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From:   Gabriel Krisman Bertazi <krisman@collabora.com>
To:     Eric Biggers <ebiggers@kernel.org>
Cc:     Slava Bacherikov <slava@bacher09.org>, tytso@mit.edu,
        linux-ext4@vger.kernel.org
Subject: Re: [PATCH v2] tune2fs: allow disabling casefold feature
Organization: Collabora
References: <YscmTC3Mk9OXqOgL@gmail.com>
        <20220707190456.64972-1-slava@bacher09.org>
        <Ysc5HYPXUs6rW02S@gmail.com>
Date:   Thu, 07 Jul 2022 16:16:21 -0400
In-Reply-To: <Ysc5HYPXUs6rW02S@gmail.com> (Eric Biggers's message of "Thu, 7
        Jul 2022 19:50:53 +0000")
Message-ID: <87tu7s3ch6.fsf@collabora.com>
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Eric Biggers <ebiggers@kernel.org> writes:

> On Thu, Jul 07, 2022 at 10:04:56PM +0300, Slava Bacherikov wrote:
>> +	if (FEATURE_OFF(E2P_FEATURE_INCOMPAT, EXT4_FEATURE_INCOMPAT_CASEFOLD)) {
>> +		if (mount_flags & EXT2_MF_MOUNTED) {
>> +			fputs(_("The casefold feature may only be disabled when "
>> +				"the filesystem is unmounted.\n"), stderr);
>> +			return 1;
>> +		}
>> +		if (has_casefold_inode(fs)) {
>> +			fputs(_("The casefold feature couldn't be disabled when "
>> +					"there are inodes with +F flag.\n"), stderr);
>> +			return 1;
>> +		}
>> +		enabling_casefold = 0;
>
> Likewise, "couldn't" => "can't".
>
> Also, what are the semantics of disabling casefold, exactly?  Do the encoding
> and encoding flags fields in the superblock also get cleared?

The kernel is able to ignore the non-zero encoding field if the feature
is not set, but we definitely don't want to rely on that.  The patch
should explicitly zero both s_encoding and s_encoding_flags.

-- 
Gabriel Krisman Bertazi