On Tue, Feb 12, 2019 at 09:57:17PM -0500, Martin K. Petersen wrote:
> Some devices come online in write protected state and switch to
> read-write once they are ready to process I/O requests. These devices
> broke with commit 20bd1d026aac ("scsi: sd: Keep disk read-only when
> re-reading partition") because we had no way to distinguish between a
> user decision to set a block_device read-only and the actual hardware
> device being write-protected.
>
> Because partitions are dropped and recreated on revalidate we are
> unable to persist any user-provided policy in hd_struct. Introduce a
> bitmap in struct gendisk to track the user configuration. This bitmap
> is updated when BLKROSET is called on a given disk or partition.
>
> A helper function, get_user_ro(), is provided to determine whether the
> ioctl has forced read-only state for a given block device. This helper
> is used by set_disk_ro() and add_partition() to ensure that both
> existing and newly created partitions will get the correct state.
>
> - If BLKROSET sets a whole disk device read-only, all partitions will
> now end up in a read-only state.
>
> - If BLKROSET sets a given partition read-only, that partition will
> remain read-only post revalidate.
>
> - Otherwise both the whole disk device and any partitions will
> reflect the write protect state of the underlying device.
>
> Cc: Jeremy Cline <jeremy@xxxxxxxxxx>
> Cc: Oleksii Kurochko <olkuroch@xxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # v4.16+
> Reported-by: Oleksii Kurochko <olkuroch@xxxxxxxxx>
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=201221
> Fixes: 20bd1d026aac ("scsi: sd: Keep disk read-only when re-reading partition")
> Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
>
> ---
>
> v2:
> - Track user read-only state in a bitmap
>
> - Work around the regression that caused us to drop user
> preferences on revalidate
> ---
> block/genhd.c | 22 +++++++++++++++++-----
> block/ioctl.c | 4 ++++
> block/partition-generic.c | 2 +-
> drivers/scsi/sd.c | 4 +---
> include/linux/genhd.h | 2 ++
> 5 files changed, 25 insertions(+), 9 deletions(-)
>
> diff --git a/block/genhd.c b/block/genhd.c
> index 1dd8fd6613b8..34667eb1d3cc 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -1544,19 +1544,31 @@ void set_device_ro(struct block_device *bdev, int flag)
>
> EXPORT_SYMBOL(set_device_ro);
>
> +bool get_user_ro(struct gendisk *disk, unsigned int partno)
> +{
> + /* Is the user read-only bit set for the whole disk device? */
> + if (test_bit(0, disk->user_ro_bitmap))
> + return true;
> +
> + /* Is the user read-only bit set for this particular partition? */
> + if (test_bit(partno, disk->user_ro_bitmap))
> + return true;
> +
> + return false;
> +}
> +EXPORT_SYMBOL(get_user_ro);
No need to export this function.
> + p->policy = get_user_ro(disk, partno) ?: get_disk_ro(disk);
Can we avoid the obsfucating non-standard (GNU extension) use of ?: here?
Just use a local variable and a good old if.
