linux-kernel - Re: [PATCH v18 21/22] ext4: Add richacl support

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Message-ID: <CAHc6FU5f4i_nvwR06Cp7dMJ0AZp2ZuXVrY7cdksLOR3y9P1_rw@mail.gmail.com>
Date:	Wed, 16 Mar 2016 23:38:32 +0100
From:	Andreas Gruenbacher <agruenba@...hat.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Alexander Viro <viro@...iv.linux.org.uk>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
	"Theodore Ts'o" <tytso@....edu>, linux-cifs@...r.kernel.org,
	Linux API <linux-api@...r.kernel.org>,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	LKML <linux-kernel@...r.kernel.org>,
	XFS Developers <xfs@....sgi.com>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Jeff Layton <jlayton@...chiereds.net>,
	linux-ext4 <linux-ext4@...r.kernel.org>,
	Anna Schumaker <anna.schumaker@...app.com>
Subject: Re: [PATCH v18 21/22] ext4: Add richacl support

On Tue, Mar 15, 2016 at 8:17 AM, Christoph Hellwig <hch@...radead.org> wrote:
> On Mon, Mar 14, 2016 at 12:08:31AM +0100, Andreas Gruenbacher wrote:
>> The xattr representation is the same on disk and at the xattr syscall
>> layer, and so richacl_from_xattr is used for converting into the
>> in-memory representation in both cases. The error codes are not the
>> same when a user supplies an invalid value via setxattr or NFS and
>> when an invalid xattr is read from disk though. I'll add a parameter
>> to richacl_from_xattr to make this more explicit.
>
> Better add a wrapper instead of a parameter.
>
>>
>> >> +static int
>> >> +__ext4_set_richacl(handle_t *handle, struct inode *inode, struct richacl *acl)
>> >> +{
>> >> +     const int name_index = EXT4_XATTR_INDEX_RICHACL;
>> >> +     umode_t mode = inode->i_mode;
>> >> +     int retval, size;
>> >> +     void *value;
>> >> +
>> >> +     if (richacl_equiv_mode(acl, &mode) == 0) {
>> >> +             inode->i_ctime = ext4_current_time(inode);
>> >> +             inode->i_mode = mode;
>> >> +             ext4_mark_inode_dirty(handle, inode);
>> >> +             return __ext4_remove_richacl(handle, inode);
>> >> +     }
>> >
>> > Should this check for a NULL acl instead of special casing that
>> > in ext4_set_richacl?
>>
>> I'm not sure I understand what you mean. When the
>
> ext4_set_richacl checks for a NULL acl pointer and then calls into
> __ext4_remove_richacl.  I'd rather have that special casing in one
> place.

Those are two different cases: the first is where ext4_set_richacl is
called with a NULL acl to remove an existing ACL; the second is where
ext4_set_richacl is called with a mode-equivalent ACL to set the mode
and remove any existing ACL.

The check for mode-equivalent ACLs is in __ext4_set_richacl and not in
ext4_set_richacl because an inherited ACL (ext4_init_acl) can also be
mode-equivalent.

Andreas