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From: Aleksa Sarai <cyphar@cyphar.com>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Stefan Metzmacher" <metze@samba.org>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	"David Howells" <dhowells@redhat.com>,
	"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>,
	"Jeremy Allison" <jra@samba.org>, "Ralph Böhme" <slow@samba.org>,
	"Volker Lendecke" <vl@sernet.de>
Subject: Re: [PATCH 01/14] VFS: Add additional RESOLVE_* flags [ver #18]
Date: Tue, 17 Mar 2020 01:20:57 +1100	[thread overview]
Message-ID: <20200316142057.xo24zea3k5zwswra@yavin> (raw)
Message-ID: <20200316142057.0yuPdVFUm0IreGknW9ELQSqWlzBirbhkgpr45YFrMl8@z> (raw)
In-Reply-To: <20200313182844.GO23230@ZenIV.linux.org.uk>

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On 2020-03-13, Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Fri, Mar 13, 2020 at 08:59:01PM +1100, Aleksa Sarai wrote:
> > On 2020-03-12, Stefan Metzmacher <metze@samba.org> wrote:
> > > Am 12.03.20 um 17:24 schrieb Linus Torvalds:
> > > > 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()"?)
> > > 
> > > I haven't looked them up in detail yet.
> > > Jeremy can you provide a list?
> > > 
> > > Do you think we could route some of them like mkdirat() and mknodat()
> > > via openat2() instead of creating new syscalls?
> > 
> > I have heard some folks asking for a way to create a directory and get a
> > handle to it atomically -- so arguably this is something that could be
> > inside openat2()'s feature set (O_MKDIR?). But I'm not sure how popular
> > of an idea this is.
> 
> For fuck sake, *NO*!
> 
> We don't need any more multiplexors from hell.  mkdir() and open() have
> deeply different interpretation of pathnames (and anyone who asks for
> e.g. traversals of dangling symlinks on mkdir() is insane).  Don't try to
> mix those; even O_TMPFILE had been a mistake.

I agree that O_TMPFILE is a mess, and you're right that it wouldn't be a
good idea to fold it into open*(). But what is your opinion on a
hypothetical mkdirat2() which would let you get an fd to the directory
that was just created?

> We really don't need openat2() turning into another one.  Syscall table
> slots are not in a short supply, and the level of review one gets from
> "new syscall added" is higher than from "make fubar(2) recognize a new
> member in options->union_full_of_crap if it has RESOLVE_TO_WANK_WITH_RIGHT_HAND
> set in options->flags, affecting its behaviour in some odd ways".
> Which is a good thing, damnit.

You're quite right, and I don't intend openat2() to become another
ioctl-but-with-even-more-fun-semantics.

-- 
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>

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  parent reply	other threads:[~2020-03-19  8:10 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-09 14:00 [PATCH 00/14] VFS: Filesystem information " 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
2020-03-10  0:55   ` Aleksa Sarai
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
2020-03-12 17:11             ` Stefan Metzmacher
2020-03-12 19:37               ` Al Viro
2020-03-12 21:48               ` Jeremy Allison
2020-03-13  9:59               ` Aleksa Sarai
2020-03-13 10:00                 ` Aleksa Sarai
2020-03-13 16:48                 ` Jeremy Allison
2020-03-13 18:28                 ` Al Viro
2020-03-13 18:35                   ` Jeremy Allison
2020-03-16 14:21                   ` Aleksa Sarai [this message]
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
2020-03-13  9:53               ` Aleksa Sarai
2020-03-13  9:50         ` Aleksa Sarai
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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