[SCSI] sd: implement sd_check_events()

Replace sd_media_change() with sd_check_events().

* Move media removed logic into set_media_not_present() and
  media_not_present() and set sdev->changed iff an existing media is
  removed or the device indicates UNIT_ATTENTION.

* Make sd_check_events() sets sdev->changed if previously missing
  media becomes present.

* Event is reported only if sdev->changed is set.

This makes media presence event reported if scsi_disk->media_present
actually changed or the device indicated UNIT_ATTENTION.  For backward
compatibility, SDEV_EVT_MEDIA_CHANGE is generated each time
sd_check_events() detects media change event.

[jejb: fix boot failure]
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

2 files changed, 53 insertions, 52 deletions

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index b65e65aa07eb..7d257465bd98 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -990,30 +990,51 @@ out:
 
 static void set_media_not_present(struct scsi_disk *sdkp)
 {
-        sdkp->media_present = 0;
-        sdkp->capacity = 0;
-        sdkp->device->changed = 1;
+        if (sdkp->media_present)
+                sdkp->device->changed = 1;
+
+        if (sdkp->device->removable) {
+                sdkp->media_present = 0;
+                sdkp->capacity = 0;
+        }
+}
+
+static int media_not_present(struct scsi_disk *sdkp,
+                             struct scsi_sense_hdr *sshdr)
+{
+        if (!scsi_sense_valid(sshdr))
+                return 0;
+
+        /* not invoked for commands that could return deferred errors */
+        switch (sshdr->sense_key) {
+        case UNIT_ATTENTION:
+        case NOT_READY:
+                /* medium not present */
+                if (sshdr->asc == 0x3A) {
+                        set_media_not_present(sdkp);
+                        return 1;
+                }
+        }
+        return 0;
 }
 
 /**
- *      sd_media_changed - check if our medium changed
- *      @disk: kernel device descriptor 
+ *      sd_check_events - check media events
+ *      @disk: kernel device descriptor
+ *      @clearing: disk events currently being cleared
  *
- *      Returns 0 if not applicable or no change; 1 if change
+ *      Returns mask of DISK_EVENT_*.
  *
  *      Note: this function is invoked from the block subsystem.
  **/
-static int sd_media_changed(struct gendisk *disk)
+static unsigned int sd_check_events(struct gendisk *disk, unsigned int clearing)
 {
         struct scsi_disk *sdkp = scsi_disk(disk);
         struct scsi_device *sdp = sdkp->device;
         struct scsi_sense_hdr *sshdr = NULL;
         int retval;
 
-        SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp, "sd_media_changed\n"));
-
-        if (!sdp->removable)
-                return 0;
+        SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp, "sd_check_events\n"));
 
         /*
          * If the device is offline, don't send any commands - just pretend as
@@ -1043,40 +1064,37 @@ static int sd_media_changed(struct gendisk *disk)
                                               sshdr);
         }
 
-        if (retval) {
+        /* failed to execute TUR, assume media not present */
+        if (host_byte(retval)) {
                 set_media_not_present(sdkp);
                 goto out;
         }
 
+        if (media_not_present(sdkp, sshdr))
+                goto out;
+
         /*
          * For removable scsi disk we have to recognise the presence
-         * of a disk in the drive. This is kept in the struct scsi_disk
-         * struct and tested at open !  Daniel Roche (dan@lectra.fr)
+         * of a disk in the drive.
          */
+        if (!sdkp->media_present)
+                sdp->changed = 1;
         sdkp->media_present = 1;
-
 out:
         /*
-         * Report a media change under the following conditions:
+         * sdp->changed is set under the following conditions:
          *
-         *      Medium is present now and wasn't present before.
-         *      Medium wasn't present before and is present now.
-         *      Medium was present at all times, but it changed while
-         *              we weren't looking (sdp->changed is set).
+         *      Medium present state has changed in either direction.
+         *      Device has indicated UNIT_ATTENTION.
          *
-         * If there was no medium before and there is no medium now then
-         * don't report a change, even if a medium was inserted and removed
-         * while we weren't looking.
+         * Report SDEV_EVT_MEDIA_CHANGE too for backward compatibility.
          */
-        retval = (sdkp->media_present != sdkp->previous_state ||
-                        (sdkp->media_present && sdp->changed));
-        if (retval)
+        if (sdp->changed)
                 sdev_evt_send_simple(sdp, SDEV_EVT_MEDIA_CHANGE, GFP_KERNEL);
-        sdkp->previous_state = sdkp->media_present;
-
-        /* sdp->changed indicates medium was changed or is not present */
-        sdp->changed = !sdkp->media_present;
         kfree(sshdr);
+
+        retval = sdp->changed ? DISK_EVENT_MEDIA_CHANGE : 0;
+        sdp->changed = 0;
         return retval;
 }
 
@@ -1169,7 +1187,7 @@ static const struct block_device_operations sd_fops = {
 #ifdef CONFIG_COMPAT
         .compat_ioctl           = sd_compat_ioctl,
 #endif
-        .media_changed          = sd_media_changed,
+        .check_events           = sd_check_events,
         .revalidate_disk        = sd_revalidate_disk,
         .unlock_native_capacity = sd_unlock_native_capacity,
 };
@@ -1312,23 +1330,6 @@ static int sd_done(struct scsi_cmnd *SCpnt)
         return good_bytes;
 }
 
-static int media_not_present(struct scsi_disk *sdkp,
-                             struct scsi_sense_hdr *sshdr)
-{
-
-        if (!scsi_sense_valid(sshdr))
-                return 0;
-        /* not invoked for commands that could return deferred errors */
-        if (sshdr->sense_key != NOT_READY &&
-            sshdr->sense_key != UNIT_ATTENTION)
-                return 0;
-        if (sshdr->asc != 0x3A) /* medium not present */
-                return 0;
-
-        set_media_not_present(sdkp);
-        return 1;
-}
-
 /*
  * spinup disk - called only in sd_revalidate_disk()
  */
@@ -1503,7 +1504,7 @@ static void read_capacity_error(struct scsi_disk *sdkp, struct scsi_device *sdp,
          */
         if (sdp->removable &&
             sense_valid && sshdr->sense_key == NOT_READY)
-                sdp->changed = 1;
+                set_media_not_present(sdkp);
 
         /*
          * We used to set media_present to 0 here to indicate no media
@@ -2389,8 +2390,10 @@ static void sd_probe_async(void *data, async_cookie_t cookie)
 
         gd->driverfs_dev = &sdp->sdev_gendev;
         gd->flags = GENHD_FL_EXT_DEVT;
-        if (sdp->removable)
+        if (sdp->removable) {
                 gd->flags |= GENHD_FL_REMOVABLE;
+                gd->events |= DISK_EVENT_MEDIA_CHANGE;
+        }
 
         add_disk(gd);
         sd_dif_config_host(sdkp);
@@ -2472,7 +2475,6 @@ static int sd_probe(struct device *dev)
         sdkp->disk = gd;
         sdkp->index = index;
         atomic_set(&sdkp->openers, 0);
-        sdkp->previous_state = 1;
 
         if (!sdp->request_queue->rq_timeout) {
                 if (sdp->type != TYPE_MOD)
diff --git a/drivers/scsi/sd.h b/drivers/scsi/sd.h
index 55488faf0815..c9d8f6ca49e2 100644
--- a/drivers/scsi/sd.h
+++ b/drivers/scsi/sd.h
@@ -55,7 +55,6 @@ struct scsi_disk {
         u8              media_present;
         u8              write_prot;
         u8              protection_type;/* Data Integrity Field */
-        unsigned        previous_state : 1;
         unsigned        ATO : 1;        /* state of disk ATO bit */
         unsigned        WCE : 1;        /* state of disk WCE bit */
         unsigned        RCD : 1;        /* state of disk RCD bit, unused */