From: bfields@fieldses.org (J. Bruce Fields)
To: Drew DeVault <sir@cmpwn.com>
Cc: Matthew Wilcox <willy@infradead.org>,
linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org,
Aleksa Sarai <cyphar@cyphar.com>
Subject: Re: [RFC PATCH] fs: introduce mkdirat2 syscall for atomic mkdir
Date: Mon, 1 Mar 2021 14:09:03 -0500 [thread overview]
Message-ID: <20210301190903.GD14881@fieldses.org> (raw)
In-Reply-To: <C9L7SV0Z2GZR.K2C3O186WDJ7@taiga>
On Sun, Feb 28, 2021 at 08:57:20AM -0500, Drew DeVault wrote:
> On Sat Feb 27, 2021 at 11:03 PM EST, Matthew Wilcox wrote:
> > > 1. Program A creates a directory
> > > 2. Program A is pre-empted
> > > 3. Program B deletes the directory
> > > 4. Program A creates a file in that directory
> > > 5. RIP
> >
> > umm ... program B deletes the directory. program A opens it in order to
> > use openat(). program A gets ENOENT and exits, confused. that's the
> > race you're removing here -- and it seems fairly insignificant to me.
>
> Yes, that is the race being eliminated here. Instead of this, program A
> has an fd which holds a reference to the directory, so it just works. A
> race is a race. It's an oversight in the API.
Step 4 still fails either way, because you can't create a file in an
unlinked directory, even if you hold a reference to that directory.
What's the behavior change at step 4 that you're hoping for?
--b.
next prev parent reply other threads:[~2021-03-01 19:15 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-28 0:25 [RFC PATCH] fs: introduce mkdirat2 syscall for atomic mkdir Drew DeVault
2021-02-28 2:13 ` Al Viro
2021-02-28 2:21 ` Drew DeVault
2021-02-28 2:58 ` Al Viro
2021-02-28 13:56 ` Drew DeVault
2021-03-01 19:02 ` J. Bruce Fields
2021-03-08 13:50 ` Stefan Metzmacher
2021-02-28 2:24 ` Matthew Wilcox
2021-02-28 2:26 ` Drew DeVault
2021-02-28 4:03 ` Matthew Wilcox
2021-02-28 13:57 ` Drew DeVault
2021-03-01 19:09 ` J. Bruce Fields [this message]
2021-03-01 19:35 ` Matthew Wilcox
2021-03-01 20:10 ` J. Bruce Fields
2021-03-02 8:24 ` Miklos Szeredi
2021-03-02 7:13 ` Amir Goldstein
2021-03-03 2:39 ` Aleksa Sarai
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