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Re: [Libguestfs] [PATCH] NEW API: add blkid command to print the attributes of the device



On 12/03/2011 03:28 PM, Richard W.M. Jones wrote:

> On Sat, Dec 03, 2011 at 12:34:06PM +0800, Wanlong Gao wrote:
>> A NEW API blkid.
>> It can print the device attributes.
>> Use it after list-devices, we can list ower devices and the attributes
>> of each device.
>> Use it like:
>> blkid <device>
>> It's should be a usefull function, and needed no test case for it.
> 
> Yes, in principle.
> 
> However it certainly _does_ need a test, in case the blkid command
> breaks or changes in future.
> 
> Further comments on the patch below.
> 
>> Signed-off-by: Wanlong Gao <gaowanlong cn fujitsu com>
>> ---
>>  daemon/blkid.c                 |   75 ++++++++++++++++++++++++++++++++++++++++
>>  generator/generator_actions.ml |   73 ++++++++++++++++++++++++++++++++++++++
>>  src/MAX_PROC_NR                |    2 +-
>>  3 files changed, 149 insertions(+), 1 deletions(-)
>>
>> diff --git a/daemon/blkid.c b/daemon/blkid.c
>> index 6d395c1..a7fd6bc 100644
>> --- a/daemon/blkid.c
>> +++ b/daemon/blkid.c
>> @@ -83,3 +83,78 @@ do_vfs_uuid (const char *device)
>>  {
>>    return get_blkid_tag (device, "UUID");
>>  }
>> +
>> +char **
>> +do_blkid(const char *device)
>> +{
>> +  int r;
>> +  char *out = NULL, *err = NULL;
>> +  char **lines = NULL;
>> +
>> +  char **ret = NULL;
>> +  int size = 0, alloc = 0;
>> +
>> +  const char *blkid[] = {"blkid", "-p", "-i", "-o", "export", device, NULL};
>> +  r = commandv(&out, &err, blkid);
>> +  if (r == -1) {
>> +    reply_with_error("%s", err);
>> +    goto error;
>> +  }
>> +
>> +  /* Split the command output into lines */
>> +  lines = split_lines(out);
>> +  if (lines == NULL) {
>> +    reply_with_perror("malloc");
>> +    goto error;
>> +  }
>> +
>> +  /* Parse the output of blkid -p -i -o export:
>> +   * UUID=b6d83437-c6b4-4bf0-8381-ef3fc3578590
>> +   * VERSION=1.0
>> +   * TYPE=ext2
>> +   * USAGE=filesystem
>> +   * MINIMUM_IO_SIZE=512
>> +   * PHYSICAL_SECTOR_SIZE=512
>> +   * LOGICAL_SECTOR_SIZE=512
>> +   * PART_ENTRY_SCHEME=dos
>> +   * PART_ENTRY_TYPE=0x83
>> +   * PART_ENTRY_NUMBER=6
>> +   * PART_ENTRY_OFFSET=642875153
>> +   * PART_ENTRY_SIZE=104857600
>> +   * PART_ENTRY_DISK=8:0
>> +   */
>> +  for (char **i = lines; *i != NULL; i++) {
>> +    char *line = *i;
>> +
>> +    /* Skip blank lines (shouldn't happen) */
>> +    if (line[0] == '\0') continue;
>> +
>> +    /* Split the line in 2 at the equals sign */
>> +    char *eq = strchr(line, '=');
>> +    if (eq) {
>> +      *eq = '\0'; eq++;
>> +
>> +      /* Add the key/value pair to the output */
>> +      if (add_string(&ret, &size, &alloc, line) == -1 ||
>> +          add_string(&ret, &size, &alloc, eq) == -1) goto error;
>> +    } else {
>> +      fprintf(stderr, "blkid: unexpected blkid output ignored: %s", line);
>> +    }
>> +  }
>> +
>> +  free(out);
>> +  free(err);
>> +  free(lines);
>> +
>> +  if (add_string(&ret, &size, &alloc, NULL) == -1) return NULL;
>> +
>> +  return ret;
>> +
>> +error:
>> +  free(out);
>> +  free(err);
>> +  if (lines) free(lines);
>> +  if (ret) free_strings(ret);
>> +
>> +  return NULL;
>> +}
>> diff --git a/generator/generator_actions.ml b/generator/generator_actions.ml
>> index 0e39e2f..d624f9b 100644
>> --- a/generator/generator_actions.ml
>> +++ b/generator/generator_actions.ml
>> @@ -6538,6 +6538,79 @@ The name of the MD device.
>>  This command deactivates the MD array named C<md>.  The
>>  device is stopped, but it is not destroyed or zeroed.");
>>  
>> +  ("blkid", (RHashtable "info", [Device "device"], []), 303, [],
>> +   [],
>> +   "print block device attributes",
>> +   "\
>> +This command exposes the output of 'blkid -p -i -o export <device>'. The following
> 
> Don't describe how the command is implemented -- we may change the
> implementation in future.  Be less specific, such as "This command
> returns block device attributes for C<device>".  Also remember this is
> POD documentation, so you can't use "<" and ">" characters without
> escaping them.


got it.

> 
>> +C<device> should be a block device or patition, for example C</dev/sda> or C</dev/sdb1>.
> 
> This example is unnecessary -- using Device ensures that users have to
> pass a device name here.


got it.

> 
>> +=over
>> +
>> +=item C<UUID>
>> +
>> +The uuid of this device.
>> +
>> +=item C<UUID_SUB>
>> +
>> +The sub uuid of this device.
>> +
>> +=item C<LABEL>
>> +
>> +The label of this device.
>> +
>> +=item C<VERSION>
>> +
>> +The version of blkid command.
>> +
>> +=item C<TYPE>
>> +
>> +The filesystem type or RAID of this device.
>> +
>> +=item C<USAGE>
>> +
>> +The usage of this device, for example C<filesystem> or C<raid>.
>> +
>> +=item C<MINIMUM_IO_SIZE>
>> +
>> +The minimum io size of this device.
>> +
>> +=item C<PHYSICAL_SECTOR_SIZE>
>> +
>> +The pyhsical sector size of this device.
>> +
>> +=item C<LOGICAL_SECTOR_SIZE>
>> +
>> +The logical sector size of this device.
>> +
>> +=item C<PART_ENTRY_SCHEME>
>> +
>> +The scheme entry of this partition(only presented when it's a partition).
> 
> ^^ Add a space.


got it. will fix.

> 
> [...]
> 
> How many of these fields does blkid define?  Are they likely to change
> in future?  If we promise that fields are returned then we have to
> stick to that promise in future because of libguestfs ABI commitments.
> It's better to promise fewer fields, and only ones that we could
> implement by hand if blkid disappeared in future.


will do.

> 
> This also needs a test -- see "tune2fs" in generator/generator_actions.ml
> for an example using TestOutputHashtable.


Yeah, will look into, thanks a lot.

> 
> Rich.
> 



-Wanlong Gao


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