ext4: Add new "development flag" to the ext4 filesystem

This flag is simply a generic "this is a crash/burn test filesystem"
marker.  If it is set, then filesystem code which is "in development"
will be allowed to mount the filesystem.  Filesystem code which is not
considered ready for prime-time will check for this flag, and if it is
not set, it will refuse to touch the filesystem.

As we start rolling ext4 out to distro's like Fedora, et. al, this makes
it less likely that a user might accidentally start using ext4 on a
production filesystem; a bad thing, since that will essentially make it
be unfsckable until e2fsprogs catches up.

Signed-off-by: Theodore Tso <tytso@MIT.EDU>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 93beb865c20d30f129bac6fb1ed0d99fb699a485..0072da75221fe0c5ff933943b9ceb5170dcd347f 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1919,6 +1919,17 @@ static int ext4_fill_super (struct super_block *sb, void *data, int silent)
                printk(KERN_WARNING
                       "EXT4-fs warning: feature flags set on rev 0 fs, "
                       "running e2fsck is recommended\n");
+
+       /*
+        * Since ext4 is still considered development code, we require
+        * that the TEST_FILESYS flag in s->flags be set.
+        */
+       if (!(le32_to_cpu(es->s_flags) & EXT2_FLAGS_TEST_FILESYS)) {
+               printk(KERN_WARNING "EXT4-fs: %s: not marked "
+                      "OK to use with test code.\n", sb->s_id);
+               goto failed_mount;
+       }
+
        /*
         * Check feature flags regardless of the revision level, since we
         * previously didn't change the revision level when setting the flags,

diff --git a/include/linux/ext4_fs.h b/include/linux/ext4_fs.h
index c4f635a4dd254ff3ce0a79a976dd3a960925bc81..25003254859773c657f510d0e2460c900d47a6c9 100644 (file)
--- a/include/linux/ext4_fs.h
+++ b/include/linux/ext4_fs.h
@@ -489,6 +489,13 @@ do {                                                                              \
 #define        EXT4_ERROR_FS                   0x0002  /* Errors detected */
 #define        EXT4_ORPHAN_FS                  0x0004  /* Orphans being recovered */
 
+/*
+ * Misc. filesystem flags
+ */
+#define EXT2_FLAGS_SIGNED_HASH         0x0001  /* Signed dirhash in use */
+#define EXT2_FLAGS_UNSIGNED_HASH       0x0002  /* Unsigned dirhash in use */
+#define EXT2_FLAGS_TEST_FILESYS                0x0004  /* to test development code */
+
 /*
  * Mount flags
  */