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>

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>
Joe Thornber · Alasdair G Kergon
1 parent b17446df2e
Showing 1 changed file with 14 additions and 11 deletions Side-by-side Diff
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;
@@ -1991,16 +2004,6 @@
 		r = -EINVAL;
 		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) {
...	...	@@ -1945,6 +1945,7 @@
1945	1945	unsigned long block_size;
1946	1946	dm_block_t low_water_blocks;
1947	1947	struct dm_dev *metadata_dev;
	1948	+ fmode_t metadata_mode;
1948	1949
1949	1950	/*
1950	1951	* FIXME Remove validation from scope of lock.
1951	1952
...	...	@@ -1956,10 +1957,22 @@
1956	1957	r = -EINVAL;
1957	1958	goto out_unlock;
1958	1959	}
	1960	+
1959	1961	as.argc = argc;
1960	1962	as.argv = argv;
1961	1963
1962		- r = dm_get_device(ti, argv[0], FMODE_READ \| FMODE_WRITE, &metadata_dev);
	1964	+ /*
	1965	+ * Set default pool features.
	1966	+ */
	1967	+ pool_features_init(&pf);
	1968	+
	1969	+ dm_consume_args(&as, 4);
	1970	+ r = parse_pool_features(&as, &pf, ti);
	1971	+ if (r)
	1972	+ goto out_unlock;
	1973	+
	1974	+ metadata_mode = FMODE_READ \| ((pf.mode == PM_READ_ONLY) ? 0 : FMODE_WRITE);
	1975	+ r = dm_get_device(ti, argv[0], metadata_mode, &metadata_dev);
1963	1976	if (r) {
1964	1977	ti->error = "Error opening metadata block device";
1965	1978	goto out_unlock;
...	...	@@ -1991,16 +2004,6 @@
1991	2004	r = -EINVAL;
1992	2005	goto out;
1993	2006	}
1994		-
1995		- /*
1996		- * Set default pool features.
1997		- */
1998		- pool_features_init(&pf);
1999		-
2000		- dm_consume_args(&as, 4);
2001		- r = parse_pool_features(&as, &pf, ti);
2002		- if (r)
2003		- goto out;
2004	2007
2005	2008	pt = kzalloc(sizeof(*pt), GFP_KERNEL);
2006	2009	if (!pt) {