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Message-ID: <20081204041450.GH28946@ZenIV.linux.org.uk>
Date: Thu, 4 Dec 2008 04:14:50 +0000
From: Al Viro <viro@...IV.linux.org.uk>
To: axboe@...nel.dk
Cc: linux-kernel@...r.kernel.org
Subject: [RFC] cdrom weirdness
1) CDROM_LOCKDOOR sets a global variable (keeplocked) that affects all
cdroms. Intentional?
2) cdrom_dvd_rw_close_write() call can be delayed indefinitely by keeping
an ioctl-only (opened with O_NDELAY) descriptor.
3) open cdrom for data, have the door locked, keep fd opened.
open it again for write, have the open fail and cleanup in cdrom_open()
will happily unlock the door for you. I'd change that to "lock if we
had no lockers, unlock on failure exit if we did lock", but there's
an interesting comment:
/* Something failed. Try to unlock the drive, because some drivers
(notably ide-cd) lock the drive after every command.
...
What the hell is that about? It's not "some drivers", AFAICT - it's
been done explicitly in open_for_data(). Or is there something
really driver-specific in it?
4) while we are at it, if you clear lockdoor via sysctl while something has
cdrom opened - no unlock on close for you.
5) autoeject happens on the last close *IF* the last file happens to be
opened for data. IOW, if some crap has opened it ioctl-only and kept
that opened after everyone else has closed - no autoeject for you.
6) /*
* flush cache on last write release
*/
if (CDROM_CAN(CDC_RAM) && !cdi->use_count && cdi->for_data)
cdrom_close_write(cdi);
is interesting, seeing that nothing has ever touched ->for_data, for
values of "ever" including "since the code in question had been merged
into the tree"...
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