From: Andy Lutomirski <luto@amacapital.net>
To: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
Linux API <linux-api@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Linux FS Devel <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 29/38] vfs: syscall: Add fsconfig() for configuring and managing a context [ver #10]
Date: Fri, 27 Jul 2018 14:57:51 -0700 [thread overview]
Message-ID: <CALCETrWDGa+ut=xsoki+XFKzdD7KruJJicfH1tKdBtywLuk7iQ@mail.gmail.com> (raw)
In-Reply-To: <7034.1532728300@warthog.procyon.org.uk>
On Fri, Jul 27, 2018 at 2:51 PM, David Howells <dhowells@redhat.com> wrote:
> Andy Lutomirski <luto@amacapital.net> wrote:
>
>> Unless I'm rather confused, you have two or possibly three ways to
>> pass in an open fd. Can you clarify what the difference is and/or
>> remove all but one of them?
>
> No, they're not equivalent.
>
>> > (*) fsconfig_set_path: A non-empty path is specified. The parameter must
>> > be expecting a path object. value points to a NUL-terminated string
>> > that is the path and aux is a file descriptor at which to start a
>> > relative lookup or AT_FDCWD.
>
> So, an example:
>
> fsconfig(fd, fsconfig_set_path, "source", "/dev/sda1", AT_FDCWD);
>
> I don't want to require that the caller open /dev/sda1 and pass in an fd as
> that might prevent the filesystem from "holding" it exclusively.
>
>> > (*) fsconfig_set_path_empty: As fsconfig_set_path, but with AT_EMPTY_PATH
>> > implied.
>
> You can't do:
>
> fsconfig(fd, fsconfig_set_path, "source", "", dir_fd);
>
> because AT_EMPTY_PATH cannot be specified directly[*]. What you do instead is:
>
> fsconfig(fd, fsconfig_set_path_empty, "source", "", dir_fd);
>
> [*] Not without a 6-arg syscall or some other way of passing it.
Are there still architectures that have problems with 6-arg syscalls?
>
> I *could* require that the caller must call open(O_PATH) or openat(O_PATH)
> before calling fsconfig() - so you don't pass a string, but only a path-fd.
>
>> > (*) fsconfig_set_fd: An open file descriptor is specified. value must
>> > be NULL and aux indicates the file descriptor.
>
> See fd=%u on fuse. I think it's cleaner to do:
>
> fsconfig(fd, fsconfig_set_fd, "source", NULL, control_fd);
>
> saying explicitly that there's an open file to be passed rather than:
>
> fsconfig(fd, fsconfig_set_path, "source", NULL, control_fd);
Hmm. That should probably be clearly documented. I suppose that, as
long as there is never a case where fsconfig_set_path and
fsconfig_set_fd both succeed, then it's not a big deal.
next prev parent reply other threads:[~2018-07-27 23:22 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-27 17:31 [PATCH 00/38] VFS: Introduce filesystem context [ver #10] David Howells
2018-07-27 17:31 ` [PATCH 01/38] vfs: syscall: Add open_tree(2) to reference or clone a mount " David Howells
2018-07-27 17:31 ` [PATCH 02/38] vfs: syscall: Add move_mount(2) to move mounts around " David Howells
2018-07-27 17:31 ` [PATCH 03/38] teach move_mount(2) to work with OPEN_TREE_CLONE " David Howells
2018-07-27 17:31 ` [PATCH 04/38] vfs: Suppress MS_* flag defs within the kernel unless explicitly enabled " David Howells
2018-07-27 17:31 ` [PATCH 05/38] vfs: Introduce the basic header for the new mount API's filesystem context " David Howells
2018-07-27 17:32 ` [PATCH 06/38] vfs: Introduce logging functions " David Howells
2018-07-27 17:32 ` [PATCH 07/38] vfs: Add configuration parser helpers " David Howells
2018-07-27 17:32 ` [PATCH 08/38] vfs: Add LSM hooks for the new mount API " David Howells
2018-07-27 17:32 ` [PATCH 09/38] selinux: Implement the new mount API LSM hooks " David Howells
2018-07-27 17:32 ` [PATCH 10/38] smack: Implement filesystem context security " David Howells
2018-07-27 17:32 ` [PATCH 11/38] apparmor: Implement security hooks for the new mount API " David Howells
2018-07-27 17:32 ` [PATCH 12/38] vfs: Pass key and value into LSM and FS and provide a helper parser " David Howells
2018-07-27 17:32 ` [PATCH 13/38] tomoyo: Implement security hooks for the new mount API " David Howells
2018-07-28 2:29 ` Tetsuo Handa
2018-07-30 10:49 ` David Howells
2018-07-27 17:32 ` [PATCH 14/38] vfs: Separate changing mount flags full remount " David Howells
2018-07-27 17:33 ` [PATCH 15/38] vfs: Implement a filesystem superblock creation/configuration context " David Howells
2018-07-27 17:33 ` [PATCH 16/38] vfs: Remove unused code after filesystem context changes " David Howells
2018-07-27 17:33 ` [PATCH 17/38] procfs: Move proc_fill_super() to fs/proc/root.c " David Howells
2018-07-27 17:33 ` [PATCH 18/38] proc: Add fs_context support to procfs " David Howells
2018-07-27 17:33 ` [PATCH 19/38] ipc: Convert mqueue fs to fs_context " David Howells
2018-07-27 17:33 ` [PATCH 20/38] cpuset: Use " David Howells
2018-07-27 17:33 ` [PATCH 21/38] kernfs, sysfs, cgroup, intel_rdt: Support " David Howells
2018-07-27 17:33 ` [PATCH 22/38] hugetlbfs: Convert to " David Howells
2018-07-27 17:33 ` [PATCH 23/38] vfs: Remove kern_mount_data() " David Howells
2018-07-27 17:34 ` [PATCH 24/38] vfs: Provide documentation for new mount API " David Howells
2018-07-27 17:34 ` [PATCH 25/38] Make anon_inodes unconditional " David Howells
2018-07-27 20:04 ` Randy Dunlap
2018-07-30 10:52 ` David Howells
2018-07-27 17:34 ` [PATCH 26/38] vfs: syscall: Add fsopen() to prepare for superblock creation " David Howells
2018-07-27 17:34 ` [PATCH 27/38] vfs: Implement logging through fs_context " David Howells
2018-07-27 17:34 ` [PATCH 28/38] vfs: Add some logging to the core users of the fs_context log " David Howells
2018-07-27 17:34 ` [PATCH 29/38] vfs: syscall: Add fsconfig() for configuring and managing a context " David Howells
2018-07-27 19:42 ` Andy Lutomirski
2018-07-27 21:51 ` David Howells
2018-07-27 21:57 ` Andy Lutomirski [this message]
2018-07-27 22:27 ` David Howells
2018-07-27 22:32 ` Jann Horn
2018-07-29 8:50 ` David Howells
2018-07-29 11:14 ` Jann Horn
2018-07-30 12:32 ` David Howells
2018-07-27 17:34 ` [PATCH 30/38] vfs: syscall: Add fsmount() to create a mount for a superblock " David Howells
2018-07-27 19:27 ` Andy Lutomirski
2018-07-27 19:43 ` Andy Lutomirski
2018-07-27 22:09 ` David Howells
2018-07-27 22:06 ` David Howells
2018-07-27 17:34 ` [PATCH 31/38] vfs: syscall: Add fspick() to select a superblock for reconfiguration " David Howells
2018-07-27 17:34 ` [PATCH 32/38] afs: Add fs_context support " David Howells
2018-07-27 17:35 ` [PATCH 33/38] afs: Use fs_context to pass parameters over automount " David Howells
2018-07-27 17:35 ` [PATCH 34/38] vfs: syscall: Add fsinfo() to query filesystem information " David Howells
2018-07-27 19:35 ` Andy Lutomirski
2018-07-27 22:12 ` David Howells
2018-07-27 23:14 ` Jann Horn
2018-07-27 23:49 ` David Howells
2018-07-28 0:14 ` Anton Altaparmakov
2018-07-27 23:51 ` David Howells
2018-07-27 23:58 ` Jann Horn
2018-07-28 0:08 ` David Howells
2018-07-30 14:48 ` David Howells
2018-07-31 4:16 ` Al Viro
2018-07-31 12:39 ` David Howells
2018-07-31 13:20 ` David Howells
2018-07-31 23:49 ` Darrick J. Wong
2018-08-01 1:07 ` David Howells
2018-07-27 17:35 ` [PATCH 35/38] afs: Add fsinfo support " David Howells
2018-07-27 17:35 ` [PATCH 36/38] vfs: Add a sample program for the new mount API " David Howells
2018-07-29 11:37 ` Pavel Machek
2018-07-30 12:23 ` David Howells
2018-07-30 14:31 ` Pavel Machek
2018-07-30 18:08 ` Matthew Wilcox
2018-07-30 18:16 ` Pavel Machek
2018-07-30 18:18 ` Linus Torvalds
2018-07-30 18:38 ` Matthew Wilcox
2018-07-30 18:59 ` Linus Torvalds
2018-07-30 19:49 ` Matthew Wilcox
2018-07-30 21:02 ` Theodore Y. Ts'o
2018-07-30 21:23 ` Pavel Machek
2018-07-30 23:58 ` Matthew Wilcox
2018-07-31 0:58 ` Theodore Y. Ts'o
2018-07-31 9:40 ` Pavel Machek
2018-07-31 10:11 ` David Howells
2018-07-31 11:34 ` Pavel Machek
2018-07-31 12:07 ` Matthew Wilcox
2018-07-31 12:28 ` Pavel Machek
2018-07-31 13:33 ` Al Viro
2018-07-31 13:00 ` David Howells
2018-07-31 19:39 ` Pavel Machek
2018-07-31 21:00 ` David Howells
2018-07-31 21:21 ` Linus Torvalds
2018-07-31 21:38 ` David Howells
2018-07-30 20:47 ` Pavel Machek
2018-07-30 15:33 ` David Howells
2018-07-30 17:30 ` Pavel Machek
2018-07-30 17:54 ` Linus Torvalds
2018-07-30 18:16 ` Pavel Machek
2018-07-27 17:35 ` [PATCH 37/38] vfs: Allow fsinfo() to query what's in an fs_context " David Howells
2018-07-27 17:35 ` [PATCH 38/38] vfs: Allow fsinfo() to be used to query an fs parameter description " David Howells
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CALCETrWDGa+ut=xsoki+XFKzdD7KruJJicfH1tKdBtywLuk7iQ@mail.gmail.com' \
--to=luto@amacapital.net \
--cc=dhowells@redhat.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=torvalds@linux-foundation.org \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).