I/O to a drained device",
+};
+
static int truncate_f(BlockBackend *blk, int argc, char **argv)
{
int64_t offset;
@@ -2296,6 +2372,8 @@ static void __attribute((constructor))
init_qemuio_commands(void)
qemuio_add_command(&aio_write_cmd);
qemuio_add_command(&aio_flush_cmd);
qemuio_add_command(&flush_cmd);
+ qemuio_add_command(&drain_cmd);
+ qemuio_add_command(&undrain_cmd);
qemuio_add_command(&truncate_cmd);
qemuio_add_command(&length_cmd);
qemuio_add_command(&info_cmd);
--
1.9.1
- [Qemu-devel] [RFC PATCH] qemu-io: add drain/undrain cmd,
Peter Lieven <=
- Re: [Qemu-devel] [RFC PATCH] qemu-io: add drain/undrain cmd, Fam Zheng, 2017/05/15
- Re: [Qemu-devel] [RFC PATCH] qemu-io: add drain/undrain cmd, Peter Lieven, 2017/05/15
- Re: [Qemu-devel] [RFC PATCH] qemu-io: add drain/undrain cmd, Fam Zheng, 2017/05/15
- Re: [Qemu-devel] [RFC PATCH] qemu-io: add drain/undrain cmd, Peter Lieven, 2017/05/15
- Re: [Qemu-devel] [RFC PATCH] qemu-io: add drain/undrain cmd, Fam Zheng, 2017/05/15
- Re: [Qemu-devel] [RFC PATCH] qemu-io: add drain/undrain cmd, Peter Lieven, 2017/05/15
- Re: [Qemu-devel] [RFC PATCH] qemu-io: add drain/undrain cmd, Fam Zheng, 2017/05/15
- Re: [Qemu-devel] [RFC PATCH] qemu-io: add drain/undrain cmd, Peter Lieven, 2017/05/15
- Re: [Qemu-devel] [RFC PATCH] qemu-io: add drain/undrain cmd, Fam Zheng, 2017/05/15
- Re: [Qemu-devel] [RFC PATCH] qemu-io: add drain/undrain cmd, Peter Lieven, 2017/05/15