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Groups > linux.kernel > #1635630
| From | Karel Zak <kzak@redhat.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 4/9] Implement fsopen() to prepare for a mount |
| Date | 2017-05-04 12:50 +0200 |
| Message-ID | <tDmuB-2fe-1@gated-at.bofh.it> (permalink) |
| References | <tD50J-7GP-3@gated-at.bofh.it> <tD50J-7GP-17@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Wed, May 03, 2017 at 05:05:08PM +0100, David Howells wrote:
> mfd = fsopen("ext4", -1, O_CLOEXEC);
> write(mfd, "d /dev/sdb1"); // note I'm ignoring write's length arg
Not sure about 'd', in many cases it is not device, for mount(2)
syscall we call it "source".
> write(mfd, "o noatime");
> write(mfd, "o acl");
> write(mfd, "o user_attr");
> write(mfd, "o iversion");
> write(mfd, "o ");
> write(mfd, "r /my/container"); // root inside the fs
> fsmount(mfd, container_fd, "/mnt", AT_NO_FOLLOW);
>
> mfd = fsopen("afs", -1);
> write(mfd, "d %grand.central.org:root.cell");
> write(mfd, "o cell=grand.central.org");
> write(mfd, "r /");
> fsmount(mfd, AT_FDCWD, "/mnt", 0);
>
> If an error is reported at any step, an error message may be available to be
> read() back (ENODATA will be reported if there isn't an error available) in
> the form:
>
> "e <subsys>:<problem>"
> "e SELinux:Mount on mountpoint not permitted"
>
> Once fsmount() has been called, further write() calls will incur EBUSY,
> even if the fsmount() fails. read() is still possible to retrieve error
> information.
The very basic mount(2) problem is that you have to parse
/proc/self/mountinfo to get information about the mounted filesystem.
It seems that your read() is also one way communication.
What we really need is to have a way how to specify *what* you want to
read. The error message is not enough, I want to know the finally used
mount options, mount ID, etc. It would be nice to have something like
fsmount(mfd, AT_FDCWD, "/mnt", 0);
write(mfd, "o");
read(mfd, ....); // read mount options
write(mdf, "i");
read(mfd, ....); // read mount ID
but it seems ugly. Maybe introduce another function like
fsinfo(mdf, "o", buf, bufsz)
to get mount options (etc.) and to avoid separate write & read.
> Netlink is not used because it is optional.
+1
Karel
--
Karel Zak <kzak@redhat.com>
http://karelzak.blogspot.com
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[RFC][PATCH 0/9] VFS: Introduce mount context David Howells <dhowells@redhat.com> - 2017-05-03 18:10 +0200
[PATCH 1/9] Provide a function to create a NUL-terminated string from unterminated data David Howells <dhowells@redhat.com> - 2017-05-03 18:10 +0200
Re: [PATCH 1/9] Provide a function to create a NUL-terminated string from unterminated data Jeff Layton <jlayton@poochiereds.net> - 2017-05-03 19:00 +0200
Re: [PATCH 1/9] Provide a function to create a NUL-terminated string from unterminated data Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2017-05-03 21:30 +0200
Re: [PATCH 1/9] Provide a function to create a NUL-terminated string from unterminated data David Howells <dhowells@redhat.com> - 2017-05-03 22:20 +0200
[PATCH 4/9] Implement fsopen() to prepare for a mount David Howells <dhowells@redhat.com> - 2017-05-03 18:10 +0200
Re: [PATCH 4/9] Implement fsopen() to prepare for a mount Jeff Layton <jlayton@poochiereds.net> - 2017-05-03 20:40 +0200
Re: [PATCH 4/9] Implement fsopen() to prepare for a mount David Howells <dhowells@redhat.com> - 2017-05-03 20:50 +0200
Re: [PATCH 4/9] Implement fsopen() to prepare for a mount Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2017-05-03 22:50 +0200
Re: [PATCH 4/9] Implement fsopen() to prepare for a mount David Howells <dhowells@redhat.com> - 2017-05-04 15:00 +0200
Re: [PATCH 4/9] Implement fsopen() to prepare for a mount David Howells <dhowells@redhat.com> - 2017-05-04 15:00 +0200
Re: [PATCH 4/9] Implement fsopen() to prepare for a mount Karel Zak <kzak@redhat.com> - 2017-05-04 12:50 +0200
Re: [PATCH 4/9] Implement fsopen() to prepare for a mount David Howells <dhowells@redhat.com> - 2017-05-04 15:10 +0200
Re: [PATCH 4/9] Implement fsopen() to prepare for a mount Karel Zak <kzak@redhat.com> - 2017-05-04 15:40 +0200
Re: [PATCH 4/9] Implement fsopen() to prepare for a mount Jeff Layton <jlayton@redhat.com> - 2017-05-09 20:50 +0200
Re: [PATCH 4/9] Implement fsopen() to prepare for a mount Miklos Szeredi <mszeredi@redhat.com> - 2017-05-08 17:20 +0200
Re: [PATCH 4/9] Implement fsopen() to prepare for a mount David Howells <dhowells@redhat.com> - 2017-05-09 01:20 +0200
[PATCH 5/9] Implement fsmount() to effect a pre-configured mount David Howells <dhowells@redhat.com> - 2017-05-03 18:10 +0200
[PATCH 2/9] Clean up whitespace in fs/namespace.c David Howells <dhowells@redhat.com> - 2017-05-03 18:10 +0200
[PATCH 8/9] proc: Support the mount context in procfs David Howells <dhowells@redhat.com> - 2017-05-03 18:10 +0200
[PATCH 7/9] procfs: Move proc_fill_super() to fs/proc/root.c David Howells <dhowells@redhat.com> - 2017-05-03 18:10 +0200
Re: [RFC][PATCH 0/9] VFS: Introduce mount context Jeff Layton <jlayton@poochiereds.net> - 2017-05-03 18:50 +0200
Re: [RFC][PATCH 0/9] VFS: Introduce mount context David Howells <dhowells@redhat.com> - 2017-05-03 19:00 +0200
Re: [RFC][PATCH 0/9] VFS: Introduce mount context Jeff Layton <jlayton@poochiereds.net> - 2017-05-03 19:30 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Joe Perches <joe@perches.com> - 2017-05-03 20:30 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-03 20:40 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Joe Perches <joe@perches.com> - 2017-05-03 20:50 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-03 22:20 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Matthew Wilcox <willy@infradead.org> - 2017-05-03 22:40 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-03 23:20 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Joe Perches <joe@perches.com> - 2017-05-03 23:40 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Julia Lawall <julia.lawall@lip6.fr> - 2017-05-04 08:30 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-04 11:30 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Joe Perches <joe@perches.com> - 2017-05-04 16:40 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2017-05-03 23:50 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-04 12:30 +0200
Re: [RFC][PATCH 0/9] VFS: Introduce mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-05 16:40 +0200
Re: [RFC][PATCH 0/9] VFS: Introduce mount context David Howells <dhowells@redhat.com> - 2017-05-05 17:50 +0200
Re: [RFC][PATCH 0/9] VFS: Introduce mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-08 10:30 +0200
Re: [RFC][PATCH 0/9] VFS: Introduce mount context David Howells <dhowells@redhat.com> - 2017-05-08 10:40 +0200
Re: [RFC][PATCH 0/9] VFS: Introduce mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-08 10:50 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-08 17:10 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-09 01:00 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-09 10:10 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-09 11:40 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-09 13:10 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-09 11:50 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-09 14:10 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Jeff Layton <jlayton@redhat.com> - 2017-05-09 21:00 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-10 09:30 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-10 10:10 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Jeff Layton <jlayton@redhat.com> - 2017-05-10 15:30 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-10 15:40 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Jeff Layton <jlayton@redhat.com> - 2017-05-10 15:40 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-10 15:40 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-10 15:40 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Jeff Layton <jlayton@redhat.com> - 2017-05-10 15:50 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-09 12:00 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-09 14:40 +0200
Re: [PATCH 3/9] VFS: Introduce a mount context Karel Zak <kzak@redhat.com> - 2017-05-10 14:50 +0200
Re: [RFC][PATCH 0/9] VFS: Introduce mount context Djalal Harouni <tixxdz@gmail.com> - 2017-05-08 19:10 +0200
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