linux-kernel - Re: [PATCH v2] ceph: fix posix ACL hooks

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Message-ID: <CA+55aFz3PyyCqOLs_SBRS3cbGxWd5ez4Svz2+xK+4KtCez8iGw@mail.gmail.com>
Date:	Mon, 3 Feb 2014 14:12:00 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Ilya Dryomov <ilya.dryomov@...tank.com>,
	Sage Weil <sage@...tank.com>, Dave Jones <davej@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	ceph-devel@...r.kernel.org,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Guangliang Zhao <lucienchao@...il.com>,
	Li Wang <li.wang@...ntykylin.com>, zheng.z.yan@...el.com
Subject: Re: [PATCH v2] ceph: fix posix ACL hooks

On Mon, Feb 3, 2014 at 1:59 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
> On Mon, Feb 03, 2014 at 01:03:32PM -0800, Linus Torvalds wrote:
>
>> -     err = vfs_mkdir(path.dentry->d_inode, dentry, mode);
>> +     err = vfs_mkdir(path.dentry, dentry, mode);
>
> Pointless - path.dentry == dentry->d_parent anyway.

Heh. It's no less redundant than it used to be.

But if you want to clean up the vfs_xyzzy() ones further, I'm
perfectly fine with that.

>> -     err = ll_vfs_rename(dir->d_inode, dchild_old, mnt,
>> -                         dir->d_inode, dchild_new, mnt, NULL);
>> +     err = ll_vfs_rename(dir, dchild_old, mnt,
>> +                         dir, dchild_new, mnt, NULL);
>
>
> ... and again, that's completely pointless.

Minimal patch.. I really didn't want to check what the heck lustre
does with the insane ll_vfs thing.

>> -int afs_permission(struct inode *inode, int mask)
>> +int afs_permission(struct dentry *dentry, struct inode *inode, int mask)
>
> Oh, _lovely_.  So not only do we pass dentry, the arguments are redundant
> as well.

Note that *not* passing in inode would make the patch much bigger,
because now every filesystem would have to add the

       struct inode *inode = dentry->d_inode;

at the top.

Also, I'm not actually convinced it is redundant at all. Remember the
RCU lookup case? dentry->d_inode is not safe.

The RCU case actually does

  inode_permission(nd->path.dentry, nd->inode, ..)

and here the difference between nd->inode and dentry->d_inode are
relevant, I think.

>> +static int gfs2_vfs_permission(struct dentry *dentry, struct inode *inode, int mask)
>> +{
>> +     return gfs2_permission(inode, mask);
>> +}
>
> Er...  You do realize that callers of gfs2_permission() tend to have
> the dentry in question, either directly or as ->d_parent of something
> they have?

Not true. Look closer.

Look at gfs2_lookupi() in particular, and check how it is called.

I did hate that part of the patch, and I did mention the kinds of
problems this will cause if the next phase passes in dentry to
"generic_permission()".

                Linus
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