Re: [PATCH] btrfs-progs: Add mount point output for 'btrfs fi df' command.

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

-------- Original Message --------
Subject: Re: [PATCH] btrfs-progs: Add mount point output for 'btrfs fi 
df' command.
From: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
To: Qu Wenruo <quwenruo@cn.fujitsu.com>, linux-btrfs@vger.kernel.org
Date: 2014年07月10日 08:41
> Hi Qu,
>
> (2014/07/08 14:43), Qu Wenruo wrote:
>> Add mount point output for 'btrfs fi df'.
>> Also since the patch uses find_mount_root() to find mount point,
>> now 'btrfs fi df' can output more meaningful error message when given a
>> non-btrfs path.
>>
>> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
>> ---
>> This patch needs to be merged after the following path:
>> btrfs-progs: Check fstype in find_mount_root()
>> ---
>>    cmds-filesystem.c | 10 ++++++++++
>>    1 file changed, 10 insertions(+)
>>
>> diff --git a/cmds-filesystem.c b/cmds-filesystem.c
>> index 4b2d27e..d571765 100644
>> --- a/cmds-filesystem.c
>> +++ b/cmds-filesystem.c
>> @@ -187,12 +187,22 @@ static int cmd_filesystem_df(int argc, char **argv)
>>           int ret;
>>           int fd;
>>           char *path;
>> +       char *mount_point = NULL;
>>           DIR *dirstream = NULL;
>>    
>>           if (check_argc_exact(argc, 2))
>>                   usage(cmd_filesystem_df_usage);
>>    
>>           path = argv[1];
>> +       ret = find_mount_root(path, &mount_point);
>> +       if (ret < 0) {
>> +	       if (ret != -ENOENT)
> Is "if (ret != -ENOENT)" to avoid the error message duplication
> with the following code?
Yes.
>
> utils.c:
> ===============================================================================
> ...
> int find_mount_root(...)
> {
> 	...
>          if (!longest_match) {
>                  fprintf(stderr,
>                          "ERROR: Failed to find mount root for path %s.\n",
>                          path);
>                  return -ENOENT;
>          }
> ...
> ===============================================================================
>
> I consider making the following two patches is the better way.
>
>   - Patch 1. Removing this error message from find_mount_root().
>              This cause no problem since all the current find_mount_root()
>              caller show their own error message.
>              
>   - Patch 2. Your patch with removing that if sentence.
Thanks for the suggestion, it really makes sense.
I'll send the new version with other small modification like integrate 
realpath() into find_mount_root()
since every caller of find_mount_root() does the realpath resolve.

Thanks,
Qu
>
> Thanks,
> Satoru
>
>> +		       fprintf(stderr, "ERROR: Failed to find mount root for path %s: %s\n",
>> +			       path, strerror(-ret));
>> +		return 1;
>> +       }
>> +       printf("Mounted on: %s\n", mount_point);
>> +       free(mount_point);
>>    
>>           fd = open_file_or_dir(path, &dirstream);
>>           if (fd < 0) {
>>