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SubjectRe: [GIT PULL] ext4 updates for 4.15
On Tue, Nov 14, 2017 at 4:56 PM, Theodore Ts'o <> wrote:
> The e2fsprogs user space libraries all use
> EXT4_*_FL, and we can't change that without breaking applications
> depending on userspace, but we can keep things consistent in the
> kernel, and that probably means completely converting away from
> EXT4_*_FL, if possible.

So I don't think you'd necessarily need to convert from one to the
other, but wouldn't it be nice if you at least defined one in terms of
the other, ie something like


so that when you grep for one you see how they are directly related.

Now it was much less obvious, and I was nervous because that whole
series did introduce _different_ bits that were not in the same space
at all, and encoded the same thing (ie that S_ENCRYPTED bit).

Maybe this normally doesn't come up, but it was not all that obvious,
particularly since there was a lot of indirection:

ext4_encrypted_inode() ->
ext4_test_inode_flag(inode, EXT4_INODE_ENCRYPT) ->

That EXT4_INODE_BIT_FNS thing was really fascinating to see.

So just confirming that yes,


is the same thing as

EXT4_I(inode)->i_flags & EXT4_ENCRYPT_FL

was a real adventure.

Making it clear that EXT4_ENCRYPT_FL and EXT4_INODE_ENCRYPT are the
same bit would maybe have lessened the confusion at least a tiny bit.

Of course, not having five different ways to test the same bit would
have been even better.

Ok, I'm exaggerating.

But there really does seem to be a lot of different ways to check
i_flags bits, with some uses checking it directly, the places
_setting_ it using ext4_set_inode_flag(), and then other testers using
bit-specific helper.

And that somewhat confusing model seems to be true of pretty much all the bits.

As long as you can keep track of it, I guess it's fine.


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