linux-ext4 - Re: [PATCH v9 0/4] Prepare for upcoming Casefolding/Encryption patches

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Date:   Tue, 23 Jun 2020 22:34:58 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Daniel Rosenberg <drosen@...gle.com>
Cc:     Theodore Ts'o <tytso@....edu>, linux-ext4@...r.kernel.org,
        Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-fscrypt@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Richard Weinberger <richard@....at>,
        linux-mtd@...ts.infradead.org,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        kernel-team@...roid.com
Subject: Re: [PATCH v9 0/4] Prepare for upcoming Casefolding/Encryption
 patches

On Tue, Jun 23, 2020 at 09:33:37PM -0700, Daniel Rosenberg wrote:
> This lays the ground work for enabling casefolding and encryption at the
> same time for ext4 and f2fs. A future set of patches will enable that
> functionality. These unify the highly similar dentry_operations that ext4
> and f2fs both use for casefolding.

I think this undersells this patchset a bit.  This patchset makes ext4 and f2fs
share the casefolded ->d_compare() and ->d_hash() implementations, which
eliminates duplicated code.  That's a good thing regardless of whether we're
going to add encrypt+casefold support or not.

It also changes the casefolded ->d_hash() implementation to not have to allocate
memory (with GFP_ATOMIC, no less), which was a big problem with the old
implementation as it's unreliable and inefficient.

So yes, this prepares for supporting encrypt+casefold.  But these changes make
sense on their own too as an improvement of the casefold feature.  Except for
the one line of code in needs_casefold() that is specific to encrypt+casefold;
maybe that should be left out for now.

(Side note: I think you could drop linux-doc and linux-mtd from Cc, as this
patchset isn't really relevant to those mailing lists.)

- Eric