[Qemu-devel] [PATCH v7 0/3] qemu-img: Document --force-share / -U

[Qemu-devel] [PATCH v7 0/3] qemu-img: Document --force-share / -U

[Fam Zheng]

v7: Tweak wording again "allowing concurrent writers" -> "allowing other QEMU
    processes to open it in write mode". [Eric, Stefan, Kevin]
    Add patch to document share-rw. [Stefan]

v6: Tweak wording ("concurrent writers"). [Max]

Fam Zheng (3):
  qemu-img.texi: Clean up parameter list
  qemu-img: Document --force-share / -U
  docs: Document share-rw property more thoroughly

 docs/qemu-block-drivers.texi | 10 ++++++
 qemu-img.texi                | 74 ++++++++++++++++++++++++++++----------------
 2 files changed, 57 insertions(+), 27 deletions(-)

-- 
2.14.3

[Qemu-devel] [PATCH v7 1/3] qemu-img.texi: Clean up parameter list

[Fam Zheng]

Split options out of the "@table @var" section and create a "@table
@option", then use whitespaces and blank lines consistently.

Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
---
 qemu-img.texi | 66 +++++++++++++++++++++++++++++++++++------------------------
 1 file changed, 39 insertions(+), 27 deletions(-)

diff --git a/qemu-img.texi b/qemu-img.texi
index fdcf120f36..60a0e080c6 100644
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -33,38 +33,14 @@ The following commands are supported:
 
 Command parameters:
 @table @var
+
 @item filename
- is a disk image filename
-
-@item --object @var{objectdef}
-
-is a QEMU user creatable object definition. See the @code{qemu(1)} manual
-page for a description of the object properties. The most common object
-type is a @code{secret}, which is used to supply passwords and/or encryption
-keys.
-
-@item --image-opts
-
-Indicates that the source @var{filename} parameter is to be interpreted as a
-full option string, not a plain filename. This parameter is mutually
-exclusive with the @var{-f} parameter.
-
-@item --target-image-opts
-
-Indicates that the @var{output_filename} parameter(s) are to be interpreted as
-a full option string, not a plain filename. This parameter is mutually
-exclusive with the @var{-O} parameters. It is currently required to also use
-the @var{-n} parameter to skip image creation. This restriction may be relaxed
-in a future release.
+is a disk image filename
 
 @item fmt
 is the disk image format. It is guessed automatically in most cases. See below
 for a description of the supported disk formats.
 
-@item --backing-chain
-will enumerate information about backing files in a disk image chain. Refer
-below for further description.
-
 @item size
 is the disk image size in bytes. Optional suffixes @code{k} or @code{K}
 (kilobyte, 1024) @code{M} (megabyte, 1024k) and @code{G} (gigabyte, 1024M)
@@ -74,42 +50,78 @@ and T (terabyte, 1024G) are supported.  @code{b} is ignored.
 is the destination disk image filename
 
 @item output_fmt
- is the destination format
+is the destination format
+
 @item options
 is a comma separated list of format specific options in a
 name=value format. Use @code{-o ?} for an overview of the options supported
 by the used format or see the format descriptions below for details.
+
 @item snapshot_param
 is param used for internal snapshot, format is
 'snapshot.id=[ID],snapshot.name=[NAME]' or '[ID_OR_NAME]'
+
 @item snapshot_id_or_name
 is deprecated, use snapshot_param instead
 
+@end table
+
+@table @option
+
+@item --object @var{objectdef}
+is a QEMU user creatable object definition. See the @code{qemu(1)} manual
+page for a description of the object properties. The most common object
+type is a @code{secret}, which is used to supply passwords and/or encryption
+keys.
+
+@item --image-opts
+Indicates that the source @var{filename} parameter is to be interpreted as a
+full option string, not a plain filename. This parameter is mutually
+exclusive with the @var{-f} parameter.
+
+@item --target-image-opts
+Indicates that the @var{output_filename} parameter(s) are to be interpreted as
+a full option string, not a plain filename. This parameter is mutually
+exclusive with the @var{-O} parameters. It is currently required to also use
+the @var{-n} parameter to skip image creation. This restriction may be relaxed
+in a future release.
+
+@item --backing-chain
+will enumerate information about backing files in a disk image chain. Refer
+below for further description.
+
 @item -c
 indicates that target image must be compressed (qcow format only)
+
 @item -h
 with or without a command shows help and lists the supported formats
+
 @item -p
 display progress bar (compare, convert and rebase commands only).
 If the @var{-p} option is not used for a command that supports it, the
 progress is reported when the process receives a @code{SIGUSR1} or
 @code{SIGINFO} signal.
+
 @item -q
 Quiet mode - do not print any output (except errors). There's no progress bar
 in case both @var{-q} and @var{-p} options are used.
+
 @item -S @var{size}
 indicates the consecutive number of bytes that must contain only zeros
 for qemu-img to create a sparse image during conversion. This value is rounded
 down to the nearest 512 bytes. You may use the common size suffixes like
 @code{k} for kilobytes.
+
 @item -t @var{cache}
 specifies the cache mode that should be used with the (destination) file. See
 the documentation of the emulator's @code{-drive cache=...} option for allowed
 values.
+
 @item -T @var{src_cache}
 specifies the cache mode that should be used with the source file(s). See
 the documentation of the emulator's @code{-drive cache=...} option for allowed
 values.
+
 @end table
 
 Parameters to snapshot subcommand:
-- 
2.14.3

[Qemu-devel] [PATCH v7 2/3] qemu-img: Document --force-share / -U

[Fam Zheng]

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 qemu-img.texi | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/qemu-img.texi b/qemu-img.texi
index 60a0e080c6..8a26400adb 100644
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -86,6 +86,14 @@ exclusive with the @var{-O} parameters. It is currently required to also use
 the @var{-n} parameter to skip image creation. This restriction may be relaxed
 in a future release.
 
+@item --force-share (-U)
+If specified, @code{qemu-img} will open the image in shared mode, allowing
+other QEMU processes to open it in write mode. For example, this can be used to
+get the image information (with 'info' subcommand) when the image is used by a
+running guest.  Note that this could produce inconsistent results because of
+concurrent metadata changes, etc. This option is only allowed when opening
+images in read-only mode.
+
 @item --backing-chain
 will enumerate information about backing files in a disk image chain. Refer
 below for further description.
-- 
2.14.3

[Qemu-devel] [PATCH v7 3/3] docs: Document share-rw property more thoroughly

[Fam Zheng]

Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
---
 docs/qemu-block-drivers.texi | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/docs/qemu-block-drivers.texi b/docs/qemu-block-drivers.texi
index cd74767ed3..f1793692bb 100644
--- a/docs/qemu-block-drivers.texi
+++ b/docs/qemu-block-drivers.texi
@@ -845,6 +845,16 @@ QEMU transparently handles lock handover during shared storage migration.  For
 shared virtual disk images between multiple VMs, the "share-rw" device option
 should be used.
 
+By default, the guest has exclusive write access to its disk image. If the
+guest can safely share the disk image with other writers the @code{-device
+...,share-rw=on} parameter can be used.  This is only safe if the guest is
+running software, such as a cluster file system, that coordinates disk accesses
+to avoid corruption.
+
+Note that share-rw=on only declares the guest's ability to share the disk.
+Some QEMU features, such as image file formats, require exclusive write access
+to the disk image and this is unaffected by the share-rw=on option.
+
 Alternatively, locking can be fully disabled by "locking=off" block device
 option. In the command line, the option is usually in the form of
 "file.locking=off" as the protocol driver is normally placed as a "file" child
-- 
2.14.3

Re: [Qemu-devel] [PATCH v7 0/3] qemu-img: Document --force-share / -U

[Stefan Hajnoczi]

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On Fri, Feb 09, 2018 at 01:29:12PM +0800, Fam Zheng wrote:
> v7: Tweak wording again "allowing concurrent writers" -> "allowing other QEMU
>     processes to open it in write mode". [Eric, Stefan, Kevin]
>     Add patch to document share-rw. [Stefan]
> 
> v6: Tweak wording ("concurrent writers"). [Max]
> 
> Fam Zheng (3):
>   qemu-img.texi: Clean up parameter list
>   qemu-img: Document --force-share / -U
>   docs: Document share-rw property more thoroughly
> 
>  docs/qemu-block-drivers.texi | 10 ++++++
>  qemu-img.texi                | 74 ++++++++++++++++++++++++++++----------------
>  2 files changed, 57 insertions(+), 27 deletions(-)

Nice, thanks for being persistent!

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [Qemu-devel] [PATCH v7 0/3] qemu-img: Document --force-share / -U

[Kashyap Chamarthy]

On Fri, Feb 09, 2018 at 01:29:12PM +0800, Fam Zheng wrote:
> v7: Tweak wording again "allowing concurrent writers" -> "allowing other QEMU
>     processes to open it in write mode". [Eric, Stefan, Kevin]
>     Add patch to document share-rw. [Stefan]
> 
> v6: Tweak wording ("concurrent writers"). [Max]
> 
> Fam Zheng (3):
>   qemu-img.texi: Clean up parameter list
>   qemu-img: Document --force-share / -U
>   docs: Document share-rw property more thoroughly
> 
>  docs/qemu-block-drivers.texi | 10 ++++++
>  qemu-img.texi                | 74 ++++++++++++++++++++++++++++----------------
>  2 files changed, 57 insertions(+), 27 deletions(-)

Thanks!

Reviewed-by: Kashyap Chamarthy <kchamart@redhat.com>

-- 
/kashyap

Re: [Qemu-devel] [PATCH v7 0/3] qemu-img: Document --force-share / -U

[Kevin Wolf]

Am 09.02.2018 um 06:29 hat Fam Zheng geschrieben:
> v7: Tweak wording again "allowing concurrent writers" -> "allowing other QEMU
>     processes to open it in write mode". [Eric, Stefan, Kevin]
>     Add patch to document share-rw. [Stefan]
> 
> v6: Tweak wording ("concurrent writers"). [Max]
> 
> Fam Zheng (3):
>   qemu-img.texi: Clean up parameter list
>   qemu-img: Document --force-share / -U
>   docs: Document share-rw property more thoroughly

Thanks, applied to the block branch.

Kevin