dm thin: open dev read only when possible
If a thin pool is created in read-only-metadata mode then only open the
metadata device read-only.
Previously it was always opened with FMODE_READ | FMODE_WRITE.
(Note that dm_get_device() still allows read-only dm devices to be used
read-write at the moment: If I create a read-only linear device for the
metadata, via dmsetup load --readonly, then I can still create a rw pool
out of it.)
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 111c148..ef021b0 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -1945,6 +1945,7 @@
unsigned long block_size;
dm_block_t low_water_blocks;
struct dm_dev *metadata_dev;
+ fmode_t metadata_mode;
/*
* FIXME Remove validation from scope of lock.
@@ -1956,10 +1957,22 @@
r = -EINVAL;
goto out_unlock;
}
+
as.argc = argc;
as.argv = argv;
- r = dm_get_device(ti, argv[0], FMODE_READ | FMODE_WRITE, &metadata_dev);
+ /*
+ * Set default pool features.
+ */
+ pool_features_init(&pf);
+
+ dm_consume_args(&as, 4);
+ r = parse_pool_features(&as, &pf, ti);
+ if (r)
+ goto out_unlock;
+
+ metadata_mode = FMODE_READ | ((pf.mode == PM_READ_ONLY) ? 0 : FMODE_WRITE);
+ r = dm_get_device(ti, argv[0], metadata_mode, &metadata_dev);
if (r) {
ti->error = "Error opening metadata block device";
goto out_unlock;
@@ -1992,16 +2005,6 @@
goto out;
}
- /*
- * Set default pool features.
- */
- pool_features_init(&pf);
-
- dm_consume_args(&as, 4);
- r = parse_pool_features(&as, &pf, ti);
- if (r)
- goto out;
-
pt = kzalloc(sizeof(*pt), GFP_KERNEL);
if (!pt) {
r = -ENOMEM;