ext4: support read-only images
Add a rocompat feature, "readonly" to mark a FS image as read-only.
The feature prevents the kernel and e2fsprogs from changing the image;
the flag can be toggled by tune2fs.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 95b388c..60db5a1 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2776,6 +2776,12 @@
if (readonly)
return 1;
+ if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_READONLY)) {
+ ext4_msg(sb, KERN_INFO, "filesystem is read-only");
+ sb->s_flags |= MS_RDONLY;
+ return 1;
+ }
+
/* Check that feature set is OK for a read-write mount */
if (EXT4_HAS_RO_COMPAT_FEATURE(sb, ~EXT4_FEATURE_RO_COMPAT_SUPP)) {
ext4_msg(sb, KERN_ERR, "couldn't mount RDWR because of "
@@ -4929,7 +4935,9 @@
ext4_mark_recovery_complete(sb, es);
} else {
/* Make sure we can mount this feature set readwrite */
- if (!ext4_feature_set_ok(sb, 0)) {
+ if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
+ EXT4_FEATURE_RO_COMPAT_READONLY) ||
+ !ext4_feature_set_ok(sb, 0)) {
err = -EROFS;
goto restore_opts;
}