From: Karel Zak <kzak@redhat.com>
To: Michal Suchanek <msuchanek@suse.de>
Cc: util-linux@vger.kernel.org
Subject: Re: [PATCH] blkid: open device in nonblock mode.
Date: Tue, 5 Nov 2019 12:41:22 +0100 [thread overview]
Message-ID: <20191105114122.o3cjzfnoy3hp2rbm@10.255.255.10> (raw)
In-Reply-To: <20191104202315.4879-1-msuchanek@suse.de>
On Mon, Nov 04, 2019 at 09:23:15PM +0100, Michal Suchanek wrote:
> When autoclose is set (kernel default but many distributions reverse the
> setting) opening a CD-rom device causes the tray to close.
>
> The function of blkid is to report the current state of the device and
> not to change it. Hence it should use O_NONBLOCK when opening the
> device to avoid closing a CD-rom tray.
I can imagine this as optional solution (command line option), but I
have doubts to use O_NONBLOCK by default for all block devices. I have
no example, but it sounds like a way how to introduce regressions in
libblkid behavior. (Any kernel guy around?) Is it really only cdrom
driver(s) where O_NONBLOCK has any impact? What about USB, some random
SCSI, ... I don't know.
The another problem is that the library does not have to open the device,
you can use already open file descriptor (blkid_probe_set_device()).
So, in many cases the patch will have no effect.
> blkid is used liberally in scripts so it can potentially interfere with
> the user operating the CD-rom hardware.
It's better to use lsblk in script, it reads info from udev -- call
blindly blkid(8) is usually overkill.
Karel
--
Karel Zak <kzak@redhat.com>
http://karelzak.blogspot.com
next prev parent reply other threads:[~2019-11-05 11:41 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-04 20:23 [PATCH] blkid: open device in nonblock mode Michal Suchanek
2019-11-05 11:41 ` Karel Zak [this message]
2019-11-05 17:13 ` Michal Suchánek
2019-11-06 8:02 ` Michal Suchánek
2019-11-06 8:48 ` Karel Zak
2019-11-06 9:45 ` Michal Suchánek
2019-11-12 8:27 ` Anatoly Pugachev
2019-11-12 8:58 ` Karel Zak
2019-11-06 9:00 ` Karel Zak
2020-01-07 16:04 ` Karel Zak
2020-01-07 16:19 ` Michal Suchánek
2020-01-08 8:25 ` Karel Zak
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