From: "Alejandro Colomar (man-pages)" <alx.manpages@gmail.com>
To: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Stephen Kitt <steve@sk2.org>,
linux-man@vger.kernel.org,
Michael Kerrisk <mtk.manpages@gmail.com>,
linux-kernel@vger.kernel.org
Subject: Re: [patch] close_range.2: new page documenting close_range(2)
Date: Thu, 10 Dec 2020 15:36:42 +0100 [thread overview]
Message-ID: <0ea38a7a-1c64-086e-3d64-38686f5b7856@gmail.com> (raw)
In-Reply-To: <20201209105618.okw5lgcdikg5bvae@wittgenstein>
Hi Christian,
Thanks for confirming that behavior. Seems reasonable.
I was wondering...
If this call is equivalent to unshare(2)+{close(2) in a loop},
shouldn't it fail for the same reasons those syscalls can fail?
What about the following errors?:
From unshare(2):
EPERM The calling process did not have the required privi‐
leges for this operation.
From close(2):
EBADF fd isn't a valid open file descriptor.
OK, this one can't happen with the current code.
Let's say there are fds 1 to 10, and you call 'close_range(20,30,0)'.
It's a no-op (although it will still unshare if the flag is set).
But souldn't it fail with EBADF?
EINTR The close() call was interrupted by a signal; see sig‐
nal(7).
EIO An I/O error occurred.
ENOSPC, EDQUOT
On NFS, these errors are not normally reported against
the first write which exceeds the available storage
space, but instead against a subsequent write(2),
fsync(2), or close().
Thanks,
Alex
On 12/9/20 11:56 AM, Christian Brauner wrote:
> On Wed, Dec 09, 2020 at 11:44:22AM +0100, Alejandro Colomar (man-pages) wrote:
>> Hey Christian,
>>
>> I have a question for you below.
>>
>> Thanks,
>
> Hey Alex,
>
> Sure!
[...]
>>
>> AFAICS after reading the code, if the unsharing fails,
>> it will not close any file descriptors (please correct me if I'm wrong).
>>
>> Just wanted to be sure that it was the intended behavior with you,
>> and if so, it would be good to document it in the page.
>
> Yes, this is intended because if the unshare fails we haven't yet
> actually started closing anything so we're before the point of no
> return where we ignore failures. So we can let userspace decide whether
> they want to retry without CLOSE_RANGE_UNSHARE.
>
> Christian
>
--
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es
next prev parent reply other threads:[~2020-12-10 16:49 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-08 21:51 [patch] close_range.2: new page documenting close_range(2) Stephen Kitt
2020-12-09 8:50 ` Michael Kerrisk (man-pages)
2020-12-09 9:40 ` Christian Brauner
2020-12-09 9:43 ` Stephen Kitt
2020-12-09 9:47 ` Alejandro Colomar (man-pages)
2020-12-10 22:40 ` Michael Kerrisk (man-pages)
2020-12-09 9:58 ` Christian Brauner
2020-12-09 10:44 ` Alejandro Colomar (man-pages)
2020-12-09 10:56 ` Christian Brauner
2020-12-10 14:36 ` Alejandro Colomar (man-pages) [this message]
2020-12-12 12:14 ` Christian Brauner
2020-12-12 17:58 ` Alejandro Colomar (man-pages)
2020-12-18 10:12 ` Ping: " Alejandro Colomar (man-pages)
2020-12-18 10:14 ` Stephen Kitt
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