[pve-devel] [PATCH v2 storage 1/1] fix #3580: plugins: make preallocation mode selectable for qcow2 and raw images

[Fabian Ebner]

Am 28.09.21 um 15:07 schrieb Lorenz Stechauner:
> the plugins for file based storages
>   * BTRFS
>   * CIFS
>   * Dir
>   * Glusterfs
>   * NFS
> now allow the option 'preallocation'.
> 
> 'preallocation' can have four values:
>   * default
>   * off
>   * metadata
>   * falloc
>   * full
> see man pages for `qemu-img` for what these mean exactly. [0]
> 
> the defualt value was chosen to be
>   * qcow2: metadata (as previously)
>   * raw: off (I was unable to find any documentation on this, so
>      could only test this and found, that 'off' was the most
>      fitting.)

Yes, should be off. See raw_co_create in QEMU's block/file-posix.c

> 
> when using 'metadata' as preallocation mode, for raw images 'off'
> is used.
> 
> [0] https://qemu.readthedocs.io/en/latest/system/images.html#disk-image-file-formats
> 
> Signed-off-by: Lorenz Stechauner <l.stechauner at proxmox.com>
> ---
>   PVE/Storage/BTRFSPlugin.pm     |  1 +
>   PVE/Storage/CIFSPlugin.pm      |  1 +
>   PVE/Storage/DirPlugin.pm       |  1 +
>   PVE/Storage/GlusterfsPlugin.pm |  4 ++-
>   PVE/Storage/NFSPlugin.pm       |  1 +
>   PVE/Storage/Plugin.pm          | 48 +++++++++++++++++++++++++++++++++-
>   6 files changed, 54 insertions(+), 2 deletions(-)
> 
> diff --git a/PVE/Storage/BTRFSPlugin.pm b/PVE/Storage/BTRFSPlugin.pm
> index b30000b..97633a2 100644
> --- a/PVE/Storage/BTRFSPlugin.pm
> +++ b/PVE/Storage/BTRFSPlugin.pm
> @@ -73,6 +73,7 @@ sub options {
>   	is_mountpoint => { optional => 1 },
>   	nocow => { optional => 1 },
>   	mkdir => { optional => 1 },
> +	preallocation => { optional => 1 },
>   	# TODO: The new variant of mkdir with  `populate` vs `create`...
>       };
>   }
> diff --git a/PVE/Storage/CIFSPlugin.pm b/PVE/Storage/CIFSPlugin.pm
> index c5f3894..3a7e638 100644
> --- a/PVE/Storage/CIFSPlugin.pm
> +++ b/PVE/Storage/CIFSPlugin.pm
> @@ -142,6 +142,7 @@ sub options {
>   	smbversion => { optional => 1},
>   	mkdir => { optional => 1 },
>   	bwlimit => { optional => 1 },
> +	preallocation => { optional => 1 },
>       };
>   }
>   
> diff --git a/PVE/Storage/DirPlugin.pm b/PVE/Storage/DirPlugin.pm
> index 2267f11..3eeec98 100644
> --- a/PVE/Storage/DirPlugin.pm
> +++ b/PVE/Storage/DirPlugin.pm
> @@ -59,6 +59,7 @@ sub options {
>   	mkdir => { optional => 1 },
>   	is_mountpoint => { optional => 1 },
>   	bwlimit => { optional => 1 },
> +	preallocation => { optional => 1 },
>      };
>   }
>   
> diff --git a/PVE/Storage/GlusterfsPlugin.pm b/PVE/Storage/GlusterfsPlugin.pm
> index ea4df82..d8d2b88 100644
> --- a/PVE/Storage/GlusterfsPlugin.pm
> +++ b/PVE/Storage/GlusterfsPlugin.pm
> @@ -137,6 +137,7 @@ sub options {
>   	format => { optional => 1 },
>   	mkdir => { optional => 1 },
>   	bwlimit => { optional => 1 },
> +	preallocation => { optional => 1 },
>       };
>   }
>   
> @@ -260,7 +261,8 @@ sub alloc_image {
>   
>       my $cmd = ['/usr/bin/qemu-img', 'create'];
>   
> -    push @$cmd, '-o', 'preallocation=metadata' if $fmt eq 'qcow2';
> +    my $prealloc_opt = PVE::Storage::Plugin::preallocation_cmd_option($scfg, $fmt);
> +    push @$cmd, '-o', $prealloc_opt if defined($prealloc_opt);
>   
>       push @$cmd, '-f', $fmt, $volumepath, "${size}K";
>   
> diff --git a/PVE/Storage/NFSPlugin.pm b/PVE/Storage/NFSPlugin.pm
> index 39bf15a..21b288a 100644
> --- a/PVE/Storage/NFSPlugin.pm
> +++ b/PVE/Storage/NFSPlugin.pm
> @@ -90,6 +90,7 @@ sub options {
>   	format => { optional => 1 },
>   	mkdir => { optional => 1 },
>   	bwlimit => { optional => 1 },
> +	preallocation => { optional => 1 },
>       };
>   }
>   
> diff --git a/PVE/Storage/Plugin.pm b/PVE/Storage/Plugin.pm
> index 417d1fd..4308522 100644
> --- a/PVE/Storage/Plugin.pm
> +++ b/PVE/Storage/Plugin.pm
> @@ -41,6 +41,19 @@ our @SHARED_STORAGE = (
>       'pbs',
>   );
>   
> +our $QCOW2_PREALLOCATION = {
> +    off => 1,
> +    metadata => 1,
> +    falloc => 1,
> +    full => 1,
> +};
> +
> +our $RAW_PREALLOCATION = {
> +    off => 1,
> +    falloc => 1,
> +    full => 1,
> +};
> +
>   our $MAX_VOLUMES_PER_GUEST = 1024;
>   
>   cfs_register_file ('storage.cfg',
> @@ -152,6 +165,13 @@ my $defaultData = {
>   	    type => 'string', format => 'pve-storage-format',
>   	    optional => 1,
>   	},
> +	preallocation => {
> +	    description => "Preallocation mode for raw and qcow2 images. " .
> +		"Using 'metadata' on raw images results in preallocation=off.",
> +	    type => 'string', enum => ['off', 'metadata', 'falloc', 'full'],
> +	    default => 'metadata',
> +	    optional => 1,
> +	},
>       },
>   };
>   
> @@ -444,6 +464,31 @@ sub parse_config {
>       return $cfg;
>   }
>   
> +sub preallocation_cmd_option {
> +    my ($scfg, $fmt) = @_;
> +
> +    my $prealloc = $scfg->{preallocation};
> +
> +    if ($fmt eq 'qcow2') {
> +	$prealloc = $prealloc // 'metadata';
> +
> +	die "preallocation mode '$prealloc' not supported by format '$fmt'\n"
> +	    if !$QCOW2_PREALLOCATION->{$prealloc};
> +
> +	return "preallocation=$prealloc";
> +    } elsif ($fmt eq 'raw') {
> +	$prealloc = $prealloc // 'off';
> +	$prealloc = 'off' if $prealloc eq 'metadata';
> +
> +	die "preallocation mode '$prealloc' not supported by format '$fmt'\n"
> +	    if !$RAW_PREALLOCATION->{$prealloc};
> +
> +	return "preallocation=$prealloc";
> +    }
> +
> +    return;
> +}
> +
>   # Storage implementation
>   
>   # called during addition of storage (before the new storage config got written)
> @@ -764,7 +809,8 @@ sub alloc_image {
>       } else {
>   	my $cmd = ['/usr/bin/qemu-img', 'create'];
>   
> -	push @$cmd, '-o', 'preallocation=metadata' if $fmt eq 'qcow2';
> +	my $prealloc_opt = preallocation_cmd_option($scfg, $fmt);
> +	push @$cmd, '-o', $prealloc_opt if defined($prealloc_opt);
>   
>   	push @$cmd, '-f', $fmt, $path, "${size}K";
>   
>