[RFC] Move all btrfs command to only one command

From: Goffredo Baroncelli <kreijack@gmail.com>
To: linux-btrfs@vger.kernel.org
Cc: David Nicol <davidnicol@gmail.com>, taruishi.hiroak@jp.fujitsu.com
Subject: [RFC] Move all btrfs command to only one command
Date: Thu, 21 Jan 2010 20:29:26 +0100	[thread overview]
Message-ID: <201001212029.26681.kreijack@libero.it> (raw)

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Hi all

this RFC is about unify all btrfs command (btrfsctl, btrfs-show, btrfs-tune.. 
) in only one called "btrfs" (or whatever we want).

Today "btrfsctl" needs a "bit" of care because
  * the help is basically wrong [1]
  * the return codes are incoherent [2]
  * the syntax of the command are very ugly (a lot of people complained 
    about the subvolumes/snapshot creation, because they aren't very clear)
    [3]
  * the code is a mess (in the main there is a useless for(); there a lot
    of 'if' because sometime the last argument is the target of ioctl,
    sometime no..) [4]
  * The checks of the number of argument are incorrect [5]

I think that is better to rewrite from scratch a new command instead of 
patching the old one. So we don't care about the backward compatibility.

Other filesystem (hammer, tux3, zfs) have only one command for management 
purpose. Instead we have btrfsctl (which has a lot of different
function) and btrfs-show, btrfs-tune, btrfs-volume which have few functions.

There are patches which address [6] some of the previous issues, 
but these are not integrated (because the developers are busy on other 
issues). To me rewriting from scratch seems a fast path for solving these 
issues.

I made a prototype (see attached file) in bash of what "btrfs" should be. The 
major different from btrfsctl are:
- I talk about clone and not snapshot
- If a sub-volume is required (for example for the cloning), the program check 
that the argument is a root of the subvolume and not a subdirectory
- Creating a sub-volume requires only one argument 

Below some examples:

$ btrfs                         
Usage:                                              
        btrfs clone|-c <source> [<dest>/]<name>     
                Clone the subvolume <source> with the name <name> in the 
<dest>
                directory.                                                     
        btrfs delete|-d <subvolume>                                            
                Delete the subvolume <subvolume>.                              
        btrfs create|-C [<dest>/]<name>
                Create a subvolume in <dest> (or the current directory if not
                passed.
        btrfs defrag|-d <file>|<dir> [<file>|<dir>...]
                Defragment a file or a directory.
        btrfs fssync|-s <path>
                Force a fs sync on the filesystem <path>
        btrfs resize|-r [+/-]<newsize>[gkm]|max <filesystem>
                Resize the file system. If 'max' is passed, the filesystem
                will occupe all available space on the device.
        btrfs scan|-S [<device> [<device>..]
                Scan all device for or the passed device for a btrfs 
filesystem.
        btrfs show|-l <dev>|<label> [<dev>|<label>.. ]
                Show the btrfs devices
        btrfs balance|-b <path>
                Balance teh chunk across the device
        btrfs add|-A <dev> <path>
                Add a device to a filesystem
        btrfs rem|-R <dev> <path>
                Remove a device to a filesystem

        btrfs help|--help|-h
                Show the help.

Comment are welcome

[1] In the help the -r, -c options seem that don't need any further argument; 
The -D command seems that accpet only "." as 2nd parameter....

[2] If something goes wrong btrfsctl returns 1; if the ioctl return 0 the 
command still returns 1...

[3] See the email in the mailing list

[4] If I does
   btrfsctl -c -d -A -S a .
what result do you aspect ?

[5] If I pass more argument than the ones needed no error is showed. -D checks 
if there is only one argument, when it needs two argument...

[6] 
- 10/26/09 - little fixme in btrfsctl.c [PATCH] - From: 
David Nicol <davidnicol@gmail.com>
- 12/24/09 - [PATCH] btrfs-progs: check slash in deleting subvolumes. - From: 
TARUISI 
- 12/13/09 - [PATCH] Improve the btrfsctl help - From: 
Goffredo Baroncelli <kreijack@gmail.com>

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