Hi
>I'd like to ask why is this patch needed? Why do you want to set read-only
>status using this ioctl instead of using the existing table flag?
I basically just wanted to be able to use `blockdev --setrw {}` on
Android for a block device that had its table mapped as read only. I
believe that used to work on 5.10 or so, but not anymore.
>If this is needed, we need to add another flag that is being set by
>dm_blk_set_read_only, so that dm_blk_set_read_only and dm_resume won't
>step over each other's changes.
The following diff should address that, however I noticed that
set_disk_ro() itself, triggers an uevent message that makes upstream
lvm2/udev/10-dm.rules.in <http://10-dm.rules.in> disable a dm device, so
not sure if this is
good to have, after all.
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -412,6 +412,19 @@ static int dm_blk_getgeo(struct block_device *bdev, struct hd_geometry *geo)
static int dm_blk_set_read_only(struct block_device *bdev, bool ro)
{
+ struct mapped_device *md = bdev->bd_disk->private_data;
+ int srcu_idx;
+ struct dm_table *table;
+
+ table = dm_get_live_table(md, &srcu_idx);
+ if (table) {
+ if (ro)
+ table->mode &= ~BLK_OPEN_WRITE;
+ else
+ table->mode = ~BLK_OPEN_WRITE;
+ }
+ dm_put_live_table(md, srcu_idx);
+
set_disk_ro(bdev->bd_disk, ro);
return 0;
}
On Tue, Aug 27, 2024 at 7:52 PM Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote:
On Wed, 21 Aug 2024, Łukasz Patron wrote:
> This lets us change the read-only flag for device mapper block
devices
> via the BLKROSET ioctl.
>
> Signed-off-by: Łukasz Patron <priv.luk@xxxxxxxxx>
> ---
> drivers/md/dm.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 87bb90303435..538a93e596d7 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -410,6 +410,12 @@ static int dm_blk_getgeo(struct block_device
*bdev, struct hd_geometry *geo)
> return dm_get_geometry(md, geo);
> }
>
> +static int dm_blk_set_read_only(struct block_device *bdev, bool ro)
> +{
> + set_disk_ro(bdev->bd_disk, ro);
> + return 0;
> +}
> +
> static int dm_prepare_ioctl(struct mapped_device *md, int *srcu_idx,
> struct block_device **bdev)
> {
> @@ -3666,6 +3672,7 @@ static const struct block_device_operations
dm_blk_dops = {
> .release = dm_blk_close,
> .ioctl = dm_blk_ioctl,
> .getgeo = dm_blk_getgeo,
> + .set_read_only = dm_blk_set_read_only,
> .report_zones = dm_blk_report_zones,
> .pr_ops = &dm_pr_ops,
> .owner = THIS_MODULE
> --
> 2.46.0
Hi
Device mapper already calls set_disk_ro in the do_resume function.
So, the
problem here is that the value set using set_read_only will be
overwritten
as soon as a new table will be loaded.
I'd like to ask why is this patch needed? Why do you want to set
read-only
status using this ioctl instead of using the existing table flag?
If this is needed, we need to add another flag that is being set by
dm_blk_set_read_only, so that dm_blk_set_read_only and dm_resume won't
step over each other's changes.
Mikulas
