New command "block_set_hostcache" added for dynamically changing
host pagecache setting of a block device.
Usage:
block_set_hostcache <device> <option>
<device> = block device
<option> = on/off
Example:
(qemu) block_set_hostcache ide0-hd0 off
Signed-off-by: Supriya Kannery <supri...@linux.vnet.ibm.com>
---
block.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
block.h | 2 ++
blockdev.c | 26 ++++++++++++++++++++++++++
blockdev.h | 2 ++
hmp-commands.hx | 14 ++++++++++++++
qmp-commands.hx | 27 +++++++++++++++++++++++++++
6 files changed, 125 insertions(+)
Index: qemu/block.c
===================================================================
--- qemu.orig/block.c
+++ qemu/block.c
@@ -702,6 +702,34 @@ unlink_and_fail:
return ret;
}
+int bdrv_reopen(BlockDriverState *bs, int bdrv_flags)
+{
+ BlockDriver *drv = bs->drv;
+ int ret = 0, open_flags;
+
+ /* Quiesce IO for the given block device */
+ qemu_aio_flush();
+ if (bdrv_flush(bs)) {
+ qerror_report(QERR_DATA_SYNC_FAILED, bs->device_name);
+ return ret;
+ }
+ open_flags = bs->open_flags;
+ bdrv_close(bs);
+
+ ret = bdrv_open(bs, bs->filename, bdrv_flags, drv);
+ if (ret < 0) {
+ /* Reopen failed. Try to open with original flags */
+ qerror_report(QERR_REOPEN_FILE_FAILED, bs->filename);
+ ret = bdrv_open(bs, bs->filename, open_flags, drv);
+ if (ret < 0) {
+ /* Reopen failed with orig and modified flags */
+ abort();
+ }
+ }
+
+ return ret;
+}
+
void bdrv_close(BlockDriverState *bs)
{
if (bs->drv) {
@@ -739,6 +767,32 @@ void bdrv_close_all(void)
}
}
+int bdrv_change_hostcache(BlockDriverState *bs, bool enable_host_cache)
+{
+ int bdrv_flags = bs->open_flags;
+
+ /* set hostcache flags (without changing WCE/flush bits) */
+ if (enable_host_cache) {
+ bdrv_flags &= ~BDRV_O_NOCACHE;
+ } else {
+ bdrv_flags |= BDRV_O_NOCACHE;
+ }
+
+ /* If no change in flags, no need to reopen */
+ if (bdrv_flags == bs->open_flags) {
+ return 0;
+ }
+
+ if (bdrv_is_inserted(bs)) {
+ /* Reopen file with changed set of flags */
+ return bdrv_reopen(bs, bdrv_flags);
+ } else {
+ /* Save hostcache change for future use */
+ bs->open_flags = bdrv_flags;
+ return 0;
+ }
+}
+
/* make a BlockDriverState anonymous by removing from bdrv_state list.
Also, NULL terminate the device_name to prevent double remove */
void bdrv_make_anon(BlockDriverState *bs)
Index: qemu/block.h
===================================================================
--- qemu.orig/block.h
+++ qemu/block.h
@@ -99,6 +99,7 @@ int bdrv_parse_cache_flags(const char *m
int bdrv_file_open(BlockDriverState **pbs, const char *filename, int flags);
int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
BlockDriver *drv);
+int bdrv_reopen(BlockDriverState *bs, int bdrv_flags);
void bdrv_close(BlockDriverState *bs);
int bdrv_attach_dev(BlockDriverState *bs, void *dev);
void bdrv_attach_dev_nofail(BlockDriverState *bs, void *dev);
@@ -133,6 +134,7 @@ void bdrv_commit_all(void);
int bdrv_change_backing_file(BlockDriverState *bs,
const char *backing_file, const char *backing_fmt);
void bdrv_register(BlockDriver *bdrv);
+int bdrv_change_hostcache(BlockDriverState *bs, bool enable_host_cache);
typedef struct BdrvCheckResult {
Index: qemu/blockdev.c
===================================================================
--- qemu.orig/blockdev.c
+++ qemu/blockdev.c
@@ -776,3 +776,29 @@ int do_block_resize(Monitor *mon, const
return 0;
}
+
+
+/*
+ * Change host page cache setting while guest is running.
+*/
+int do_block_set_hostcache(Monitor *mon, const QDict *qdict,
+ QObject **ret_data)
+{
+ BlockDriverState *bs = NULL;
+ int enable;
+ const char *device;
+
+ /* Validate device */
+ device = qdict_get_str(qdict, "device");
+ bs = bdrv_find(device);
+ if (!bs) {
+ qerror_report(QERR_DEVICE_NOT_FOUND, device);
+ return -1;
+ }
+
+ /* Read hostcache setting */
+ enable = qdict_get_bool(qdict, "option");
+ return bdrv_change_hostcache(bs, enable);
+
+}
+
Index: qemu/blockdev.h
===================================================================
--- qemu.orig/blockdev.h
+++ qemu/blockdev.h
@@ -65,5 +65,7 @@ int do_change_block(Monitor *mon, const
int do_drive_del(Monitor *mon, const QDict *qdict, QObject **ret_data);
int do_snapshot_blkdev(Monitor *mon, const QDict *qdict, QObject **ret_data);
int do_block_resize(Monitor *mon, const QDict *qdict, QObject **ret_data);
+int do_block_set_hostcache(Monitor *mon, const QDict *qdict,
+ QObject **ret_data);
#endif
Index: qemu/hmp-commands.hx
===================================================================
--- qemu.orig/hmp-commands.hx
+++ qemu/hmp-commands.hx
@@ -70,6 +70,20 @@ but should be used with extreme caution.
resizes image files, it can not resize block devices like LVM volumes.
ETEXI
+ {
+ .name = "block_set_hostcache",
+ .args_type = "device:B,option:b",
+ .params = "device on|off",
+ .help = "Change setting of host pagecache",
+ .user_print = monitor_user_noop,
+ .mhandler.cmd_new = do_block_set_hostcache,
+ },
+STEXI
+@item block_set_hostcache @var{device} @var{setting}
+@findex block_set_hostcache
+Change host pagecache setting of a block device while guest is running.
+ETEXI
+
{
.name = "eject",
Index: qemu/qmp-commands.hx
===================================================================
--- qemu.orig/qmp-commands.hx
+++ qemu/qmp-commands.hx
@@ -718,7 +718,34 @@ Example:
EQMP
+
{
+ .name = "block_set_hostcache",
+ .args_type = "device:B,option:b",
+ .params = "device on|off",
+ .help = "Change setting of host pagecache (true|false)",
+ .user_print = monitor_user_noop,
+ .mhandler.cmd_new = do_block_set_hostcache,
+ },
+
+SQMP
+block_set_hostcache
+-------------------
+
+Change host pagecache setting of a block device (on|off)
+
+Arguments:
+
+- "device": the device's ID, must be unique (json-string)
+- "option": hostcache setting (json-bool)
+
+Example:
+-> { "execute": "block_set_hostcache", "arguments": { "device": "ide0-hd0",
"option": false } }
+<- { "return": {} }
+
+EQMP
+
+ {
.name = "balloon",
.args_type = "value:M",
.params = "target",
