Re: [PATCH 1/4] block: add a hard-readonly flag to struct gendisk

Hannes Reinecke
2020-11-30T07:56:44Z

On 11/29/20 7:19 PM, Christoph Hellwig wrote:
> 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 is used to set a whole-disk device read-only, any
> partitions will end up in a read-only state until the user
> explicitly clears the flag.
>
> - 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>
> ---
> block/blk-core.c | 2 +-
> block/genhd.c | 34 +++++++++++++++++++---------------
> block/partitions/core.c | 3 +--
> include/linux/genhd.h | 6 ++++--
> 4 files changed, 25 insertions(+), 20 deletions(-)
>
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
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