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

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Message-ID: <CA+55aFwTuBDHgQoTymr8OtE-+k=+pX0T_eb+fff0K+Pa3C-g-Q@mail.gmail.com>
Date:	Wed, 29 Jan 2014 11:09:18 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ilya Dryomov <ilya.dryomov@...tank.com>
Cc:	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>,
	Christoph Hellwig <hch@...radead.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	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 Wed, Jan 29, 2014 at 8:37 AM, Ilya Dryomov <ilya.dryomov@...tank.com> wrote:
> From: Sage Weil <sage@...tank.com>
>
> The merge of 7221fe4c2 raced with upstream changes in the generic POSIX
> ACL code (2aeccbe95).  Update Ceph to use the new helpers as well by
> dropping the now-generic functions and setting the set_acl inode op.
>
> Signed-off-by: Sage Weil <sage@...tank.com>

Ok, I already committed my untested (and broken) patch yesterday,
because even a broken tree is better than a non-*compiling* tree for
testing.

I created a diff from my current tree to this, and will happily apply
it, but the sign-off chain is now broken (Ilya didn't sign off on his
changes to Sage's patch. Not that it really matters for what is really
a one-liner change, but I thought I'd mention it, since another issue
came up with this patch..

Ceph now does

        struct dentry *dentry = d_find_alias(inode);

in its ceph_set_acl() function, and that's because the VFS layer
doesn't pass down the dentry to the acl code any more.

Christoph - that sounds like a misfeature in the new interfaces. I
realize that for traditional unix filesystems, the path is irrelevant
for an inode operation, but the thing is, from a Linux VFS standpoint
and a conceptual standpoint, the dentry really is the more important
and unique one, and some filesystems want the dentry because they are
*correctly* designed to be about pathnames.

Network filesystems that are pass file descriptors around (ie NFS etc)
are not the "RightWay(tm)" of doing things, so I think that it is
quite reasonable for ceph to want the *path* to the inode and not just
the inode.

So attached is the incremental diff of the patch by Sage and Ilya, and
I'll apply it (delayed a bit to see if I can get the sign-off from
Ilya), but I also think we should fix the (non-cached) ACL functions
that call down to the filesystem layer to also get the dentry.

We already do that for the xattr functions, just not for
get_acl()/set_acl()/acl_chmod().

Christoph, Al? Yes, most filesystems will ignore the dentry pointer, but still..

               Linus

View attachment "patch.diff" of type "text/plain" (3479 bytes)