[v1,3/10] Qemu: Cmd "block_set_hostcache" for dynamic cache change

Submitted by Supriya Kannery on June 15, 2012, 8:47 p.m.

Details

Message ID 20120615204730.9853.61858.sendpatchset@skannery.in.ibm.com
State New
Headers show

Commit Message

Supriya Kannery June 15, 2012, 8:47 p.m.
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 <supriyak@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(+)

Comments

Eric Blake June 15, 2012, 9:56 p.m.
On 06/15/2012 02:47 PM, Supriya Kannery wrote:
> 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 <supriyak@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(+)

Doesn't this also need to touch qapi-schema.json?
[/me reads full patch]
Oh, you did - but your diffstat is stale.  It might be worth figuring
out what in your workflow leads to stale diffstats.

> 
> Index: qemu/block.c
> ===================================================================
> --- qemu.orig/block.c
> +++ qemu/block.c
> @@ -858,6 +858,35 @@ 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();
> +    ret = bdrv_flush(bs);
> +    if (ret != 0) {
> +        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);

Yuck.  This is bad, and why 'transaction' was invented.  Any time you
close() before open() you risk completely losing the file...

> +    if (ret < 0) {
> +        /* Reopen failed. Try to open with original flags */
> +        qerror_report(QERR_OPEN_FILE_FAILED, bs->filename);
> +        ret = bdrv_open(bs, bs->filename, open_flags, drv);
> +        if (ret < 0) {
> +            /* Reopen failed with orig and modified flags */
> +            abort();

and an abort() is not a nice reaction to that.

I think we should rebase the series to do the safe reopen prior to
adding this command (at least, just judging by the title of 4/10), to
avoid intermediate bad code.


> @@ -808,7 +808,6 @@ ETEXI
>          .mhandler.cmd = hmp_migrate,
>      },
>  
> -
>  STEXI

Spurious whitespace change.


> +
> +SQMP
> +block_set_hostcache

QMP commands favor '-' over '_'; this should be 'block-set-hostcache'.


> Index: qemu/qapi-schema.json
> ===================================================================
> --- qemu.orig/qapi-schema.json
> +++ qemu/qapi-schema.json
> @@ -1598,6 +1598,22 @@
>  { 'command': 'block_set_io_throttle',
>    'data': { 'device': 'str', 'bps': 'int', 'bps_rd': 'int', 'bps_wr': 'int',
>              'iops': 'int', 'iops_rd': 'int', 'iops_wr': 'int' } }
> +##
> +# @block_set_hostcache:
> +#
> +# Change host pagecache setting of a block device
> +#
> +# @device: name of the block device
> +#
> +# @option: hostcache setting (true/false)
> +#
> +# Returns: Nothing on success
> +#          If @device is not a valid block device, DeviceNotFound

What happens if the device is valid, but the setting cannot be changed
(perhaps because reopen has not been implemented for that driver)?
Jeff Cody June 20, 2012, 6:18 p.m.
On 06/15/2012 04:47 PM, Supriya Kannery wrote:
> 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 <supriyak@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
> @@ -858,6 +858,35 @@ 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();
> +    ret = bdrv_flush(bs);
> +    if (ret != 0) {
> +        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_OPEN_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)
>  {
>      bdrv_flush(bs);
> @@ -953,6 +982,34 @@ void bdrv_drain_all(void)
>      }
>  }
>  
> +int bdrv_change_hostcache(BlockDriverState *bs, bool enable)
> +{
> +    int bdrv_flags = bs->open_flags;
> +
> +    /* set hostcache flags (without changing WCE/flush bits) */
> +    if (enable) {
> +        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) {
> +        printf("no need to change\n");
> +        return 0;
> +    }
> +
> +    if (bdrv_is_inserted(bs)) {
> +        /* Reopen file with changed set of flags */
> +        bdrv_flags &= ~BDRV_O_CACHE_WB;
> +        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
> @@ -128,6 +128,7 @@ 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);
> @@ -177,6 +178,7 @@ int 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
> @@ -1198,3 +1198,27 @@ BlockJobInfoList *qmp_query_block_jobs(E
>      bdrv_iterate(do_qmp_query_block_jobs_one, &prev);
>      return dummy.next;
>  }
> +
> +
> +/*
> + * Change host page cache setting while guest is running.
> +*/
> +void qmp_block_set_hostcache(const char *device, bool enable,
> +                             Error **errp)
> +{
> +    BlockDriverState *bs = NULL;
> +
> +    /* Validate device */
> +    bs = bdrv_find(device);
> +    if (!bs) {
> +        error_set(errp, QERR_DEVICE_NOT_FOUND, device);
> +        return;
> +    }
> +
> +    if (bdrv_change_hostcache(bs, enable)) {
> +        error_set(errp, QERR_HOSTCACHE_NOT_CHANGED, device);
> +    }
> +
> +    return;
> +}
> +
> Index: qemu/hmp-commands.hx
> ===================================================================
> --- qemu.orig/hmp-commands.hx
> +++ qemu/hmp-commands.hx
> @@ -808,7 +808,6 @@ ETEXI
>          .mhandler.cmd = hmp_migrate,
>      },
>  
> -
>  STEXI
>  @item migrate [-d] [-b] [-i] @var{uri}
>  @findex migrate
> @@ -1314,6 +1313,21 @@ client.  @var{keep} changes the password
>  ETEXI
>  
>      {
> +        .name       = "block_set_hostcache",
> +        .args_type  = "device:B,option:b",
> +        .params     = "device on|off",
> +        .help       = "Change setting of host pagecache",
> +        .mhandler.cmd = hmp_block_set_hostcache,
> +    },
> +
> +STEXI
> +@item block_set_hostcache @var{device} @var{option}
> +@findex block_set_hostcache
> +Change host pagecache setting of a block device while guest is running.
> +ETEXI
> +
> +
> +    {
>          .name       = "expire_password",
>          .args_type  = "protocol:s,time:s",
>          .params     = "protocol time",
> Index: qemu/qmp-commands.hx
> ===================================================================
> --- qemu.orig/qmp-commands.hx
> +++ qemu/qmp-commands.hx
> @@ -821,7 +821,31 @@ Example:
>  
>  EQMP
>  
> +
>      {
> +        .name       = "block_set_hostcache",
> +        .args_type  = "device:B,option:b",
> +        .mhandler.cmd_new = qmp_block_set_hostcache,

The QAPI commands need to go through the marshaller - this needs to be:
           .mhandler.cmd_new = qmp_marshal_input_block_set_hostcache,

(qmp_marshal_input_block_set_hostcache is automatically generated, and
it will call qmp_block_set_hostcache)

> +    },
> +
> +SQMP
> +block_set_hostcache
> +-------------------
> +
> +Change host pagecache setting of a block device
> +
> +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",
>          .mhandler.cmd_new = qmp_marshal_input_balloon,
> Index: qemu/qapi-schema.json
> ===================================================================
> --- qemu.orig/qapi-schema.json
> +++ qemu/qapi-schema.json
> @@ -1598,6 +1598,22 @@
>  { 'command': 'block_set_io_throttle',
>    'data': { 'device': 'str', 'bps': 'int', 'bps_rd': 'int', 'bps_wr': 'int',
>              'iops': 'int', 'iops_rd': 'int', 'iops_wr': 'int' } }
> +##
> +# @block_set_hostcache:
> +#
> +# Change host pagecache setting of a block device
> +#
> +# @device: name of the block device
> +#
> +# @option: hostcache setting (true/false)
> +#
> +# Returns: Nothing on success
> +#          If @device is not a valid block device, DeviceNotFound
> +#
> +# Since: 1.2
> +##
> +{ 'command': 'block_set_hostcache',
> +  'data': { 'device': 'str', 'option': 'bool' } }
>  
>  ##
>  # @block-stream:
> Index: qemu/hmp.c
> ===================================================================
> --- qemu.orig/hmp.c
> +++ qemu/hmp.c
> @@ -836,6 +836,15 @@ void hmp_block_set_io_throttle(Monitor *
>      hmp_handle_error(mon, &err);
>  }
>  
> +void hmp_block_set_hostcache(Monitor *mon, const QDict *qdict)
> +{
> +    Error *err = NULL;
> +
> +    qmp_block_set_hostcache(qdict_get_str(qdict, "device"),
> +                              qdict_get_bool(qdict, "option"), &err);
> +    hmp_handle_error(mon, &err);
> +}
> +
>  void hmp_block_stream(Monitor *mon, const QDict *qdict)
>  {
>      Error *error = NULL;
> Index: qemu/hmp.h
> ===================================================================
> --- qemu.orig/hmp.h
> +++ qemu/hmp.h
> @@ -64,5 +64,6 @@ void hmp_device_del(Monitor *mon, const 
>  void hmp_dump_guest_memory(Monitor *mon, const QDict *qdict);
>  void hmp_netdev_add(Monitor *mon, const QDict *qdict);
>  void hmp_netdev_del(Monitor *mon, const QDict *qdict);
> +void hmp_block_set_hostcache(Monitor *mon, const QDict *qdict);
>  
>  #endif
> 
>
Kevin Wolf July 4, 2012, 6:30 a.m.
Am 04.07.2012 07:10, schrieb Shrinidhi Joshi:
> Updated patch to auto generate qmp_marshal_input_block_set_hostcache
> 
> --------------------------------------------------------------------
> 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 <supriyak@linux.vnet.ibm.com>
> 
> Signed-off-by: Shrinidhi Joshi <spjoshi31@gmail.com>

Please use git-send-email for sending patches. A line-wrapped
HTML-formatted patch like this cannot be applied and is useless.

Kevin
Kevin Wolf July 9, 2012, 2:52 p.m.
Am 15.06.2012 22:47, schrieb Supriya Kannery:
> 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 <supriyak@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
> @@ -858,6 +858,35 @@ 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();

bdrv_drain_all() should be used instead.

> +    ret = bdrv_flush(bs);
> +    if (ret != 0) {
> +        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_OPEN_FILE_FAILED, bs->filename);
> +        ret = bdrv_open(bs, bs->filename, open_flags, drv);
> +        if (ret < 0) {
> +            /* Reopen failed with orig and modified flags */
> +            abort();

Like Eric said, committing a broken version and then fixing it later in
the series isn't really nice. At least bs->drv = NULL; instead of
abort() is required. Starting with the real thing is probably even better.

Kevin
Luiz Capitulino July 11, 2012, 2:16 p.m.
On Sat, 16 Jun 2012 02:17:30 +0530
Supriya Kannery <supriyak@linux.vnet.ibm.com> wrote:

> 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 <supriyak@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
> @@ -858,6 +858,35 @@ 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();
> +    ret = bdrv_flush(bs);
> +    if (ret != 0) {
> +        qerror_report(QERR_DATA_SYNC_FAILED, bs->device_name);

Please, use error_set() instead of qerror_report() and as Kevin said IOError
seems enough here.

> +        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_OPEN_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)
>  {
>      bdrv_flush(bs);
> @@ -953,6 +982,34 @@ void bdrv_drain_all(void)
>      }
>  }
>  
> +int bdrv_change_hostcache(BlockDriverState *bs, bool enable)
> +{
> +    int bdrv_flags = bs->open_flags;
> +
> +    /* set hostcache flags (without changing WCE/flush bits) */
> +    if (enable) {
> +        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) {
> +        printf("no need to change\n");
> +        return 0;
> +    }
> +
> +    if (bdrv_is_inserted(bs)) {
> +        /* Reopen file with changed set of flags */
> +        bdrv_flags &= ~BDRV_O_CACHE_WB;
> +        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
> @@ -128,6 +128,7 @@ 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);
> @@ -177,6 +178,7 @@ int 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
> @@ -1198,3 +1198,27 @@ BlockJobInfoList *qmp_query_block_jobs(E
>      bdrv_iterate(do_qmp_query_block_jobs_one, &prev);
>      return dummy.next;
>  }
> +
> +
> +/*
> + * Change host page cache setting while guest is running.
> +*/
> +void qmp_block_set_hostcache(const char *device, bool enable,
> +                             Error **errp)
> +{
> +    BlockDriverState *bs = NULL;
> +
> +    /* Validate device */
> +    bs = bdrv_find(device);
> +    if (!bs) {
> +        error_set(errp, QERR_DEVICE_NOT_FOUND, device);
> +        return;
> +    }
> +
> +    if (bdrv_change_hostcache(bs, enable)) {
> +        error_set(errp, QERR_HOSTCACHE_NOT_CHANGED, device);
> +    }
> +
> +    return;
> +}
> +
> Index: qemu/hmp-commands.hx
> ===================================================================
> --- qemu.orig/hmp-commands.hx
> +++ qemu/hmp-commands.hx
> @@ -808,7 +808,6 @@ ETEXI
>          .mhandler.cmd = hmp_migrate,
>      },
>  
> -
>  STEXI
>  @item migrate [-d] [-b] [-i] @var{uri}
>  @findex migrate
> @@ -1314,6 +1313,21 @@ client.  @var{keep} changes the password
>  ETEXI
>  
>      {
> +        .name       = "block_set_hostcache",
> +        .args_type  = "device:B,option:b",
> +        .params     = "device on|off",
> +        .help       = "Change setting of host pagecache",
> +        .mhandler.cmd = hmp_block_set_hostcache,
> +    },
> +
> +STEXI
> +@item block_set_hostcache @var{device} @var{option}
> +@findex block_set_hostcache
> +Change host pagecache setting of a block device while guest is running.
> +ETEXI
> +
> +
> +    {
>          .name       = "expire_password",
>          .args_type  = "protocol:s,time:s",
>          .params     = "protocol time",
> Index: qemu/qmp-commands.hx
> ===================================================================
> --- qemu.orig/qmp-commands.hx
> +++ qemu/qmp-commands.hx
> @@ -821,7 +821,31 @@ Example:
>  
>  EQMP
>  
> +
>      {
> +        .name       = "block_set_hostcache",
> +        .args_type  = "device:B,option:b",
> +        .mhandler.cmd_new = qmp_block_set_hostcache,
> +    },
> +
> +SQMP
> +block_set_hostcache
> +-------------------
> +
> +Change host pagecache setting of a block device
> +
> +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",
>          .mhandler.cmd_new = qmp_marshal_input_balloon,
> Index: qemu/qapi-schema.json
> ===================================================================
> --- qemu.orig/qapi-schema.json
> +++ qemu/qapi-schema.json
> @@ -1598,6 +1598,22 @@
>  { 'command': 'block_set_io_throttle',
>    'data': { 'device': 'str', 'bps': 'int', 'bps_rd': 'int', 'bps_wr': 'int',
>              'iops': 'int', 'iops_rd': 'int', 'iops_wr': 'int' } }
> +##
> +# @block_set_hostcache:
> +#
> +# Change host pagecache setting of a block device
> +#
> +# @device: name of the block device
> +#
> +# @option: hostcache setting (true/false)
> +#
> +# Returns: Nothing on success
> +#          If @device is not a valid block device, DeviceNotFound
> +#
> +# Since: 1.2
> +##
> +{ 'command': 'block_set_hostcache',
> +  'data': { 'device': 'str', 'option': 'bool' } }
>  
>  ##
>  # @block-stream:
> Index: qemu/hmp.c
> ===================================================================
> --- qemu.orig/hmp.c
> +++ qemu/hmp.c
> @@ -836,6 +836,15 @@ void hmp_block_set_io_throttle(Monitor *
>      hmp_handle_error(mon, &err);
>  }
>  
> +void hmp_block_set_hostcache(Monitor *mon, const QDict *qdict)
> +{
> +    Error *err = NULL;
> +
> +    qmp_block_set_hostcache(qdict_get_str(qdict, "device"),
> +                              qdict_get_bool(qdict, "option"), &err);
> +    hmp_handle_error(mon, &err);
> +}
> +
>  void hmp_block_stream(Monitor *mon, const QDict *qdict)
>  {
>      Error *error = NULL;
> Index: qemu/hmp.h
> ===================================================================
> --- qemu.orig/hmp.h
> +++ qemu/hmp.h
> @@ -64,5 +64,6 @@ void hmp_device_del(Monitor *mon, const 
>  void hmp_dump_guest_memory(Monitor *mon, const QDict *qdict);
>  void hmp_netdev_add(Monitor *mon, const QDict *qdict);
>  void hmp_netdev_del(Monitor *mon, const QDict *qdict);
> +void hmp_block_set_hostcache(Monitor *mon, const QDict *qdict);
>  
>  #endif
>
Supriya Kannery July 29, 2012, 7:33 a.m.
On 06/16/2012 03:26 AM, Eric Blake wrote:
> On 06/15/2012 02:47 PM, Supriya Kannery wrote:
>> 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<supriyak@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(+)
>
> Doesn't this also need to touch qapi-schema.json?
> [/me reads full patch]
> Oh, you did - but your diffstat is stale.  It might be worth figuring
> out what in your workflow leads to stale diffstats.
>
>>
>> Index: qemu/block.c
>> ===================================================================
>> --- qemu.orig/block.c
>> +++ qemu/block.c
>> @@ -858,6 +858,35 @@ 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();
>> +    ret = bdrv_flush(bs);
>> +    if (ret != 0) {
>> +        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);
>
> Yuck.  This is bad, and why 'transaction' was invented.  Any time you
> close() before open() you risk completely losing the file...
>
>> +    if (ret<  0) {
>> +        /* Reopen failed. Try to open with original flags */
>> +        qerror_report(QERR_OPEN_FILE_FAILED, bs->filename);
>> +        ret = bdrv_open(bs, bs->filename, open_flags, drv);
>> +        if (ret<  0) {
>> +            /* Reopen failed with orig and modified flags */
>> +            abort();
>
> and an abort() is not a nice reaction to that.
>
> I think we should rebase the series to do the safe reopen prior to
> adding this command (at least, just judging by the title of 4/10), to
> avoid intermediate bad code.
>
>

  Yes, will reorder the patches to have safe reopen done first and
then block_set_hostcache use it.

-thanks, Supriya
Supriya Kannery July 29, 2012, 7:56 a.m.
On 07/11/2012 07:46 PM, Luiz Capitulino wrote:
> On Sat, 16 Jun 2012 02:17:30 +0530
> Supriya Kannery<supriyak@linux.vnet.ibm.com>  wrote:
>
>> 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<supriyak@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
>> @@ -858,6 +858,35 @@ 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();
>> +    ret = bdrv_flush(bs);
>> +    if (ret != 0) {
>> +        qerror_report(QERR_DATA_SYNC_FAILED, bs->device_name);
>
> Please, use error_set() instead of qerror_report() and as Kevin said IOError
> seems enough here.
>

Sure, will replace qemu_aio_flush() with bdrv_drain_all()
and qerror_report() with error_set().

Combination of bdrv_drain_all() and bdrv_flush(), should
help in flushing out the specific disk.

-thanks, Supriya

Patch hide | download patch | download mbox

Index: qemu/block.c
===================================================================
--- qemu.orig/block.c
+++ qemu/block.c
@@ -858,6 +858,35 @@  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();
+    ret = bdrv_flush(bs);
+    if (ret != 0) {
+        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_OPEN_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)
 {
     bdrv_flush(bs);
@@ -953,6 +982,34 @@  void bdrv_drain_all(void)
     }
 }
 
+int bdrv_change_hostcache(BlockDriverState *bs, bool enable)
+{
+    int bdrv_flags = bs->open_flags;
+
+    /* set hostcache flags (without changing WCE/flush bits) */
+    if (enable) {
+        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) {
+        printf("no need to change\n");
+        return 0;
+    }
+
+    if (bdrv_is_inserted(bs)) {
+        /* Reopen file with changed set of flags */
+        bdrv_flags &= ~BDRV_O_CACHE_WB;
+        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
@@ -128,6 +128,7 @@  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);
@@ -177,6 +178,7 @@  int 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
@@ -1198,3 +1198,27 @@  BlockJobInfoList *qmp_query_block_jobs(E
     bdrv_iterate(do_qmp_query_block_jobs_one, &prev);
     return dummy.next;
 }
+
+
+/*
+ * Change host page cache setting while guest is running.
+*/
+void qmp_block_set_hostcache(const char *device, bool enable,
+                             Error **errp)
+{
+    BlockDriverState *bs = NULL;
+
+    /* Validate device */
+    bs = bdrv_find(device);
+    if (!bs) {
+        error_set(errp, QERR_DEVICE_NOT_FOUND, device);
+        return;
+    }
+
+    if (bdrv_change_hostcache(bs, enable)) {
+        error_set(errp, QERR_HOSTCACHE_NOT_CHANGED, device);
+    }
+
+    return;
+}
+
Index: qemu/hmp-commands.hx
===================================================================
--- qemu.orig/hmp-commands.hx
+++ qemu/hmp-commands.hx
@@ -808,7 +808,6 @@  ETEXI
         .mhandler.cmd = hmp_migrate,
     },
 
-
 STEXI
 @item migrate [-d] [-b] [-i] @var{uri}
 @findex migrate
@@ -1314,6 +1313,21 @@  client.  @var{keep} changes the password
 ETEXI
 
     {
+        .name       = "block_set_hostcache",
+        .args_type  = "device:B,option:b",
+        .params     = "device on|off",
+        .help       = "Change setting of host pagecache",
+        .mhandler.cmd = hmp_block_set_hostcache,
+    },
+
+STEXI
+@item block_set_hostcache @var{device} @var{option}
+@findex block_set_hostcache
+Change host pagecache setting of a block device while guest is running.
+ETEXI
+
+
+    {
         .name       = "expire_password",
         .args_type  = "protocol:s,time:s",
         .params     = "protocol time",
Index: qemu/qmp-commands.hx
===================================================================
--- qemu.orig/qmp-commands.hx
+++ qemu/qmp-commands.hx
@@ -821,7 +821,31 @@  Example:
 
 EQMP
 
+
     {
+        .name       = "block_set_hostcache",
+        .args_type  = "device:B,option:b",
+        .mhandler.cmd_new = qmp_block_set_hostcache,
+    },
+
+SQMP
+block_set_hostcache
+-------------------
+
+Change host pagecache setting of a block device
+
+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",
         .mhandler.cmd_new = qmp_marshal_input_balloon,
Index: qemu/qapi-schema.json
===================================================================
--- qemu.orig/qapi-schema.json
+++ qemu/qapi-schema.json
@@ -1598,6 +1598,22 @@ 
 { 'command': 'block_set_io_throttle',
   'data': { 'device': 'str', 'bps': 'int', 'bps_rd': 'int', 'bps_wr': 'int',
             'iops': 'int', 'iops_rd': 'int', 'iops_wr': 'int' } }
+##
+# @block_set_hostcache:
+#
+# Change host pagecache setting of a block device
+#
+# @device: name of the block device
+#
+# @option: hostcache setting (true/false)
+#
+# Returns: Nothing on success
+#          If @device is not a valid block device, DeviceNotFound
+#
+# Since: 1.2
+##
+{ 'command': 'block_set_hostcache',
+  'data': { 'device': 'str', 'option': 'bool' } }
 
 ##
 # @block-stream:
Index: qemu/hmp.c
===================================================================
--- qemu.orig/hmp.c
+++ qemu/hmp.c
@@ -836,6 +836,15 @@  void hmp_block_set_io_throttle(Monitor *
     hmp_handle_error(mon, &err);
 }
 
+void hmp_block_set_hostcache(Monitor *mon, const QDict *qdict)
+{
+    Error *err = NULL;
+
+    qmp_block_set_hostcache(qdict_get_str(qdict, "device"),
+                              qdict_get_bool(qdict, "option"), &err);
+    hmp_handle_error(mon, &err);
+}
+
 void hmp_block_stream(Monitor *mon, const QDict *qdict)
 {
     Error *error = NULL;
Index: qemu/hmp.h
===================================================================
--- qemu.orig/hmp.h
+++ qemu/hmp.h
@@ -64,5 +64,6 @@  void hmp_device_del(Monitor *mon, const 
 void hmp_dump_guest_memory(Monitor *mon, const QDict *qdict);
 void hmp_netdev_add(Monitor *mon, const QDict *qdict);
 void hmp_netdev_del(Monitor *mon, const QDict *qdict);
+void hmp_block_set_hostcache(Monitor *mon, const QDict *qdict);
 
 #endif