From: Lukas Prediger <lumip@xxxxxxxx> The current implementation of the CDROM_MEDIA_CHANGED ioctl relies on global state, meaning that only one process can detect a disc change while the ioctl call will return 0 for other calling processes afterwards (see bug 213267). This introduces a new cdrom ioctl, CDROM_TIMED_MEDIA_CHANGE, that works by maintaining a timestamp of the last detected disc change instead of a boolean flag: Processes calling this ioctl command can provide a timestamp of the last disc change known to them and receive an indication whether the disc was changed since then and the updated timestamp. I considered fixing the buggy behavior in the original CDROM_MEDIA_CHANGED ioctl but that would require maintaining state for each calling process in the kernel, which seems like a worse solution than introducing this new ioctl. Signed-off-by: Lukas Prediger <lumip@xxxxxxxx> Link: https://lore.kernel.org/all/20210912191207.74449-1-lumip@xxxxxxxx Signed-off-by: Phillip Potter <phil@xxxxxxxxxxxxxxxx> --- Documentation/cdrom/cdrom-standard.rst | 11 ++++ Documentation/userspace-api/ioctl/cdrom.rst | 3 ++ drivers/cdrom/cdrom.c | 59 +++++++++++++++++++-- include/linux/cdrom.h | 1 + include/uapi/linux/cdrom.h | 19 +++++++ 5 files changed, 89 insertions(+), 4 deletions(-) diff --git a/Documentation/cdrom/cdrom-standard.rst b/Documentation/cdrom/cdrom-standard.rst index 5845960ca382..52ea7b6b2fe8 100644 --- a/Documentation/cdrom/cdrom-standard.rst +++ b/Documentation/cdrom/cdrom-standard.rst @@ -907,6 +907,17 @@ commands can be identified by the underscores in their names. specifies the slot for which the information is given. The special value *CDSL_CURRENT* requests that information about the currently selected slot be returned. +`CDROM_TIMED_MEDIA_CHANGE` + Checks whether the disc has been changed since a user supplied time + and returns the time of the last disc change. + + *arg* is a pointer to a *cdrom_timed_media_change_info* struct. + *arg->last_media_change* may be set by calling code to signal + the timestamp of the last known media change (by the caller). + Upon successful return, this ioctl call will set + *arg->last_media_change* to the latest media change timestamp (in ms) + known by the kernel/driver and set *arg->has_changed* to 1 if + that timestamp is more recent than the timestamp set by the caller. `CDROM_DRIVE_STATUS` Returns the status of the drive by a call to *drive_status()*. Return values are defined in cdrom_drive_status_. diff --git a/Documentation/userspace-api/ioctl/cdrom.rst b/Documentation/userspace-api/ioctl/cdrom.rst index 3b4c0506de46..bac5bbf93ca0 100644 --- a/Documentation/userspace-api/ioctl/cdrom.rst +++ b/Documentation/userspace-api/ioctl/cdrom.rst @@ -54,6 +54,9 @@ are as follows: CDROM_SELECT_SPEED Set the CD-ROM speed CDROM_SELECT_DISC Select disc (for juke-boxes) CDROM_MEDIA_CHANGED Check is media changed + CDROM_TIMED_MEDIA_CHANGE Check if media changed + since given time + (struct cdrom_timed_media_change_info) CDROM_DRIVE_STATUS Get tray position, etc. CDROM_DISC_STATUS Get disc type, etc. CDROM_CHANGER_NSLOTS Get number of slots diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c index bd2e5b1560f5..89a68457820a 100644 --- a/drivers/cdrom/cdrom.c +++ b/drivers/cdrom/cdrom.c @@ -344,6 +344,12 @@ static void cdrom_sysctl_register(void); static LIST_HEAD(cdrom_list); +static void signal_media_change(struct cdrom_device_info *cdi) +{ + cdi->mc_flags = 0x3; /* set media changed bits, on both queues */ + cdi->last_media_change_ms = ktime_to_ms(ktime_get()); +} + int cdrom_dummy_generic_packet(struct cdrom_device_info *cdi, struct packet_command *cgc) { @@ -616,6 +622,7 @@ int register_cdrom(struct gendisk *disk, struct cdrom_device_info *cdi) ENSURE(cdo, generic_packet, CDC_GENERIC_PACKET); cdi->mc_flags = 0; cdi->options = CDO_USE_FFLAGS; + cdi->last_media_change_ms = ktime_to_ms(ktime_get()); if (autoclose == 1 && CDROM_CAN(CDC_CLOSE_TRAY)) cdi->options |= (int) CDO_AUTO_CLOSE; @@ -1421,8 +1428,7 @@ static int cdrom_select_disc(struct cdrom_device_info *cdi, int slot) cdi->ops->check_events(cdi, 0, slot); if (slot == CDSL_NONE) { - /* set media changed bits, on both queues */ - cdi->mc_flags = 0x3; + signal_media_change(cdi); return cdrom_load_unload(cdi, -1); } @@ -1455,7 +1461,7 @@ static int cdrom_select_disc(struct cdrom_device_info *cdi, int slot) slot = curslot; /* set media changed bits on both queues */ - cdi->mc_flags = 0x3; + signal_media_change(cdi); if ((ret = cdrom_load_unload(cdi, slot))) return ret; @@ -1521,7 +1527,7 @@ int media_changed(struct cdrom_device_info *cdi, int queue) cdi->ioctl_events = 0; if (changed) { - cdi->mc_flags = 0x3; /* set bit on both queues */ + signal_media_change(cdi); ret |= 1; cdi->media_written = 0; } @@ -2336,6 +2342,49 @@ static int cdrom_ioctl_media_changed(struct cdrom_device_info *cdi, return ret; } +/* + * Media change detection with timing information. + * + * arg is a pointer to a cdrom_timed_media_change_info struct. + * arg->last_media_change may be set by calling code to signal + * the timestamp (in ms) of the last known media change (by the caller). + * Upon successful return, ioctl call will set arg->last_media_change + * to the latest media change timestamp known by the kernel/driver + * and set arg->has_changed to 1 if that timestamp is more recent + * than the timestamp set by the caller. + */ +static int cdrom_ioctl_timed_media_change(struct cdrom_device_info *cdi, + unsigned long arg) +{ + int ret; + struct cdrom_timed_media_change_info __user *info; + struct cdrom_timed_media_change_info tmp_info; + + if (!CDROM_CAN(CDC_MEDIA_CHANGED)) + return -ENOSYS; + + info = (struct cdrom_timed_media_change_info __user *)arg; + cd_dbg(CD_DO_IOCTL, "entering CDROM_TIMED_MEDIA_CHANGE\n"); + + ret = cdrom_ioctl_media_changed(cdi, CDSL_CURRENT); + if (ret < 0) + return ret; + + if (copy_from_user(&tmp_info, info, sizeof(tmp_info)) != 0) + return -EFAULT; + + tmp_info.media_flags = 0; + if (tmp_info.last_media_change - cdi->last_media_change_ms < 0) + tmp_info.media_flags |= MEDIA_CHANGED_FLAG; + + tmp_info.last_media_change = cdi->last_media_change_ms; + + if (copy_to_user(info, &tmp_info, sizeof(*info)) != 0) + return -EFAULT; + + return 0; +} + static int cdrom_ioctl_set_options(struct cdrom_device_info *cdi, unsigned long arg) { @@ -3313,6 +3362,8 @@ int cdrom_ioctl(struct cdrom_device_info *cdi, struct block_device *bdev, return cdrom_ioctl_eject_sw(cdi, arg); case CDROM_MEDIA_CHANGED: return cdrom_ioctl_media_changed(cdi, arg); + case CDROM_TIMED_MEDIA_CHANGE: + return cdrom_ioctl_timed_media_change(cdi, arg); case CDROM_SET_OPTIONS: return cdrom_ioctl_set_options(cdi, arg); case CDROM_CLEAR_OPTIONS: diff --git a/include/linux/cdrom.h b/include/linux/cdrom.h index c4fef00abdf3..0a89f111e00e 100644 --- a/include/linux/cdrom.h +++ b/include/linux/cdrom.h @@ -64,6 +64,7 @@ struct cdrom_device_info { int for_data; int (*exit)(struct cdrom_device_info *); int mrw_mode_page; + __s64 last_media_change_ms; }; struct cdrom_device_ops { diff --git a/include/uapi/linux/cdrom.h b/include/uapi/linux/cdrom.h index 6c34f6e2f1f7..804ff8d98f71 100644 --- a/include/uapi/linux/cdrom.h +++ b/include/uapi/linux/cdrom.h @@ -147,6 +147,8 @@ #define CDROM_NEXT_WRITABLE 0x5394 /* get next writable block */ #define CDROM_LAST_WRITTEN 0x5395 /* get last block written on disc */ +#define CDROM_TIMED_MEDIA_CHANGE 0x5396 /* get the timestamp of the last media change */ + /******************************************************* * CDROM IOCTL structures *******************************************************/ @@ -295,6 +297,23 @@ struct cdrom_generic_command }; }; +/* This struct is used by CDROM_TIMED_MEDIA_CHANGE */ +struct cdrom_timed_media_change_info { + __s64 last_media_change; /* Timestamp of the last detected media + * change in ms. May be set by caller, + * updated upon successful return of + * ioctl. + */ + __u64 media_flags; /* Flags returned by ioctl to indicate + * media status. + */ +}; +#define MEDIA_CHANGED_FLAG 0x1 /* Last detected media change was more + * recent than last_media_change set by + * caller. + */ +/* other bits of media_flags available for future use */ + /* * A CD-ROM physical sector size is 2048, 2052, 2056, 2324, 2332, 2336, * 2340, or 2352 bytes long. -- 2.31.1
