[66/71] cdrom: always check_disk_change() on open

From: Greg KH
Date: Thu May 19 2011 - 14:10:56 EST

2.6.38-stable review patch. If anyone has any objections, please let us know.


From: Tejun Heo <tj@xxxxxxxxxx>

commit bf2253a6f00e8fea5b026e471e9f0d0a1b3621f2 upstream.

cdrom_open() called check_disk_change() after the rest of open path
succeeded which leads to the following bizarre behavior.

* After media change, if the device opened without O_NONBLOCK,
open_for_data() naturally fails with -ENOMEDIA and
check_disk_change() is never called. The media is known to be gone
and the open failure makes it obvious to the userland but device
invalidation never happens.

* But if the device is opened with O_NONBLOCK, all the checks are
bypassed and cdrom_open() doesn't notice that the media is not there
and check_disk_change() is called and invalidation happens.

There's nothing to be gained by avoiding calling check_disk_change()
on open failure. Common cases end up calling check_disk_change()
anyway. All we get is inconsistent behavior.

Fix it by moving check_disk_change() invocation to the top of
cdrom_open() so that it always gets called regardless of how the rest
of open proceeds.

Stable: 2.6.38

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Reported-by: Amit Shah <amit.shah@xxxxxxxxxx>
Tested-by: Amit Shah <amit.shah@xxxxxxxxxx>
Signed-off-by: Jens Axboe <jaxboe@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

drivers/cdrom/cdrom.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -986,6 +986,9 @@ int cdrom_open(struct cdrom_device_info

cdinfo(CD_OPEN, "entering cdrom_open\n");

+ /* open is event synchronization point, check events first */
+ check_disk_change(bdev);
/* if this was a O_NONBLOCK open and we should honor the flags,
* do a quick open without drive/disc integrity checks. */
@@ -1012,9 +1015,6 @@ int cdrom_open(struct cdrom_device_info

cdinfo(CD_OPEN, "Use count for \"/dev/%s\" now %d\n",
cdi->name, cdi->use_count);
- /* Do this on open. Don't wait for mount, because they might
- not be mounting, but opening with O_NONBLOCK */
- check_disk_change(bdev);
return 0;
if (CDROM_CAN(CDC_LOCK) && cdi->options & CDO_LOCK) {

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/