Christoph? Jens?
> 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);
> +
> void set_disk_ro(struct gendisk *disk, int flag)
> {
> struct disk_part_iter piter;
> struct hd_struct *part;
>
> - if (disk->part0.policy != flag) {
> + if (disk->part0.policy != flag)
> set_disk_ro_uevent(disk, flag);
> - disk->part0.policy = flag;
> - }
>
> - disk_part_iter_init(&piter, disk, DISK_PITER_INCL_EMPTY);
> + disk_part_iter_init(&piter, disk, DISK_PITER_INCL_EMPTY_PART0);
> while ((part = disk_part_iter_next(&piter)))
> - part->policy = flag;
> + part->policy = get_user_ro(disk, part->partno) ?: flag;
> disk_part_iter_exit(&piter);
> }
>
> diff --git a/block/ioctl.c b/block/ioctl.c
> index 4825c78a6baa..41206df89485 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -451,6 +451,10 @@ static int blkdev_roset(struct block_device *bdev, fmode_t mode,
> return ret;
> if (get_user(n, (int __user *)arg))
> return -EFAULT;
> + if (n)
> + set_bit(bdev->bd_partno, bdev->bd_disk->user_ro_bitmap);
> + else
> + clear_bit(bdev->bd_partno, bdev->bd_disk->user_ro_bitmap);
> set_device_ro(bdev, n);
> return 0;
> }
> diff --git a/block/partition-generic.c b/block/partition-generic.c
> index 8e596a8dff32..c6a3c21c2496 100644
> --- a/block/partition-generic.c
> +++ b/block/partition-generic.c
> @@ -338,7 +338,7 @@ struct hd_struct *add_partition(struct gendisk *disk, int partno,
> queue_limit_discard_alignment(&disk->queue->limits, start);
> p->nr_sects = len;
> p->partno = partno;
> - p->policy = get_disk_ro(disk);
> + p->policy = get_user_ro(disk, partno) ?: get_disk_ro(disk);
>
> if (info) {
> struct partition_meta_info *pinfo = alloc_part_info(disk);
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index 67cc439b86e4..5dfe37b08d3b 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -2591,10 +2591,8 @@ sd_read_write_protect_flag(struct scsi_disk *sdkp, unsigned char *buffer)
> int res;
> struct scsi_device *sdp = sdkp->device;
> struct scsi_mode_data data;
> - int disk_ro = get_disk_ro(sdkp->disk);
> int old_wp = sdkp->write_prot;
>
> - set_disk_ro(sdkp->disk, 0);
> if (sdp->skip_ms_page_3f) {
> sd_first_printk(KERN_NOTICE, sdkp, "Assuming Write Enabled\n");
> return;
> @@ -2632,7 +2630,7 @@ sd_read_write_protect_flag(struct scsi_disk *sdkp, unsigned char *buffer)
> "Test WP failed, assume Write Enabled\n");
> } else {
> sdkp->write_prot = ((data.device_specific & 0x80) != 0);
> - set_disk_ro(sdkp->disk, sdkp->write_prot || disk_ro);
> + set_disk_ro(sdkp->disk, sdkp->write_prot);
> if (sdkp->first_scan || old_wp != sdkp->write_prot) {
> sd_printk(KERN_NOTICE, sdkp, "Write Protect is %s\n",
> sdkp->write_prot ? "on" : "off");
> diff --git a/include/linux/genhd.h b/include/linux/genhd.h
> index 06c0fd594097..9645c2604465 100644
> --- a/include/linux/genhd.h
> +++ b/include/linux/genhd.h
> @@ -194,6 +194,7 @@ struct gendisk {
> */
> struct disk_part_tbl __rcu *part_tbl;
> struct hd_struct part0;
> + DECLARE_BITMAP(user_ro_bitmap, DISK_MAX_PARTS);
>
> const struct block_device_operations *fops;
> struct request_queue *queue;
> @@ -433,6 +434,7 @@ extern struct block_device *bdget_disk(struct gendisk *disk, int partno);
>
> extern void set_device_ro(struct block_device *bdev, int flag);
> extern void set_disk_ro(struct gendisk *disk, int flag);
> +extern bool get_user_ro(struct gendisk *disk, unsigned int partno);
>
> static inline int get_disk_ro(struct gendisk *disk)
> {
--
Martin K. Petersen Oracle Linux Engineering
