1 files changed, 40 insertions, 4 deletions

diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
index 16ab8d363ac6..6bc27d52326f 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -35,14 +35,17 @@
 static int dcssblk_open(struct inode *inode, struct file *filp);
 static int dcssblk_release(struct inode *inode, struct file *filp);
 static int dcssblk_make_request(struct request_queue *q, struct bio *bio);
+static int dcssblk_direct_access(struct block_device *bdev, sector_t secnum,
+                                 unsigned long *data);
 
 static char dcssblk_segments[DCSSBLK_PARM_LEN] = "\0";
 
 static int dcssblk_major;
 static struct block_device_operations dcssblk_devops = {
-        .owner   = THIS_MODULE,
-        .open    = dcssblk_open,
-        .release = dcssblk_release,
+        .owner          = THIS_MODULE,
+        .open           = dcssblk_open,
+        .release        = dcssblk_release,
+        .direct_access  = dcssblk_direct_access,
 };
 
 static ssize_t dcssblk_add_store(struct device * dev, struct device_attribute *attr, const char * buf,
@@ -641,6 +644,20 @@ dcssblk_make_request(request_queue_t *q, struct bio *bio)
                 /* Request beyond end of DCSS segment. */
                 goto fail;
         }
+        /* verify data transfer direction */
+        if (dev_info->is_shared) {
+                switch (dev_info->segment_type) {
+                case SEG_TYPE_SR:
+                case SEG_TYPE_ER:
+                case SEG_TYPE_SC:
+                        /* cannot write to these segments */
+                        if (bio_data_dir(bio) == WRITE) {
+                                PRINT_WARN("rejecting write to ro segment %s\n", dev_info->dev.bus_id);
+                                goto fail;
+                        }
+                }
+        }
+
         index = (bio->bi_sector >> 3);
         bio_for_each_segment(bvec, bio, i) {
                 page_addr = (unsigned long)
@@ -661,7 +678,26 @@ dcssblk_make_request(request_queue_t *q, struct bio *bio)
         bio_endio(bio, bytes_done, 0);
         return 0;
 fail:
-        bio_io_error(bio, bytes_done);
+        bio_io_error(bio, bio->bi_size);
+        return 0;
+}
+
+static int
+dcssblk_direct_access (struct block_device *bdev, sector_t secnum,
+                        unsigned long *data)
+{
+        struct dcssblk_dev_info *dev_info;
+        unsigned long pgoff;
+
+        dev_info = bdev->bd_disk->private_data;
+        if (!dev_info)
+                return -ENODEV;
+        if (secnum % (PAGE_SIZE/512))
+                return -EINVAL;
+        pgoff = secnum / (PAGE_SIZE / 512);
+        if ((pgoff+1)*PAGE_SIZE-1 > dev_info->end - dev_info->start)
+                return -ERANGE;
+        *data = (unsigned long) (dev_info->start+pgoff*PAGE_SIZE);
         return 0;
 }