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authorLukas Prediger <lumip@lumip.de>2021-09-14 02:09:42 +0300
committerJens Axboe <axboe@kernel.dk>2021-09-15 05:05:26 +0300
commit67f1e027c27054e641584655020a417eaac9cb3a (patch)
treecd436e8c697009cc6def17e4b77cd28503029ac3
parent316346243be6df12799c0b64b788e06bad97c30b (diff)
downloadlinux-67f1e027c27054e641584655020a417eaac9cb3a.tar.xz
drivers/cdrom: improved ioctl for media change detection
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@lumip.de> Link: https://lore.kernel.org/all/20210912191207.74449-1-lumip@lumip.de Signed-off-by: Phillip Potter <phil@philpotter.co.uk> Link: https://lore.kernel.org/r/20210913230942.1188-1-phil@philpotter.co.uk Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--Documentation/cdrom/cdrom-standard.rst11
-rw-r--r--Documentation/userspace-api/ioctl/cdrom.rst3
-rw-r--r--drivers/cdrom/cdrom.c59
-rw-r--r--include/linux/cdrom.h1
-rw-r--r--include/uapi/linux/cdrom.h19
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.