On Fri, Feb 23, 2018 at 11:14:41AM +0100, Carlos Maiolino wrote:
> On Thu, Feb 22, 2018 at 01:00:16PM -0600, Steve Kenton wrote:
> > The readable size of new, factory blank, optical media can change via user
> > space ioctl(SG_IO) commands to format overwritable media such as DVD+RW for
> > a UDF filesystem or write to sequential media such as DVD-R for an ISO-9660
> > filesystem. However there appears to be no easy way to update the size used
> > by the block layer from the initial value of zero other than ejecting and
> > reinserting the media. This is a long standing issue which programs such as
> > growisofs work around by automatically opening and closing the tray at the
> > end of a session so the newly created filesystem becomes
> > mountable/readable. This can be problematic when using a slot load drive.
> >
This should go to linux- block btw, not linux-fsdevel, cc'ing them
> > Making the BLKRRPART ioctl call fops->revalidate_disk() =>
> > sr_revalidate_disk() in sr.c resolves the issue for optical media and
> > should be a rare and benign operation if ever called for non-optical media
> > => sd_revalidate_disk() in sd.c.
> >
>
> Please use checkpatch.pl and break the comment description to at most
> 80chars/line
>
> > Signed-off-by: Steve Kenton <sken...@ou.edu>
> > Signed-off-by: Thomas Schmitt <scdbac...@gmx.net>
> > ---
> > I discussed this with Thomas Schmitt the maintainer of the xorriso burner
> > program to define the problem and suggest a fix.
> >
> > Loading a factory blank DVD+RW needing to be "de-iced" gives the results
> > below before and after format full using xorriso but *NOT* ejecting the
> > media
> >
> > hdi@hdi-H110N:/sys/block/sr0$ dd if=/dev/sr0 of=/dev/null bs=2k
> > dd: error reading ‘/dev/sr0’: Input/output error
> > 0+0 records in
> > 0+0 records out
> > 0 bytes (0 B) copied, 0.0275589 s, 0.0 kB/s
> >
> > hdi@hdi-H110N:/sys/block/sr0$ cat size
> > 4
> >
> > hdi@hdi-H110N:/sys/block/sr0$ xorriso -dev /dev/sr0 -format full
> >
> > hdi@hdi-H110N:/sys/block/sr0$ dd if=/dev/sr0 of=/dev/null bs=2k
> > 0+0 records in
> > 0+0 records out
> > 0 bytes (0 B) copied, 0.000280081 s, 0.0 kB/s
> >
> > hdi@hdi-H110N:/sys/block/sr0$ cat size
> > 0
> >
> > Here are the results after deleting and then rescanning the optial drive
> > via sysfs
> > echo offline > state echo 1 > delete echo - - - > scan
> > *WITHOUT* ejecting the media
> >
> > hdi@hdi-H110N:/sys/block/sr0/device$ dd if=/dev/sr0 of=/dev/null bs=2k
> > count=1
> > 1+0 records in
> > 1+0 records out
> > 2048 bytes (2.0 kB) copied, 0.0624783 s, 32.8 kB/s
> >
> > hdi@hdi-H110N:/sys/block/sr0$ cat size
> > 9180416
> >
> > With this patch applied running a small program to perform ioctl(BLKRRPART)
> > on /dev/sr0 produces similar results with a blank DVD-R after writing to
> > the disc using xorriso. Again, *WITHOUT* ejecting and reinserting the
> > media. Much nicer than the spin down and delete then scan for the device
> > again business, I think :-)
> >
> > hdi@hdi-H110N:/sys/block/sr0$ cat size
> > 4
> >
> > ./blkrrpart /dev/sr0
> >
> > hdi@hdi-H110N:/sys/block/sr0$ cat size
> > 16256
> >
> >
> > block/ioctl.c | 8 ++++++--
> > 1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/block/ioctl.c b/block/ioctl.c
> > index 1668506d8ed8..da79e9ba44ba 100644
> > --- a/block/ioctl.c
> > +++ b/block/ioctl.c
> > @@ -163,14 +163,18 @@ int __blkdev_reread_part(struct block_device *bdev)
> > {
> > struct gendisk *disk = bdev->bd_disk;
> >
> > - if (!disk_part_scan_enabled(disk) || bdev != bdev->bd_contains)
> > + if (bdev != bdev->bd_contains) // must be whole disk
>
> ^^ /* Comment */
> > return -EINVAL;
> > +
> > if (!capable(CAP_SYS_ADMIN))
> > return -EACCES;
> >
> > lockdep_assert_held(&bdev->bd_mutex);
> >
> > - return rescan_partitions(disk, bdev);
> > + if (disk_part_scan_enabled(disk))
> > + return rescan_partitions(disk, bdev);
> > + else // update size but not partitions, could be sr or sd
>
> ^^ /* Comment */
> > + return disk->fops->revalidate_disk(disk);
>
> and what happens if a device without ->revalidate_disk() defined calls into
> this
> function?
>
> > }
> > EXPORT_SYMBOL(__blkdev_reread_part);
> >
> > --
> > 2.16.1.72.g5be1f00
> >
>
> --
> Carlos
--
Carlos
