target/iblock: Add parameter to specify read-only devices

see https://bugzilla.redhat.com/show_bug.cgi?id=818855

Adds a parameter so read-only block devices may be registered as
LIO backstores.

Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

2 files changed, 29 insertions, 7 deletions

diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c
index 244fff4aaf5a..c2d4ccbb7133 100644
--- a/drivers/target/target_core_iblock.c
+++ b/drivers/target/target_core_iblock.c
@@ -96,6 +96,7 @@ static struct se_device *iblock_create_virtdevice(
         struct request_queue *q;
         struct queue_limits *limits;
         u32 dev_flags = 0;
+        fmode_t mode;
         int ret = -EINVAL;
 
         if (!ib_dev) {
@@ -117,8 +118,11 @@ static struct se_device *iblock_create_virtdevice(
         pr_debug( "IBLOCK: Claiming struct block_device: %s\n",
                         ib_dev->ibd_udev_path);
 
-        bd = blkdev_get_by_path(ib_dev->ibd_udev_path,
-                                FMODE_WRITE|FMODE_READ|FMODE_EXCL, ib_dev);
+        mode = FMODE_READ|FMODE_EXCL;
+        if (!ib_dev->ibd_readonly)
+                mode |= FMODE_WRITE;
+
+        bd = blkdev_get_by_path(ib_dev->ibd_udev_path, mode, ib_dev);
         if (IS_ERR(bd)) {
                 ret = PTR_ERR(bd);
                 goto failed;
@@ -323,11 +327,12 @@ static int iblock_do_discard(struct se_device *dev, sector_t lba, u32 range)
 }
 
 enum {
-        Opt_udev_path, Opt_force, Opt_err
+        Opt_udev_path, Opt_readonly, Opt_force, Opt_err
 };
 
 static match_table_t tokens = {
         {Opt_udev_path, "udev_path=%s"},
+        {Opt_readonly, "readonly=%d"},
         {Opt_force, "force=%d"},
         {Opt_err, NULL}
 };
@@ -340,6 +345,7 @@ static ssize_t iblock_set_configfs_dev_params(struct se_hba *hba,
         char *orig, *ptr, *arg_p, *opts;
         substring_t args[MAX_OPT_ARGS];
         int ret = 0, token;
+        unsigned long tmp_readonly;
 
         opts = kstrdup(page, GFP_KERNEL);
         if (!opts)
@@ -372,6 +378,22 @@ static ssize_t iblock_set_configfs_dev_params(struct se_hba *hba,
                                         ib_dev->ibd_udev_path);
                         ib_dev->ibd_flags |= IBDF_HAS_UDEV_PATH;
                         break;
+                case Opt_readonly:
+                        arg_p = match_strdup(&args[0]);
+                        if (!arg_p) {
+                                ret = -ENOMEM;
+                                break;
+                        }
+                        ret = strict_strtoul(arg_p, 0, &tmp_readonly);
+                        kfree(arg_p);
+                        if (ret < 0) {
+                                pr_err("strict_strtoul() failed for"
+                                                " readonly=\n");
+                                goto out;
+                        }
+                        ib_dev->ibd_readonly = tmp_readonly;
+                        pr_debug("IBLOCK: readonly: %d\n", ib_dev->ibd_readonly);
+                        break;
                 case Opt_force:
                         break;
                 default:
@@ -411,11 +433,10 @@ static ssize_t iblock_show_configfs_dev_params(
         if (bd)
                 bl += sprintf(b + bl, "iBlock device: %s",
                                 bdevname(bd, buf));
-        if (ibd->ibd_flags & IBDF_HAS_UDEV_PATH) {
-                bl += sprintf(b + bl, "  UDEV PATH: %s\n",
+        if (ibd->ibd_flags & IBDF_HAS_UDEV_PATH)
+                bl += sprintf(b + bl, "  UDEV PATH: %s",
                                 ibd->ibd_udev_path);
-        } else
-                bl += sprintf(b + bl, "\n");
+        bl += sprintf(b + bl, "  readonly: %d\n", ibd->ibd_readonly);
 
         bl += sprintf(b + bl, "        ");
         if (bd) {
diff --git a/drivers/target/target_core_iblock.h b/drivers/target/target_core_iblock.h
index 66cf7b9e205e..533627ae79ec 100644
--- a/drivers/target/target_core_iblock.h
+++ b/drivers/target/target_core_iblock.h
@@ -18,6 +18,7 @@ struct iblock_dev {
         u32     ibd_flags;
         struct bio_set  *ibd_bio_set;
         struct block_device *ibd_bd;
+        bool ibd_readonly;
 } ____cacheline_aligned;
 
 #endif /* TARGET_CORE_IBLOCK_H */