2.6.38-stable review patch.  If anyone has any objections, please let us know.

------------------
 devices

From: Tejun Heo <[email protected]>

commit d4dc210f69bcb0b4bef5a83b1c323817be89bad1 upstream.

Disk event code automatically blocks events on excl write.  This is
primarily to avoid issuing polling commands while burning is in
progress.  This behavior doesn't fit other types of devices with
removeable media where polling commands don't have adverse side
effects and door locking usually doesn't exist.

This patch introduces new genhd flag which controls the auto-blocking
behavior and uses it to enable auto-blocking only on optical devices.

Note for stable: 2.6.38 and later only

Signed-off-by: Tejun Heo <[email protected]>
Reported-by: Kay Sievers <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

---
 drivers/block/paride/pcd.c |    1 +
 drivers/cdrom/viocd.c      |    3 ++-
 drivers/ide/ide-cd.c       |    2 +-
 drivers/scsi/sr.c          |    2 +-
 fs/block_dev.c             |   17 ++++++++++-------
 include/linux/genhd.h      |    1 +
 6 files changed, 16 insertions(+), 10 deletions(-)

--- a/drivers/block/paride/pcd.c
+++ b/drivers/block/paride/pcd.c
@@ -320,6 +320,7 @@ static void pcd_init_units(void)
                disk->first_minor = unit;
                strcpy(disk->disk_name, cd->name);      /* umm... */
                disk->fops = &pcd_bdops;
+               disk->flags = GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE;
                disk->events = DISK_EVENT_MEDIA_CHANGE;
        }
 }
--- a/drivers/cdrom/viocd.c
+++ b/drivers/cdrom/viocd.c
@@ -625,7 +625,8 @@ static int viocd_probe(struct vio_dev *v
        blk_queue_max_hw_sectors(q, 4096 / 512);
        gendisk->queue = q;
        gendisk->fops = &viocd_fops;
-       gendisk->flags = GENHD_FL_CD|GENHD_FL_REMOVABLE;
+       gendisk->flags = GENHD_FL_CD | GENHD_FL_REMOVABLE |
+                        GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE;
        gendisk->events = DISK_EVENT_MEDIA_CHANGE;
        set_capacity(gendisk, 0);
        gendisk->private_data = d;
--- a/drivers/ide/ide-cd.c
+++ b/drivers/ide/ide-cd.c
@@ -1790,7 +1790,7 @@ static int ide_cd_probe(ide_drive_t *dri
 
        ide_cd_read_toc(drive, &sense);
        g->fops = &idecd_ops;
-       g->flags |= GENHD_FL_REMOVABLE;
+       g->flags |= GENHD_FL_REMOVABLE | GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE;
        g->events = DISK_EVENT_MEDIA_CHANGE;
        add_disk(g);
        return 0;
--- a/drivers/scsi/sr.c
+++ b/drivers/scsi/sr.c
@@ -636,7 +636,7 @@ static int sr_probe(struct device *dev)
        disk->first_minor = minor;
        sprintf(disk->disk_name, "sr%d", minor);
        disk->fops = &sr_bdops;
-       disk->flags = GENHD_FL_CD;
+       disk->flags = GENHD_FL_CD | GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE;
        disk->events = DISK_EVENT_MEDIA_CHANGE | DISK_EVENT_EJECT_REQUEST;
 
        blk_queue_rq_timeout(sdev->request_queue, SR_TIMEOUT);
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1233,6 +1233,8 @@ int blkdev_get(struct block_device *bdev
        res = __blkdev_get(bdev, mode, 0);
 
        if (whole) {
+               struct gendisk *disk = whole->bd_disk;
+
                /* finish claiming */
                mutex_lock(&bdev->bd_mutex);
                spin_lock(&bdev_lock);
@@ -1259,15 +1261,16 @@ int blkdev_get(struct block_device *bdev
                spin_unlock(&bdev_lock);
 
                /*
-                * Block event polling for write claims.  Any write
-                * holder makes the write_holder state stick until all
-                * are released.  This is good enough and tracking
-                * individual writeable reference is too fragile given
-                * the way @mode is used in blkdev_get/put().
+                * Block event polling for write claims if requested.  Any
+                * write holder makes the write_holder state stick until
+                * all are released.  This is good enough and tracking
+                * individual writeable reference is too fragile given the
+                * way @mode is used in blkdev_get/put().
                 */
-               if (!res && (mode & FMODE_WRITE) && !bdev->bd_write_holder) {
+               if ((disk->flags & GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE) &&
+                   !res && (mode & FMODE_WRITE) && !bdev->bd_write_holder) {
                        bdev->bd_write_holder = true;
-                       disk_block_events(bdev->bd_disk);
+                       disk_block_events(disk);
                }
 
                mutex_unlock(&bdev->bd_mutex);
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -127,6 +127,7 @@ struct hd_struct {
 #define GENHD_FL_SUPPRESS_PARTITION_INFO       32
 #define GENHD_FL_EXT_DEVT                      64 /* allow extended devt */
 #define GENHD_FL_NATIVE_CAPACITY               128
+#define GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE    256
 
 enum {
        DISK_EVENT_MEDIA_CHANGE                 = 1 << 0, /* media changed */


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