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[Qemu-devel] [PATCH 11/11] sheepdog: fix loadvm operation
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PATCH 11/11] sheepdog: fix loadvm operation |
Date: |
Fri, 26 Apr 2013 13:44:42 +0200 |
From: Liu Yuan <address@hidden>
Currently the 'loadvm' opertaion works as following:
1. switch to the snapshot
2. mark current working VDI as a snapshot
3. rely on sd_create_branch to create a new working VDI based on the snapshot
This works not the same as other format as QCOW2. For e.g,
qemu > savevm # get a live snapshot snap1
qemu > savevm # snap2
qemu > loadvm 1 # This will steally create snap3 of the working VDI
Which will result in following snapshot chain:
base <-- snap1 <-- snap2 <-- snap3
^
|
working VDI
snap3 was unnecessarily created and might be annoying users.
This patch discard the unnecessary 'snap3' creation. and implement
rollback(loadvm) operation to the specified snapshot by
1. switch to the snapshot
2. delete working VDI
3. rely on sd_create_branch to create a new working VDI based on the snapshot
The snapshot chain for above example will be:
base <-- snap1 <-- snap2
^
|
working VDI
Cc: address@hidden
Cc: MORITA Kazutaka <address@hidden>
Cc: Kevin Wolf <address@hidden>
Cc: Stefan Hajnoczi <address@hidden>
Signed-off-by: Liu Yuan <address@hidden>
Reviewed-by: MORITA Kazutaka <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
block/sheepdog.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 53 insertions(+), 1 deletion(-)
diff --git a/block/sheepdog.c b/block/sheepdog.c
index 77e21fd..21a4edf 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -36,6 +36,7 @@
#define SD_OP_GET_VDI_INFO 0x14
#define SD_OP_READ_VDIS 0x15
#define SD_OP_FLUSH_VDI 0x16
+#define SD_OP_DEL_VDI 0x17
#define SD_FLAG_CMD_WRITE 0x01
#define SD_FLAG_CMD_COW 0x02
@@ -1666,6 +1667,43 @@ out:
sd_finish_aiocb(acb);
}
+/* Delete current working VDI on the snapshot chain */
+static bool sd_delete(BDRVSheepdogState *s)
+{
+ unsigned int wlen = SD_MAX_VDI_LEN, rlen = 0;
+ SheepdogVdiReq hdr = {
+ .opcode = SD_OP_DEL_VDI,
+ .vdi_id = s->inode.vdi_id,
+ .data_length = wlen,
+ .flags = SD_FLAG_CMD_WRITE,
+ };
+ SheepdogVdiRsp *rsp = (SheepdogVdiRsp *)&hdr;
+ int fd, ret;
+
+ fd = connect_to_sdog(s);
+ if (fd < 0) {
+ return false;
+ }
+
+ ret = do_req(fd, (SheepdogReq *)&hdr, s->name, &wlen, &rlen);
+ closesocket(fd);
+ if (ret) {
+ return false;
+ }
+ switch (rsp->result) {
+ case SD_RES_NO_VDI:
+ error_report("%s was already deleted", s->name);
+ /* fall through */
+ case SD_RES_SUCCESS:
+ break;
+ default:
+ error_report("%s, %s", sd_strerror(rsp->result), s->name);
+ return false;
+ }
+
+ return true;
+}
+
/*
* Create a writable VDI from a snapshot
*/
@@ -1674,12 +1712,20 @@ static int sd_create_branch(BDRVSheepdogState *s)
int ret, fd;
uint32_t vid;
char *buf;
+ bool deleted;
dprintf("%" PRIx32 " is snapshot.\n", s->inode.vdi_id);
buf = g_malloc(SD_INODE_SIZE);
- ret = do_sd_create(s, s->name, s->inode.vdi_size, s->inode.vdi_id, &vid,
1);
+ /*
+ * Even If deletion fails, we will just create extra snapshot based on
+ * the workding VDI which was supposed to be deleted. So no need to
+ * false bail out.
+ */
+ deleted = sd_delete(s);
+ ret = do_sd_create(s, s->name, s->inode.vdi_size, s->inode.vdi_id, &vid,
+ !deleted);
if (ret) {
goto out;
}
@@ -1995,6 +2041,12 @@ cleanup:
return ret;
}
+/*
+ * We implement rollback(loadvm) operation to the specified snapshot by
+ * 1) switch to the snapshot
+ * 2) rely on sd_create_branch to delete working VDI and
+ * 3) create a new working VDI based on the speicified snapshot
+ */
static int sd_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
{
BDRVSheepdogState *s = bs->opaque;
--
1.8.1.4
- [Qemu-devel] [PATCH 06/11] qemu-iotests: filter QEMU_PROG in 051.out, (continued)
- [Qemu-devel] [PATCH 06/11] qemu-iotests: filter QEMU_PROG in 051.out, Stefan Hajnoczi, 2013/04/26
- [Qemu-devel] [PATCH 07/11] ide: refuse WIN_READ_NATIVE_MAX on empty device, Stefan Hajnoczi, 2013/04/26
- [Qemu-devel] [PATCH 07/11] sheepdog: cleanup find_vdi_name, Stefan Hajnoczi, 2013/04/26
- [Qemu-devel] [PATCH 08/11] sheepdog: add SD_RES_READONLY result code, Stefan Hajnoczi, 2013/04/26
- [Qemu-devel] [PATCH 09/11] block: ssh: Use libssh2_sftp_fsync (if supported by libssh2) to flush to disk., Stefan Hajnoczi, 2013/04/26
- [Qemu-devel] [PATCH 08/11] block: Add support for Secure Shell (ssh) block device., Stefan Hajnoczi, 2013/04/26
- [Qemu-devel] [PATCH 09/11] sheepdog: add helper function to reload inode, Stefan Hajnoczi, 2013/04/26
- [Qemu-devel] [PATCH 10/11] sheepdog: resend write requests when SD_RES_READONLY is received, Stefan Hajnoczi, 2013/04/26
- [Qemu-devel] [PATCH 10/11] iotests: Add 'check -ssh' option to test Secure Shell block device., Stefan Hajnoczi, 2013/04/26
- [Qemu-devel] [PATCH 11/11] rbd: add an asynchronous flush, Stefan Hajnoczi, 2013/04/26
- [Qemu-devel] [PATCH 11/11] sheepdog: fix loadvm operation,
Stefan Hajnoczi <=