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Message-ID: <f7b1688f2a17165ff5bfee7cc892c0067af7a9ca.camel@suse.com>
Date: Thu, 08 May 2025 15:50:13 +0200
From: Martin Wilck <mwilck@...e.com>
To: Kevin Wolf <kwolf@...hat.com>, dm-devel@...ts.linux.dev
Cc: hreitz@...hat.com, mpatocka@...hat.com, snitzer@...nel.org,
bmarzins@...hat.com, linux-kernel@...r.kernel.org, Hannes Reinecke
<hare@...e.com>
Subject: Re: [PATCH 1/2] dm: Allow .prepare_ioctl to handle ioctls directly
On Tue, 2025-04-29 at 18:50 +0200, Kevin Wolf wrote:
> This adds a 'bool *forward' parameter to .prepare_ioctl, which allows
> device mapper targets to accept ioctls to themselves instead of the
> underlying device. If the target already fully handled the ioctl, it
> sets *forward to false and device mapper won't forward it to the
> underlying device any more.
>
> In order for targets to actually know what the ioctl is about and how
> to
> handle it, pass also cmd and arg.
>
> As long as targets restrict themselves to interpreting ioctls of type
> DM_IOCTL, this is a backwards compatible change because previously,
> any
> such ioctl would have been passed down through all device mapper
> layers
> until it reached a device that can't understand the ioctl and would
> return an error.
>
> Signed-off-by: Kevin Wolf <kwolf@...hat.com>
> ---
> include/linux/device-mapper.h | 9 ++++++++-
> drivers/md/dm-dust.c | 4 +++-
> drivers/md/dm-ebs-target.c | 3 ++-
> drivers/md/dm-flakey.c | 4 +++-
> drivers/md/dm-linear.c | 4 +++-
> drivers/md/dm-log-writes.c | 4 +++-
> drivers/md/dm-mpath.c | 4 +++-
> drivers/md/dm-switch.c | 4 +++-
> drivers/md/dm-verity-target.c | 4 +++-
> drivers/md/dm-zoned-target.c | 3 ++-
> drivers/md/dm.c | 17 +++++++++++------
> 11 files changed, 44 insertions(+), 16 deletions(-)
>
> diff --git a/include/linux/device-mapper.h b/include/linux/device-
> mapper.h
> index bcc6d7b69470..cb95951547ab 100644
> --- a/include/linux/device-mapper.h
> +++ b/include/linux/device-mapper.h
> @@ -93,7 +93,14 @@ typedef void (*dm_status_fn) (struct dm_target
> *ti, status_type_t status_type,
> typedef int (*dm_message_fn) (struct dm_target *ti, unsigned int
> argc, char **argv,
> char *result, unsigned int maxlen);
>
> -typedef int (*dm_prepare_ioctl_fn) (struct dm_target *ti, struct
> block_device **bdev);
> +/*
> + * Called with *forward == true. If it remains true, the ioctl
> should be
> + * forwarded to bdev. If it is reset to false, the target already
> fully handled
> + * the ioctl and the return value is the return value for the whole
> ioctl.
> + */
> +typedef int (*dm_prepare_ioctl_fn) (struct dm_target *ti, struct
> block_device **bdev,
> + unsigned int cmd, unsigned long arg,
> + bool *forward);
>
> #ifdef CONFIG_BLK_DEV_ZONED
> typedef int (*dm_report_zones_fn) (struct dm_target *ti,
> diff --git a/drivers/md/dm-dust.c b/drivers/md/dm-dust.c
> index 1a33820c9f46..e75310232bbf 100644
> --- a/drivers/md/dm-dust.c
> +++ b/drivers/md/dm-dust.c
> @@ -534,7 +534,9 @@ static void dust_status(struct dm_target *ti,
> status_type_t type,
> }
> }
>
> -static int dust_prepare_ioctl(struct dm_target *ti, struct
> block_device **bdev)
> +static int dust_prepare_ioctl(struct dm_target *ti, struct
> block_device **bdev,
> + unsigned int cmd, unsigned long arg,
> + bool *forward)
> {
> struct dust_device *dd = ti->private;
> struct dm_dev *dev = dd->dev;
> diff --git a/drivers/md/dm-ebs-target.c b/drivers/md/dm-ebs-target.c
> index b19b0142a690..6abb31ca9662 100644
> --- a/drivers/md/dm-ebs-target.c
> +++ b/drivers/md/dm-ebs-target.c
> @@ -415,7 +415,8 @@ static void ebs_status(struct dm_target *ti,
> status_type_t type,
> }
> }
>
> -static int ebs_prepare_ioctl(struct dm_target *ti, struct
> block_device **bdev)
> +static int ebs_prepare_ioctl(struct dm_target *ti, struct
> block_device **bdev,
> + unsigned int cmd, unsigned long arg, bool *forward)
> {
> struct ebs_c *ec = ti->private;
> struct dm_dev *dev = ec->dev;
> diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c
> index b690905ab89f..0fceb08f4622 100644
> --- a/drivers/md/dm-flakey.c
> +++ b/drivers/md/dm-flakey.c
> @@ -638,7 +638,9 @@ static void flakey_status(struct dm_target *ti,
> status_type_t type,
> }
> }
>
> -static int flakey_prepare_ioctl(struct dm_target *ti, struct
> block_device **bdev)
> +static int flakey_prepare_ioctl(struct dm_target *ti, struct
> block_device **bdev,
> + unsigned int cmd, unsigned long arg,
> + bool *forward)
> {
> struct flakey_c *fc = ti->private;
>
> diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
> index 66318aba4bdb..15538ec58f8e 100644
> --- a/drivers/md/dm-linear.c
> +++ b/drivers/md/dm-linear.c
> @@ -119,7 +119,9 @@ static void linear_status(struct dm_target *ti,
> status_type_t type,
> }
> }
>
> -static int linear_prepare_ioctl(struct dm_target *ti, struct
> block_device **bdev)
> +static int linear_prepare_ioctl(struct dm_target *ti, struct
> block_device **bdev,
> + unsigned int cmd, unsigned long arg,
> + bool *forward)
> {
> struct linear_c *lc = ti->private;
> struct dm_dev *dev = lc->dev;
> diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c
> index 8d7df8303d0a..d484e8e1d48a 100644
> --- a/drivers/md/dm-log-writes.c
> +++ b/drivers/md/dm-log-writes.c
> @@ -818,7 +818,9 @@ static void log_writes_status(struct dm_target
> *ti, status_type_t type,
> }
>
> static int log_writes_prepare_ioctl(struct dm_target *ti,
> - struct block_device **bdev)
> + struct block_device **bdev,
> + unsigned int cmd, unsigned long arg,
> + bool *forward)
> {
> struct log_writes_c *lc = ti->private;
> struct dm_dev *dev = lc->dev;
> diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
> index 6c98f4ae5ea9..909ed6890ba5 100644
> --- a/drivers/md/dm-mpath.c
> +++ b/drivers/md/dm-mpath.c
> @@ -2022,7 +2022,9 @@ static int multipath_message(struct dm_target
> *ti, unsigned int argc, char **arg
> }
>
> static int multipath_prepare_ioctl(struct dm_target *ti,
> - struct block_device **bdev)
> + struct block_device **bdev,
> + unsigned int cmd, unsigned long arg,
> + bool *forward)
> {
> struct multipath *m = ti->private;
> struct pgpath *pgpath;
> diff --git a/drivers/md/dm-switch.c b/drivers/md/dm-switch.c
> index dfd9fb52a6f3..bb1a70b5a215 100644
> --- a/drivers/md/dm-switch.c
> +++ b/drivers/md/dm-switch.c
> @@ -517,7 +517,9 @@ static void switch_status(struct dm_target *ti,
> status_type_t type,
> *
> * Passthrough all ioctls to the path for sector 0
> */
> -static int switch_prepare_ioctl(struct dm_target *ti, struct
> block_device **bdev)
> +static int switch_prepare_ioctl(struct dm_target *ti, struct
> block_device **bdev,
> + unsigned int cmd, unsigned long arg,
> + bool *forward)
> {
> struct switch_ctx *sctx = ti->private;
> unsigned int path_nr;
> diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-
> target.c
> index 4de2c226ac9d..34a9f9fbd0d1 100644
> --- a/drivers/md/dm-verity-target.c
> +++ b/drivers/md/dm-verity-target.c
> @@ -994,7 +994,9 @@ static void verity_status(struct dm_target *ti,
> status_type_t type,
> }
> }
>
> -static int verity_prepare_ioctl(struct dm_target *ti, struct
> block_device **bdev)
> +static int verity_prepare_ioctl(struct dm_target *ti, struct
> block_device **bdev,
> + unsigned int cmd, unsigned long arg,
> + bool *forward)
> {
> struct dm_verity *v = ti->private;
>
> diff --git a/drivers/md/dm-zoned-target.c b/drivers/md/dm-zoned-
> target.c
> index 6141fc25d842..5da3db06da10 100644
> --- a/drivers/md/dm-zoned-target.c
> +++ b/drivers/md/dm-zoned-target.c
> @@ -1015,7 +1015,8 @@ static void dmz_io_hints(struct dm_target *ti,
> struct queue_limits *limits)
> /*
> * Pass on ioctl to the backend device.
> */
> -static int dmz_prepare_ioctl(struct dm_target *ti, struct
> block_device **bdev)
> +static int dmz_prepare_ioctl(struct dm_target *ti, struct
> block_device **bdev,
> + unsigned int cmd, unsigned long arg, bool *forward)
> {
> struct dmz_target *dmz = ti->private;
> struct dmz_dev *dev = &dmz->dev[0];
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index ccccc098b30e..1726f0f828cc 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -411,7 +411,8 @@ static int dm_blk_getgeo(struct block_device
> *bdev, struct hd_geometry *geo)
> }
>
> static int dm_prepare_ioctl(struct mapped_device *md, int *srcu_idx,
> - struct block_device **bdev)
> + struct block_device **bdev, unsigned int cmd,
> + unsigned long arg, bool *forward)
> {
> struct dm_target *ti;
> struct dm_table *map;
> @@ -434,8 +435,8 @@ static int dm_prepare_ioctl(struct mapped_device
> *md, int *srcu_idx,
> if (dm_suspended_md(md))
> return -EAGAIN;
>
> - r = ti->type->prepare_ioctl(ti, bdev);
> - if (r == -ENOTCONN && !fatal_signal_pending(current)) {
> + r = ti->type->prepare_ioctl(ti, bdev, cmd, arg, forward);
> + if (r == -ENOTCONN && *forward && !fatal_signal_pending(current)) {
> dm_put_live_table(md, *srcu_idx);
> fsleep(10000);
> goto retry;
> @@ -454,9 +455,10 @@ static int dm_blk_ioctl(struct block_device
> *bdev, blk_mode_t mode,
> {
> struct mapped_device *md = bdev->bd_disk->private_data;
> int r, srcu_idx;
> + bool forward = true;
>
> - r = dm_prepare_ioctl(md, &srcu_idx, &bdev);
> - if (r < 0)
> + r = dm_prepare_ioctl(md, &srcu_idx, &bdev, cmd, arg, &forward);
> + if (!forward || r < 0)
> goto out;
>
> if (r > 0) {
> @@ -3630,10 +3632,13 @@ static int dm_pr_clear(struct block_device
> *bdev, u64 key)
> struct mapped_device *md = bdev->bd_disk->private_data;
> const struct pr_ops *ops;
> int r, srcu_idx;
> + bool forward = true;
>
> - r = dm_prepare_ioctl(md, &srcu_idx, &bdev);
> + /* Not a real ioctl, but targets must not interpret non-DM ioctls
> */
> + r = dm_prepare_ioctl(md, &srcu_idx, &bdev, 0, 0, &forward);
> if (r < 0)
> goto out;
> + WARN_ON_ONCE(!forward);
>
> ops = bdev->bd_disk->fops->pr_ops;
> if (ops && ops->pr_clear)
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