block: add a hard-readonly flag to struct gendisk

Commit 20bd1d026aac ("scsi: sd: Keep disk read-only when re-reading
partition") addressed a long-standing problem with user read-only
policy being overridden as a result of a device-initiated revalidate.
The commit has since been reverted due to a regression that left some
USB devices read-only indefinitely.

To fix the underlying problems with revalidate we need to keep track
of hardware state and user policy separately.

The gendisk has been updated to reflect the current hardware state set
by the device driver. This is done to allow returning the device to
the hardware state once the user clears the BLKROSET flag.

The resulting semantics are as follows:

 - If BLKROSET sets a given partition read-only, that partition will
   remain read-only even if the underlying storage stack initiates a
   revalidate. However, the BLKRRPART ioctl will cause the partition
   table to be dropped and any user policy on partitions will be lost.

 - If BLKROSET has not been set, both the whole disk device and any
   partitions will reflect the current write-protect state of the
   underlying device.

Based on a patch from Martin K. Petersen <martin.petersen@oracle.com>.

Reported-by: Oleksii Kurochko <olkuroch@cisco.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=201221
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-core.c b/block/blk-core.c
index 7663a9b94b8002ad710231ec726dfd4cc7c23513..08ff8ca325296ec558ad834050710bbd0de87cdd 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -694,9 +694,7 @@ static inline bool should_fail_request(struct block_device *part,
 
 static inline bool bio_check_ro(struct bio *bio, struct block_device *part)
 {
-       const int op = bio_op(bio);
-
-       if (part->bd_read_only && op_is_write(op)) {
+       if (op_is_write(bio_op(bio)) && bdev_read_only(part)) {
                char b[BDEVNAME_SIZE];
 
                if (op_is_flush(bio->bi_opf) && !bio_sectors(bio))

diff --git a/block/genhd.c b/block/genhd.c
index 484a474648d5b29b74bc3232fc96269c0791e4ee..1873e457132823cf445c1a1d93f539699381797b 100644 (file)
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1637,27 +1637,32 @@ static void set_disk_ro_uevent(struct gendisk *gd, int ro)
        kobject_uevent_env(&disk_to_dev(gd)->kobj, KOBJ_CHANGE, envp);
 }
 
-void set_disk_ro(struct gendisk *disk, int flag)
+/**
+ * set_disk_ro - set a gendisk read-only
+ * @disk:      gendisk to operate on
+ * @ready_only:        %true to set the disk read-only, %false set the disk read/write
+ *
+ * This function is used to indicate whether a given disk device should have its
+ * read-only flag set. set_disk_ro() is typically used by device drivers to
+ * indicate whether the underlying physical device is write-protected.
+ */
+void set_disk_ro(struct gendisk *disk, bool read_only)
 {
-       struct disk_part_iter piter;
-       struct block_device *part;
-
-       if (disk->part0->bd_read_only != flag) {
-               set_disk_ro_uevent(disk, flag);
-               disk->part0->bd_read_only = flag;
+       if (read_only) {
+               if (test_and_set_bit(GD_READ_ONLY, &disk->state))
+                       return;
+       } else {
+               if (!test_and_clear_bit(GD_READ_ONLY, &disk->state))
+                       return;
        }
-
-       disk_part_iter_init(&piter, disk, DISK_PITER_INCL_EMPTY);
-       while ((part = disk_part_iter_next(&piter)))
-               part->bd_read_only = flag;
-       disk_part_iter_exit(&piter);
+       set_disk_ro_uevent(disk, read_only);
 }
-
 EXPORT_SYMBOL(set_disk_ro);
 
 int bdev_read_only(struct block_device *bdev)
 {
-       return bdev->bd_read_only;
+       return bdev->bd_read_only ||
+               test_bit(GD_READ_ONLY, &bdev->bd_disk->state);
 }
 EXPORT_SYMBOL(bdev_read_only);
 

diff --git a/block/partitions/core.c b/block/partitions/core.c
index e7d776db803b12f7e784235a20fdc5989cbe6cc6..168d5906077cfd8c71e5909c3afb0f2efc49d133 100644 (file)
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -195,7 +195,7 @@ static ssize_t part_start_show(struct device *dev,
 static ssize_t part_ro_show(struct device *dev,
                            struct device_attribute *attr, char *buf)
 {
-       return sprintf(buf, "%d\n", dev_to_bdev(dev)->bd_read_only);
+       return sprintf(buf, "%d\n", bdev_read_only(dev_to_bdev(dev)));
 }
 
 static ssize_t part_alignment_offset_show(struct device *dev,
@@ -361,7 +361,6 @@ static struct block_device *add_partition(struct gendisk *disk, int partno,
 
        bdev->bd_start_sect = start;
        bdev_set_nr_sectors(bdev, len);
-       bdev->bd_read_only = get_disk_ro(disk);
 
        if (info) {
                err = -ENOMEM;

diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 809aaa32d53cbad90731b53db0c62bda6d6bda49..a62ccbfac54b483af396c3a2d9b3ccace271d48c 100644 (file)
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -163,6 +163,7 @@ struct gendisk {
        int flags;
        unsigned long state;
 #define GD_NEED_PART_SCAN              0
+#define GD_READ_ONLY                   1
        struct kobject *slave_dir;
 
        struct timer_rand_state *random;
@@ -249,11 +250,12 @@ static inline void add_disk_no_queue_reg(struct gendisk *disk)
 extern void del_gendisk(struct gendisk *gp);
 extern struct block_device *bdget_disk(struct gendisk *disk, int partno);
 
-extern void set_disk_ro(struct gendisk *disk, int flag);
+void set_disk_ro(struct gendisk *disk, bool read_only);
 
 static inline int get_disk_ro(struct gendisk *disk)
 {
-       return disk->part0->bd_read_only;
+       return disk->part0->bd_read_only ||
+               test_bit(GD_READ_ONLY, &disk->state);
 }
 
 extern void disk_block_events(struct gendisk *disk);