linux-kernel - Re: [PATCH 04/79] ext4: split inode_operations for encrypted symlinks off the rest

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Date:	Tue, 5 May 2015 08:01:52 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Neil Brown <neilb@...e.de>, Christoph Hellwig <hch@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH 04/79] ext4: split inode_operations for encrypted symlinks
 off the rest

On Mon, May 4, 2015 at 10:21 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
>         } else if (S_ISLNK(inode->i_mode)) {
> -               if (ext4_inode_is_fast_symlink(inode) &&
> -                   !ext4_encrypted_inode(inode)) {
> +               if (ext4_encrypted_inode(inode)) {
> +#ifdef CONFIG_EXT4_FS_ENCRYPTION
> +                       inode->i_op = &ext4_encrypted_symlink_inode_operations;
> +                       ext4_set_aops(inode);
> +#else
> +                       BUILD_BUG();
> +#endif
> +               } else if (ext4_inode_is_fast_symlink(inode)) {
>                         inode->i_op = &ext4_fast_symlink_inode_operations;
>                         nd_terminate_link(ei->i_data, inode->i_size,
>                                 sizeof(ei->i_data) - 1);

Ugh. Could we aim to *not* add code like this.

Instead, just declare (but don't define) the
ext4_encrypted_symlink_inode_operations thing, so that *if* somebody
uses it they get a link error, and make sure that
"ext4_encrypted_inode()" ends up always returning zero when encryption
isn't enabled, so that the compiler will actually optimize the whole
thing out (which apparently is already the case, judging by the
build-bug-on.

I really prefer to not see #ifdef's inside the middle of anything but
trivial helper functions. I know we have them, and I wish we didn't,
but at least we can aim to not add more of them.

                         Linus
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