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SubjectRe: Can't eject a previously mounted CD?
Ed Sweetman wrote:
> I'd have to say the december 17th listed changes are the culprit here.
> I'm definitely not up to figuring out what change is the bad one. If
> any of the cdrom/ide-cd people wanna have me get some data from them
> then just tell me how. I've tried viewing the debug output from the
> modules with no success in figuring out the problem.

Luckily for me, I built my cdrom drivers as modules, so I could play :)
I turned on debugging, and noticed that cdi->use_count continues to increment by
2 for each access. In cdrom_release, only one cdi->use_count-- exists, so the
driver never gets to 0 use count and releases. I noticed in
drivers/cdrom/cdrom.c line 753:

if (!ret) cdi->use_count++;

Which is our second increment, but I can't find two decrements, because the
check further down won't ever be true if the above is true. Hence, two
increments and only 1 dec when we reach cdrom_release. What I did, was add a
conditional decrement right before the open_for_data call, which makes the value
of use_count like it used to be prior to the Mt. Rainier patches. Seems kinda
hacky :)


--- /usr/src/linux/drivers/cdrom/cdrom.c 2003-12-25 09:53:59.000000000 -0800
+++ linux-2.6.0-mm1/drivers/cdrom/cdrom.c 2003-12-28 19:42:04.174098225 -0800
@@ -744,4 +744,7 @@

+ if (cdi->use_count > 0)
+ cdi->use_count--;
/* if this was a O_NONBLOCK open and we should honor the flags,
* do a quick open without drive/disc integrity checks. */
@@ -931,5 +934,5 @@
struct cdrom_device_ops *cdo = cdi->ops;

- cdinfo(CD_CLOSE, "entering cdrom_release\n");
+ cdinfo(CD_CLOSE, "entering cdrom_release\n");

if (cdi->use_count > 0)

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