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Date: Sun, 25 Jun 2023 15:25:38 +0200
From: Milan Broz <gmazyland@...il.com>
To: Demi Marie Obenour <demi@...isiblethingslab.com>,
Alasdair Kergon <agk@...hat.com>,
Mike Snitzer <snitzer@...nel.org>, dm-devel@...hat.com
Cc: linux-kernel@...r.kernel.org
Subject: Re: [dm-devel] [PATCH v2 3/4] dm ioctl: Allow userspace to suppress
uevent generation
On 6/25/23 01:09, Demi Marie Obenour wrote:
> Userspace can use this to avoid spamming udev with events that udev
> should ignore.
Well, does it also mean that udev will not create /dev/disk/by-* symlinks
(as response to the change udev event followed by internal udev blkid scan)?
If it is a private device, that is ok. But for a visible device I think
that it breaks some assumptions in userspace (presence of symlinks mentioned
above etc).
So, what is the exact use for this patch?
Milan
>
> Signed-off-by: Demi Marie Obenour <demi@...isiblethingslab.com>
> ---
> drivers/md/dm-core.h | 2 +
> drivers/md/dm-ioctl.c | 71 ++++++++++++++++++-----------------
> drivers/md/dm.c | 5 ++-
> include/linux/device-mapper.h | 2 +-
> include/uapi/linux/dm-ioctl.h | 14 +++++--
> 5 files changed, 54 insertions(+), 40 deletions(-)
>
> diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h
> index 0d93661f88d306e0d0aa3a1ac085880a8b63d9d6..5a4acdbf119f9b3f9a1c60de36d23f0658449701 100644
> --- a/drivers/md/dm-core.h
> +++ b/drivers/md/dm-core.h
> @@ -115,6 +115,8 @@ struct mapped_device {
>
> /* for blk-mq request-based DM support */
> bool init_tio_pdu:1;
> + /* If set, do not emit any uevents. */
> + bool disable_uevents:1;
> struct blk_mq_tag_set *tag_set;
>
> struct dm_stats stats;
> diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> index 7abaeec33f1884d4588e8563fb02e9ea1a6782c8..7eab9a8c77ff3286346a1c44581d3b6370a731eb 100644
> --- a/drivers/md/dm-ioctl.c
> +++ b/drivers/md/dm-ioctl.c
> @@ -821,6 +821,11 @@ static struct dm_table *dm_get_live_or_inactive_table(struct mapped_device *md,
> dm_get_inactive_table(md, srcu_idx) : dm_get_live_table(md, srcu_idx);
> }
>
> +static inline bool sloppy_checks(const struct dm_ioctl *param)
> +{
> + return param->version[0] < DM_VERSION_MAJOR_STRICT;
> +}
> +
> /*
> * Fills in a dm_ioctl structure, ready for sending back to
> * userland.
> @@ -879,7 +884,7 @@ static void __dev_status(struct mapped_device *md, struct dm_ioctl *param)
> dm_put_live_table(md, srcu_idx);
> }
>
> - if (param->version[0] >= DM_VERSION_MAJOR_STRICT)
> + if (!sloppy_checks(param))
> dm_set_diskseq(param, disk->diskseq);
> }
>
> @@ -895,7 +900,7 @@ static int dev_create(struct file *filp, struct dm_ioctl *param, size_t param_si
> if (param->flags & DM_PERSISTENT_DEV_FLAG)
> m = MINOR(huge_decode_dev(param->dev));
>
> - r = dm_create(m, &md);
> + r = dm_create(m, &md, param->flags & DM_DISABLE_UEVENTS_FLAG);
> if (r)
> return r;
>
> @@ -1463,11 +1468,6 @@ static int next_target(struct dm_target_spec *last, uint32_t next, const char *e
> return 0;
> }
>
> -static inline bool sloppy_checks(const struct dm_ioctl *param)
> -{
> - return param->version[0] < DM_VERSION_MAJOR_STRICT;
> -}
> -
> static bool no_non_nul_after_nul(const char *untrusted_str, size_t size,
> unsigned int cmd, const char *msg)
> {
> @@ -1939,64 +1939,67 @@ static int target_message(struct file *filp, struct dm_ioctl *param, size_t para
> * Implementation of open/close/ioctl on the special char device.
> *---------------------------------------------------------------
> */
> -static ioctl_fn lookup_ioctl(unsigned int cmd, int *ioctl_flags, uint32_t *supported_flags)
> +static ioctl_fn lookup_ioctl(unsigned int cmd, bool strict, int *ioctl_flags,
> + uint32_t *supported_flags)
> {
> static const struct {
> int cmd;
> int flags;
> ioctl_fn fn;
> uint32_t supported_flags;
> + uint32_t strict_flags;
> } _ioctls[] = {
> /* Macro to make the structure initializers somewhat readable */
> -#define I(cmd, flags, fn, supported_flags) ((typeof(_ioctls[0])) { \
> +#define I(cmd, flags, fn, supported_flags, strict_flags) ((typeof(_ioctls[0])) { \
> (cmd), \
> (flags), \
> (fn), \
> /*
> * Supported flags in sloppy mode must not include anything in DM_STRICT_ONLY_FLAGS.
> - * Use BUILD_BUG_ON_ZERO to check for that. Currently there are no strict-only flags
> - * defined.
> + * Use BUILD_BUG_ON_ZERO to check for that.
> */ \
> (supported_flags) | BUILD_BUG_ON_ZERO((supported_flags) & DM_STRICT_ONLY_FLAGS), \
> + (strict_flags) | (supported_flags) | \
> + BUILD_BUG_ON_ZERO((supported_flags) & (strict_flags)), \
> })
> - I(DM_VERSION_CMD, 0, NULL, 0), /* version is dealt with elsewhere */
> + I(DM_VERSION_CMD, 0, NULL, 0, 0), /* version is dealt with elsewhere */
> I(DM_REMOVE_ALL_CMD, IOCTL_FLAGS_NO_PARAMS | IOCTL_FLAGS_ISSUE_GLOBAL_EVENT,
> - remove_all, DM_DEFERRED_REMOVE),
> - I(DM_LIST_DEVICES_CMD, 0, list_devices, DM_UUID_FLAG),
> + remove_all, DM_DEFERRED_REMOVE, 0),
> + I(DM_LIST_DEVICES_CMD, 0, list_devices, DM_UUID_FLAG, 0),
> I(DM_DEV_CREATE_CMD, IOCTL_FLAGS_NO_PARAMS | IOCTL_FLAGS_ISSUE_GLOBAL_EVENT,
> - dev_create, DM_PERSISTENT_DEV_FLAG),
> + dev_create, DM_PERSISTENT_DEV_FLAG, DM_DISABLE_UEVENTS_FLAG),
> I(DM_DEV_REMOVE_CMD, IOCTL_FLAGS_NO_PARAMS | IOCTL_FLAGS_ISSUE_GLOBAL_EVENT,
> - dev_remove, DM_DEFERRED_REMOVE),
> + dev_remove, DM_DEFERRED_REMOVE, 0),
> I(DM_DEV_RENAME_CMD, IOCTL_FLAGS_ISSUE_GLOBAL_EVENT, dev_rename,
> - DM_QUERY_INACTIVE_TABLE_FLAG | DM_UUID_FLAG),
> + DM_QUERY_INACTIVE_TABLE_FLAG | DM_UUID_FLAG, 0),
> I(DM_DEV_SUSPEND_CMD, IOCTL_FLAGS_NO_PARAMS, dev_suspend,
> - DM_QUERY_INACTIVE_TABLE_FLAG | DM_SUSPEND_FLAG | DM_SKIP_LOCKFS_FLAG |
> - DM_NOFLUSH_FLAG),
> + DM_QUERY_INACTIVE_TABLE_FLAG | DM_SUSPEND_FLAG |
> + DM_SKIP_LOCKFS_FLAG | DM_NOFLUSH_FLAG, 0),
> I(DM_DEV_STATUS_CMD, IOCTL_FLAGS_NO_PARAMS, dev_status,
> - DM_QUERY_INACTIVE_TABLE_FLAG),
> + DM_QUERY_INACTIVE_TABLE_FLAG, 0),
> I(DM_DEV_WAIT_CMD, IOCTL_FLAGS_TAKES_EVENT_NR, dev_wait,
> - DM_QUERY_INACTIVE_TABLE_FLAG | DM_STATUS_TABLE_FLAG | DM_NOFLUSH_FLAG),
> - I(DM_TABLE_LOAD_CMD, 0, table_load, DM_QUERY_INACTIVE_TABLE_FLAG |
> - DM_READONLY_FLAG),
> + DM_QUERY_INACTIVE_TABLE_FLAG | DM_STATUS_TABLE_FLAG | DM_NOFLUSH_FLAG, 0),
> + I(DM_TABLE_LOAD_CMD, 0, table_load,
> + DM_QUERY_INACTIVE_TABLE_FLAG | DM_READONLY_FLAG, 0),
> I(DM_TABLE_CLEAR_CMD, IOCTL_FLAGS_NO_PARAMS, table_clear,
> - DM_QUERY_INACTIVE_TABLE_FLAG),
> - I(DM_TABLE_DEPS_CMD, 0, table_deps, DM_QUERY_INACTIVE_TABLE_FLAG),
> + DM_QUERY_INACTIVE_TABLE_FLAG, 0),
> + I(DM_TABLE_DEPS_CMD, 0, table_deps, DM_QUERY_INACTIVE_TABLE_FLAG, 0),
> I(DM_TABLE_STATUS_CMD, 0, table_status,
> - DM_QUERY_INACTIVE_TABLE_FLAG | DM_STATUS_TABLE_FLAG | DM_NOFLUSH_FLAG),
> + DM_QUERY_INACTIVE_TABLE_FLAG | DM_STATUS_TABLE_FLAG | DM_NOFLUSH_FLAG, 0),
>
> - I(DM_LIST_VERSIONS_CMD, 0, list_versions, 0),
> + I(DM_LIST_VERSIONS_CMD, 0, list_versions, 0, 0),
>
> - I(DM_TARGET_MSG_CMD, 0, target_message, DM_QUERY_INACTIVE_TABLE_FLAG),
> - I(DM_DEV_SET_GEOMETRY_CMD, 0, dev_set_geometry, 0),
> - I(DM_DEV_ARM_POLL_CMD, IOCTL_FLAGS_NO_PARAMS, dev_arm_poll, 0),
> - I(DM_GET_TARGET_VERSION_CMD, 0, get_target_version, 0),
> + I(DM_TARGET_MSG_CMD, 0, target_message, DM_QUERY_INACTIVE_TABLE_FLAG, 0),
> + I(DM_DEV_SET_GEOMETRY_CMD, 0, dev_set_geometry, 0, 0),
> + I(DM_DEV_ARM_POLL_CMD, IOCTL_FLAGS_NO_PARAMS, dev_arm_poll, 0, 0),
> + I(DM_GET_TARGET_VERSION_CMD, 0, get_target_version, 0, 0),
> };
>
> if (unlikely(cmd >= ARRAY_SIZE(_ioctls)))
> return NULL;
>
> cmd = array_index_nospec(cmd, ARRAY_SIZE(_ioctls));
> - *supported_flags = _ioctls[cmd].supported_flags;
> + *supported_flags = strict ? _ioctls[cmd].strict_flags : _ioctls[cmd].supported_flags;
> *ioctl_flags = _ioctls[cmd].flags;
> return _ioctls[cmd].fn;
> }
> @@ -2260,7 +2263,7 @@ static int ctl_ioctl(struct file *file, uint command, struct dm_ioctl __user *us
> if (cmd == DM_VERSION_CMD)
> return 0;
>
> - fn = lookup_ioctl(cmd, &ioctl_flags, &supported_flags);
> + fn = lookup_ioctl(cmd, !sloppy_checks(¶m_kernel), &ioctl_flags, &supported_flags);
> if (!fn) {
> DMERR("dm_ctl_ioctl: unknown command 0x%x", command);
> return -ENOTTY;
> @@ -2480,7 +2483,7 @@ int __init dm_early_create(struct dm_ioctl *dmi,
> m = MINOR(huge_decode_dev(dmi->dev));
>
> /* alloc dm device */
> - r = dm_create(m, &md);
> + r = dm_create(m, &md, false);
> if (r)
> return r;
>
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index ea1671c39ba131ab2e49b93289d1094cda5cfb25..b7817b4aea52033afeeea9f2b93b9215de682e9c 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -2281,13 +2281,14 @@ static struct dm_table *__unbind(struct mapped_device *md)
> /*
> * Constructor for a new device.
> */
> -int dm_create(int minor, struct mapped_device **result)
> +int dm_create(int minor, struct mapped_device **result, bool disable_uevents)
> {
> struct mapped_device *md;
>
> md = alloc_dev(minor);
> if (!md)
> return -ENXIO;
> + md->disable_uevents = disable_uevents;
>
> dm_ima_reset_data(md);
>
> @@ -3005,6 +3006,8 @@ int dm_kobject_uevent(struct mapped_device *md, enum kobject_action action,
> char udev_cookie[DM_COOKIE_LENGTH];
> char *envp[3] = { NULL, NULL, NULL };
> char **envpp = envp;
> + if (md->disable_uevents)
> + return 0;
> if (cookie) {
> snprintf(udev_cookie, DM_COOKIE_LENGTH, "%s=%u",
> DM_COOKIE_ENV_VAR_NAME, cookie);
> diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
> index 69d0435c7ebb0d7b712e2b8bf32d9ba34c54e09e..2be940c2c6f42ed8e13b97ea8b07d0895566f3e2 100644
> --- a/include/linux/device-mapper.h
> +++ b/include/linux/device-mapper.h
> @@ -461,7 +461,7 @@ void dm_consume_args(struct dm_arg_set *as, unsigned int num_args);
> * DM_ANY_MINOR chooses the next available minor number.
> */
> #define DM_ANY_MINOR (-1)
> -int dm_create(int minor, struct mapped_device **md);
> +int dm_create(int minor, struct mapped_device **md, bool disable_uevents);
>
> /*
> * Reference counting for md.
> diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h
> index 1d33109aece2ff9854e752066baa96fdf7d85857..b338a4f9a299acda9430995d63fbb490e70c8cd8 100644
> --- a/include/uapi/linux/dm-ioctl.h
> +++ b/include/uapi/linux/dm-ioctl.h
> @@ -369,8 +369,16 @@ enum {
> #define DM_BUFFER_FULL_FLAG (1 << 8) /* Out */
>
> /*
> - * This flag is now ignored if DM_VERSION_MAJOR is used, and causes
> - * -EINVAL if DM_VERSION_MAJOR_STRICT is used.
> + * This flag is only recognized when DM_VERSION_MAJOR_STRICT is used.
> + * It tells the kernel to not generate any uevents for the newly-created
> + * device. Using it outside of DM_DEV_CREATE results in -EINVAL. When
> + * DM_VERSION_MAJOR is used this flag is ignored.
> + */
> +#define DM_DISABLE_UEVENTS_FLAG (1 << 9) /* In */
> +
> +/*
> + * This flag is now ignored if DM_VERSION_MAJOR is used. When
> + * DM_VERSION_MAJOR_STRICT is used it is an alias for DM_DISABLE_UEVENT_FLAG.
> */
> #define DM_SKIP_BDGET_FLAG (1 << 9) /* In */
>
> @@ -439,8 +447,6 @@ enum {
>
> /*
> * If DM_VERSION_MAJOR is used, these flags are ignored by the kernel.
> - * If DM_VERSION_MAJOR_STRICT is used, these flags are reserved and
> - * must be zeroed.
> */
> #define DM_STRICT_ONLY_FLAGS \
> (DM_ACTIVE_PRESENT_FLAG | DM_INACTIVE_PRESENT_FLAG | \
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