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Subject: Re: [PATCH -V1 22/22] ext4: Add Ext4 compat richacl feature flag
From: Andreas Dilger <adilger@dilger.ca>
In-Reply-To: <877g65biu4.fsf@linux.vnet.ibm.com>
Date: Thu, 1 May 2014 11:52:48 -0600
Cc: agruen@kernel.org, bfields@fieldses.org, akpm@linux-foundation.org,
        viro@zeniv.linux.org.uk, dhowells@redhat.com,
        linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org,
        linux-kernel@vger.kernel.org
Message-Id: <14876338-8D87-48CD-B8B9-B44F311BB329@dilger.ca>
References: <1398615293-22931-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1398615293-22931-23-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <88FB2DB7-126A-400E-9B44-19E99A553B2B@dilger.ca> <877g65biu4.fsf@linux.vnet.ibm.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Sender: linux-nfs-owner@vger.kernel.org


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On May 1, 2014, at 9:48 AM, Aneesh Kumar K.V =
<aneesh.kumar@linux.vnet.ibm.com> wrote:

> Andreas Dilger <adilger@dilger.ca> writes:
>=20
>> On Apr 27, 2014, at 10:14 AM, Aneesh Kumar K.V =
<aneesh.kumar@linux.vnet.ibm.com> wrote:
>>> This feature flag can be used to enable richacl on
>>> the file system. Once enabled the "acl" mount option
>>> will enable richacl instead of posix acl
>>=20
>>> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
>>> index 6f9e6fadac04..2a0221652d79 100644
>>> --- a/fs/ext4/super.c
>>> +++ b/fs/ext4/super.c
>>> @@ -1274,6 +1274,30 @@ static ext4_fsblk_t get_sb_block(void **data)
>>> 	return sb_block;
>>> }
>>>=20
>>> +static void enable_acl(struct super_block *sb)
>>> +{
>>> +#if !defined(CONFIG_EXT4_FS_POSIX_ACL) && =
!defined(CONFIG_EXT4_FS_RICHACL)
>>> +	return;
>>> +#endif
>>> +	if (EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_RICHACL)) {
>>> +		sb->s_flags |=3D MS_RICHACL;
>>> +		sb->s_flags &=3D ~MS_POSIXACL;
>>> +	} else {
>>> +		sb->s_flags |=3D MS_POSIXACL;
>>> +		sb->s_flags &=3D ~MS_RICHACL;
>>> +	}
>>=20
>> This should put the #ifdef around the code that is being =
enabled/disabled,
>> otherwise it just becomes dead code:
>>=20
>> static int enable_acl(struct super_block *sb)
>> {
>> 	if (EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_RICHACL)) {
>> #if defined(CONFIG_EXT4_FS_RICHACL)
>> 		sb->s_flags |=3D MS_RICHACL;
>> 		sb->s_flags &=3D ~MS_POSIXACL;
>> #else
>> 		return -EOPNOTSUPP;
>> #endif
>> 	} else {
>> #if defined(CONFIG_EXT4_FS_POSIX_ACL)
>> 		sb->s_flags |=3D MS_POSIXACL;
>> 		sb->s_flags &=3D ~MS_RICHACL;
>> #else
>> 		return -EOPNOTSUPP;
>> #endif
>> 	}
>> 	return 0;
>> }
>=20
> That is too much #ifdef with no real benefit ?

The benefit is that if neither CONFIG_EXT4_FS_RICHACL nor =
CONFIG_EXT4_FS_POSIX_ACL are defined there isn't unreachable code
after "return" at the start of the function.  Some static code
analysis tools will complain about this.

Cheers, Andreas


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