[PATCH] dm: create error table

Add a library function dm_create_error_table() to create a table that rejects
any I/O sent to a device with EIO.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 10c9439..827b648 100644 (file)
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -237,6 +237,44 @@ int dm_table_create(struct dm_table **result, int mode,
        return 0;
 }
 
+int dm_create_error_table(struct dm_table **result, struct mapped_device *md)
+{
+       struct dm_table *t;
+       sector_t dev_size = 1;
+       int r;
+
+       /*
+        * Find current size of device.
+        * Default to 1 sector if inactive.
+        */
+       t = dm_get_table(md);
+       if (t) {
+               dev_size = dm_table_get_size(t);
+               dm_table_put(t);
+       }
+
+       r = dm_table_create(&t, FMODE_READ, 1, md);
+       if (r)
+               return r;
+
+       r = dm_table_add_target(t, "error", 0, dev_size, NULL);
+       if (r)
+               goto out;
+
+       r = dm_table_complete(t);
+       if (r)
+               goto out;
+
+       *result = t;
+
+out:
+       if (r)
+               dm_table_put(t);
+
+       return r;
+}
+EXPORT_SYMBOL_GPL(dm_create_error_table);
+
 static void free_devices(struct list_head *devices)
 {
        struct list_head *tmp, *next;

diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 010c8c5..61103d2 100644 (file)
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -227,5 +227,11 @@ void dm_table_event(struct dm_table *t);
  */
 int dm_swap_table(struct mapped_device *md, struct dm_table *t);
 
+/*
+ * Prepare a table for a device that will error all I/O.
+ * To make it active, call dm_suspend(), dm_swap_table() then dm_resume().
+ */
+int dm_create_error_table(struct dm_table **result, struct mapped_device *md);
+
 #endif /* __KERNEL__ */
 #endif /* _LINUX_DEVICE_MAPPER_H */