[stgt] [PATCH 1/2] TGTIMG add a new --thin-provisioning flag when creating disk devices

[FUJITA Tomonori]

On Sat, 31 Mar 2012 14:24:22 +1100
ronnie sahlberg <ronniesahlberg at gmail.com> wrote:

> From fc6859e6ab9dea7bbf71a8f411519dbf5f02f0ef Mon Sep 17 00:00:00 2001
> From: Ronnie Sahlberg <ronniesahlberg at gmail.com>
> Date: Fri, 30 Mar 2012 16:46:38 +1100
> Subject: [PATCH 1/2] TGTIMG: Add support for thin-provisioning
> 
> A new flag --ting-provisioning is added to the tgtimg command.
> When used this flag will create a sparse file without any
> allocation guarantee.
> It will also verify that FALLOC_FL_PUNCH_HOLE works.
> 
> If such files are created, a future patch to tgtd will add
> support for the UNMAP command that is used by initiators to
> release blocks that are no longer in use.
> 
> Signed-off-by: Ronnie Sahlberg <ronniesahlberg at gmail.com>
> ---
>  doc/tgtimg.8.xml |   22 ++++++++++++++++++++++
>  usr/tgtimg.c     |   45 ++++++++++++++++++++++++++++++++++++---------
>  2 files changed, 58 insertions(+), 9 deletions(-)
> 
> diff --git a/doc/tgtimg.8.xml b/doc/tgtimg.8.xml
> index 5a787af..e067db0 100644
> --- a/doc/tgtimg.8.xml
> +++ b/doc/tgtimg.8.xml
> @@ -21,6 +21,7 @@
>  		<arg choice="opt">-s --size <size></arg>
>  		<arg choice="opt">-t --type <media-type></arg>
>  		<arg choice="opt">-f --file <path></arg>
> +		<arg choice="opt">-T --thin-provisioning</arg>
>  	</cmdsynopsis>
>  	<cmdsynopsis>
>  		<command>tgtimg --help</command>
> @@ -126,6 +127,27 @@ Supported media types for tape devices are :
>          </listitem>
>        </varlistentry>
>  
> +      <varlistentry><term><option>-T, --thin-provisioning</option></term>
> +        <listitem>
> +          <para>
> +	    This argument makes the allocation of the image format use
> +	    thin-provisioning. This means that the file created will be a
> +	    sparse file that will allocate blocks from the filesystem on demand.
> +          </para>
> +          <para>
> +	    Be careful when using thin-provisioning. If the filesystem
> +	    fills up a iSCSI write to a thin-provisioned LUN
> +	    can fail. Initiators generally do not handle "out of space" errors
> +	    gracefully.
> +          </para>
> +          <para>
> +	    Thin-provisioning uses FALLOC_FL_PUNCH_HOLE which is only available
> +	    on some linux filesystems. Thin-provisioning can only be used for
> +	    DISK images.
> +          </para>
> +        </listitem>
> +      </varlistentry>
> +
>      </variablelist>
>    </refsect1>
>  
> diff --git a/usr/tgtimg.c b/usr/tgtimg.c
> index f4388d9..bb417fe 100644
> --- a/usr/tgtimg.c
> +++ b/usr/tgtimg.c
> @@ -1,5 +1,5 @@
>  /*
> - *	Create blank media files for bs_tape backing store
> + *	Create media files for TGTD devices
>   *
>   * Copyright (C) 2008 Mark Harvey markh794 at gmail.com
>   *
> @@ -22,6 +22,7 @@
>  #define _XOPEN_SOURCE 600
>  #include <errno.h>
>  #include <fcntl.h>
> +#include <linux/falloc.h>
>  #include <getopt.h>
>  #include <inttypes.h>
>  #include <stdio.h>
> @@ -59,6 +60,7 @@ struct option const long_options[] = {
>  	{"size", required_argument, NULL, 's'},
>  	{"type", required_argument, NULL, 't'},
>  	{"file", required_argument, NULL, 'f'},
> +	{"thin-provisioning", no_argument, NULL, 'T'},
>  	{NULL, 0, NULL, 0},
>  };
>  
> @@ -71,7 +73,7 @@ static void usage(int status)
>  		printf("\
>  Linux SCSI Target Framework Image File Utility, version %s\n\
>  \n\
> -  --op new --device-type tape --barcode=[code] --size=[size] --type=[type] --file=[path]\n\
> +  --op new --device-type tape --barcode=[code] --size=[size] --type=[type] --file=[path] [--thin-provisioning]\n\
>  			create a new tape image file.\n\
>  			[code] is a string of chars.\n\
>  			[size] is media size(in megabytes).\n\
> @@ -83,6 +85,7 @@ Linux SCSI Target Framework Image File Utility, version %s\n\
>    --op show --device-type tape --file=[path]\n\
>  			dump the tape image file contents.\n\
>  			[path] is the tape image file\n\
> +  --thin-provisioning   create a sparse file for the media\n\
>    --help                display this help and exit\n\
>  \n\
>  Report bugs to <stgt at vger.kernel.org>.\n", TGT_VERSION);
> @@ -414,7 +417,7 @@ static int mmc_ops(int op, char *path, char *media_type)
>  	return 0;
>  }
>  
> -static int sbc_new(int op, char *path, char *capacity, char *media_type)
> +static int sbc_new(int op, char *path, char *capacity, char *media_type, int thin)
>  {
>  	int fd;
>  
> @@ -438,9 +441,29 @@ static int sbc_new(int op, char *path, char *capacity, char *media_type)
>  			perror("Failed creating file");
>  			exit(2);
>  		}
> -		if (posix_fallocate(fd, 0, size*1024*1024LL) == -1) {
> -			perror("posix_fallocate failed.");
> -			exit(3);
> +		if (thin) {
> +#ifdef FALLOC_FL_PUNCH_HOLE
> +			if (ftruncate(fd, size*1024*1024LL) != 0) {
> +				perror("Failed to set file size");
> +				exit(6);
> +			}
> +			if (fallocate(fd,
> +				FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
> +				0, size*1024*1024LL) != 0) {
> +				perror("Thin provisioning not available on"
> +					" this file");
> +				exit(5);
> +			}
> +#else
> +			perror("This version of tgtimg is not compiled "
> +				"with thin-provisioning support.");
> +			exit(6);
> +#endif

Great, I tried to find the time to implement this feature.

We avoid using ifdef in *.c. Can you create a helper function for
discard stuff in util.h? I guess the function can be used in both
patches.
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