From: Miklos Szeredi <mszeredi@redhat.com>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel <linux-fsdevel@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
David Howells <dhowells@redhat.com>,
Tyler Hicks <tyhicks@canonical.com>
Subject: Re: [PATCH 00/17] clean up readlinks
Date: Tue, 27 Sep 2016 11:38:33 +0200 [thread overview]
Message-ID: <CAOssrKdM2fzKypNJ-b+7wdyp4ZJ9t8hE1_8brKVg5WCTZ-TbOA@mail.gmail.com> (raw)
In-Reply-To: <20160927031019.GF19539@ZenIV.linux.org.uk>
On Tue, Sep 27, 2016 at 5:10 AM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Mon, Sep 12, 2016 at 09:29:02PM +0200, Miklos Szeredi wrote:
>> The first patch is actually a bug fix, but I put it into this bunch for
>> simplicity...
>>
>> The rest are really cleanups as well as minor bugfixes that are byproducts
>> of the cleanups.
>>
>> This series builds on the fact that i_op.readlink is already set to
>> generic_readlink() in 43/50 of the cases. And of those 7 only 4 are doing
>> something special. So more than 90% of readlinks are/could actually just
>> call back into get_link.
>>
>> The interesting cases are:
>>
>> - AFS, which has readlink but not get_link
>> - proc, that allow jumping while following symlinks
>>
>> The first is handled by setting IOP_NOFOLLOW on the inode by the fs.
>>
>> The second one is handled by introducing is_following_link() which returns
>> a bool depending on whether current->nameidata is NULL or not. If it
>> returns false ->get_link() should behave as ->readlink() did. Otherwise it
>> should behave as id did previously.
>>
>> Builds and boots. Can even read symlinks.
>
> I have no problem with "let's get rid of generic_readlink" - not that
> it bought us much, but sure, if you want to have decision made based upon
> the combination of flags, let's do it. Just make NULL ->readlink + non-NULL
> ->get_link() mean generic_readlink(), and we are done.
Indeed. Except it really should be the other way round:
- .get_link always returning the symlink body
- only proc setting .jump_link to do its thing
- RIP .readlink
But that's an extra branch in the symlink following. I was worried
about that and hence gone for the unification of the two.
>
> Overloading ->get_link() for procfs-style ones is just plain wrong,
> though. Your current->nameidata != NULL thing is bloody brittle - what
> happens if some code triggers those readlinks when called by something
> during pathname resolution? Sure, right now existing callers won't.
> But it doesn't take much to grow such a place _and_ have the implications
> go unnoticed for quite a while.
Yeah. We can do your above suggestion, it's certainly less brittle.
But I think it's rather confusing, having ->get_link normally do
readlink, except for proc, where readlink is done by ->readlink.
Thanks,
Miklos
next prev parent reply other threads:[~2016-09-27 9:38 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-12 19:29 [PATCH 00/17] clean up readlinks Miklos Szeredi
2016-09-12 19:29 ` [PATCH 01/17] bad_inode: add missing i_op initializers Miklos Szeredi
2016-09-12 19:29 ` [PATCH 02/17] ovl: use generic_readlink Miklos Szeredi
2016-09-12 19:29 ` [PATCH 03/17] proc/self: " Miklos Szeredi
2016-09-12 19:29 ` [PATCH 04/17] afs: " Miklos Szeredi
2016-09-12 19:29 ` [PATCH 05/17] bad_inode: " Miklos Szeredi
2016-09-12 19:29 ` [PATCH 06/17] vfs: remove page_readlink() Miklos Szeredi
2016-09-12 19:29 ` [PATCH 07/17] vfs: add is_following_link() helper Miklos Szeredi
2016-09-12 19:29 ` [PATCH 08/17] proc: merge proc_pid_readlink() into proc_pid_get_link() Miklos Szeredi
2016-09-12 19:29 ` [PATCH 09/17] proc: merge proc_ns_readlink() into proc_ns_get_link() Miklos Szeredi
2016-09-12 19:29 ` [PATCH 10/17] nsfs: clean up ns_get_name() interface Miklos Szeredi
2016-09-12 19:29 ` [PATCH 11/17] vfs: replace calling i_op->readlink with vfs_readlink() Miklos Szeredi
2016-09-12 19:29 ` [PATCH 12/17] vfs: remove ".readlink = generic_readlink" assignments Miklos Szeredi
2016-09-12 19:29 ` [PATCH 13/17] vfs: remove unused i_op->readlink Miklos Szeredi
2016-09-12 19:29 ` [PATCH 14/17] vfs: remove unused generic_readlink() Miklos Szeredi
2016-09-12 19:29 ` [PATCH 15/17] vfs: add vfs_get_link() helper Miklos Szeredi
2016-09-12 19:29 ` [PATCH 16/17] ovl: use vfs_get_link() Miklos Szeredi
2016-09-12 19:29 ` [PATCH 17/17] ecryptfs: " Miklos Szeredi
2016-09-27 3:10 ` [PATCH 00/17] clean up readlinks Al Viro
2016-09-27 9:38 ` Miklos Szeredi [this message]
2016-09-28 2:17 ` Al Viro
2016-09-28 14:47 ` Miklos Szeredi
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