Re: [PATCH] btrfs-progs: add supported attr flags to btrfs(5)

[Eric Sandeen <sandeen@redhat.com>]

On 6/27/14, 11:10 AM, David Sterba wrote:
> On Fri, Jun 27, 2014 at 10:36:54AM -0500, Eric Sandeen wrote:

...

>> btrfs tries to handle a flag value which is identical to the
>> 'X' flag value, which lsattr/chattr says is readonly...
> 
> I'm looking at it from the kernel side, ie what's its meaning of the
> flag. The chattr tool still lives under the hood of e2fsprogs, but
> the ioctl interface is inherited to other filesystems (stating the
> obvious). e2fsprogs/chattr can decide to implement other meaning or new
> bits more or less freely (eg. there's the new 'N' flag for inlined files
> that I discovered just today while exploring the 'X' flag).

Yes, the interface originated w/ extN, but has clearly spread to other
filesystems, and spread like a weed.  ;)  It's still the de facto
interface, but looking through other filesystems, it's a bit of a disaster.
(filesystems specifying inheritance of flags they ignore, for example).

> There was a discussion at fsdevel about extending the interface or
> reworking it completely, I don't know if there's an outcome.
> 
> From the btrfs side, we have the object properties that make a nice
> interface for accessing the file attributes in parallel with the chattr
> tool. The interface is currently underused so it's not possible to
> manipulate the flags yet.

or test the code, despite it being merged.  \o/  oh well...

> I'd rather move the efforts to finalize this interface than adding
> single bits of the SETFLAGS ioctl and further extensions of the
> chattr/lsattr tools.

ok.  In any case, back to the original patch:  Your changes look fine.
'X' can't be set, so leave it out.  Sorry about the 'd' vs 'D' - and I
like the new formatting.  Feel free to make those changes.

(only nitpick: is 'X' ever reported by lsattr on btrfs?  If so,
it could/should still be included)

((and a side note: I tried to change the text of the manpage to
be "btrfs" not "btrfs-mount" but that somehow broke the build, and
I didn't dig a lot further)) 

-Eric