From: Linus Torvalds <torvalds@linux-foundation.org>
To: Stefan Metzmacher <metze@samba.org>
Cc: David Howells <dhowells@redhat.com>,
Aleksa Sarai <cyphar@cyphar.com>,
Al Viro <viro@zeniv.linux.org.uk>, Ian Kent <raven@themaw.net>,
Miklos Szeredi <mszeredi@redhat.com>,
Christian Brauner <christian@brauner.io>,
Jann Horn <jannh@google.com>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Karel Zak <kzak@redhat.com>,
jlayton@redhat.com, Linux API <linux-api@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
LSM List <linux-security-module@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 01/14] VFS: Add additional RESOLVE_* flags [ver #18]
Date: Thu, 12 Mar 2020 09:24:49 -0700 [thread overview]
Message-ID: <CAHk-=wgu3Wo_xcjXnwski7JZTwQFaMmKD0hoTZ=hqQv3-YojSg@mail.gmail.com> (raw)
In-Reply-To: <3d209e29-e73d-23a6-5c6f-0267b1e669b6@samba.org>
On Thu, Mar 12, 2020 at 2:08 AM Stefan Metzmacher <metze@samba.org> wrote:
>
> The whole discussion was triggered by the introduction of a completely
> new fsinfo() call:
>
> Would you propose to have 'at_flags' and 'resolve_flags' passed in here?
Yes, I think that would be the way to go.
> > If we need linkat2() and friends, so be it. Do we?
>
> Yes, I'm going to propose something like this, as it would make the life
> much easier for Samba to have the new features available on all path
> based syscalls.
Will samba actually use them? I think we've had extensions before that
weren't worth the non-portability pain?
But yes, if we have a major package like samba use it, then by all
means let's add linkat2(). How many things are we talking about? We
have a number of system calls that do *not* take flags, but do do
pathname walking. I'm thinking things like "mkdirat()"?)
> In addition I'll propose to have a way to specify the source of
> removeat and unlinkat also by fd in addition to the the source parent fd
> and relative path, the reason are also to detect races of path
> recycling.
Would that be basically just an AT_EMPTY_PATH kind of thing? IOW,
you'd be able to remove a file by doing
fd = open(path.., O_PATH);
unlinkat(fd, "", AT_EMPTY_PATH);
Hmm. We have _not_ allowed filesystem changes without that last
component lookup. Of course, with our dentry model, we *can* do it,
but this smells fairly fundamental to me.
It might avoid some of the extra system calls (ie you could use
openat2() to do the path walking part, and then
unlinkat(AT_EMPTY_PATH) to remove it, and have a "fstat()" etc in
between the verify that it's the right type of file or whatever - and
you'd not need an unlinkat2() with resolve flags).
I think Al needs to ok this kind of change. Maybe you've already
discussed it with him and I just missed it.
Linus
next prev parent reply other threads:[~2020-03-12 16:25 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-09 14:00 [PATCH 00/14] VFS: Filesystem information [ver #18] David Howells
2020-03-09 14:00 ` [PATCH 01/14] VFS: Add additional RESOLVE_* flags " David Howells
2020-03-09 20:56 ` Stefan Metzmacher
2020-03-09 21:13 ` David Howells
[not found] ` <20200310005549.adrn3yf4mbljc5f6@yavin>
2020-03-10 1:14 ` Linus Torvalds
2020-03-10 7:25 ` David Howells
2020-03-11 17:59 ` Linus Torvalds
2020-03-12 9:08 ` Stefan Metzmacher
2020-03-12 16:24 ` Linus Torvalds [this message]
2020-03-12 17:11 ` Stefan Metzmacher
2020-03-12 19:37 ` Al Viro
2020-03-12 21:48 ` Jeremy Allison
[not found] ` <20200313095901.tdv4vl7envypgqfz@yavin>
2020-03-13 16:48 ` Jeremy Allison
2020-03-13 18:28 ` Al Viro
2020-03-13 18:35 ` Jeremy Allison
2020-03-16 14:20 ` Aleksa Sarai
2020-03-12 19:25 ` Al Viro
2020-03-12 16:56 ` David Howells
2020-03-12 18:09 ` Linus Torvalds
2020-03-09 14:01 ` [PATCH 02/14] fsinfo: Add fsinfo() syscall to query filesystem information " David Howells
2020-03-10 9:31 ` Christian Brauner
2020-03-10 9:32 ` [PATCH v19 01/14] fsinfo: Add fsinfo() syscall to query filesystem information Christian Brauner
2020-03-10 9:32 ` [PATCH v19 14/14] arch: wire up fsinfo syscall Christian Brauner
2020-03-09 14:01 ` [PATCH 03/14] fsinfo: Provide a bitmap of supported features [ver #18] David Howells
2020-03-09 14:01 ` [PATCH 04/14] fsinfo: Allow retrieval of superblock devname, options and stats " David Howells
2020-03-09 14:01 ` [PATCH 05/14] fsinfo: Allow fsinfo() to look up a mount object by ID " David Howells
2020-03-09 14:01 ` [PATCH 06/14] fsinfo: Add a uniquifier ID to struct mount " David Howells
2020-03-09 14:01 ` [PATCH 07/14] fsinfo: Allow mount information to be queried " David Howells
2020-03-10 9:04 ` Miklos Szeredi
2020-03-09 14:02 ` [PATCH 08/14] fsinfo: Allow the mount topology propogation flags to be retrieved " David Howells
2020-03-10 8:42 ` Christian Brauner
2020-03-09 14:02 ` [PATCH 09/14] fsinfo: Provide notification overrun handling support " David Howells
2020-03-09 14:02 ` [PATCH 10/14] fsinfo: sample: Mount listing program " David Howells
2020-03-09 14:02 ` [PATCH 11/14] fsinfo: Add API documentation " David Howells
2020-03-09 14:02 ` [PATCH 12/14] fsinfo: Add support for AFS " David Howells
2020-03-09 14:02 ` [PATCH 13/14] fsinfo: Example support for Ext4 " David Howells
2020-03-09 14:02 ` [PATCH 14/14] fsinfo: Example support for NFS " David Howells
2020-03-09 17:50 ` [PATCH 00/14] VFS: Filesystem information " Jeff Layton
2020-03-09 19:22 ` Andres Freund
2020-03-09 22:49 ` Jeff Layton
2020-03-10 0:18 ` Andres Freund
2020-03-09 20:02 ` Miklos Szeredi
2020-03-09 22:52 ` David Howells
2020-03-10 9:18 ` Miklos Szeredi
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