The ext2 mount code never checks the compat features against the ones
it knows about. This is correct behavior since compat features are
supposed to be rw-compatible with old drivers; however, for certain
configurations (journalled rootfs) the admin is unlikely to want
no-journal mode. Since we changed the default probe order to put ext4
first, we can make ext2.ko only allow readonly mounts if has_journal is
found.
(Remember, this only affects mounting ext3 filesystems on ext2.ko.)
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
fs/ext2/ext2.h | 6 +++++-
fs/ext2/super.c | 19 +++++++++++++++++++
2 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/fs/ext2/ext2.h b/fs/ext2/ext2.h
index 8d15feb..ce508b1 100644
--- a/fs/ext2/ext2.h
+++ b/fs/ext2/ext2.h
@@ -547,7 +547,11 @@ struct ext2_super_block {
#define EXT2_FEATURE_INCOMPAT_META_BG 0x0010
#define EXT2_FEATURE_INCOMPAT_ANY 0xffffffff
-#define EXT2_FEATURE_COMPAT_SUPP EXT2_FEATURE_COMPAT_EXT_ATTR
+#define EXT2_FEATURE_COMPAT_SUPP (EXT2_FEATURE_COMPAT_DIR_PREALLOC| \
+ EXT2_FEATURE_COMPAT_IMAGIC_INODES| \
+ EXT2_FEATURE_COMPAT_EXT_ATTR| \
+ EXT2_FEATURE_COMPAT_RESIZE_INO| \
+ EXT2_FEATURE_COMPAT_DIR_INDEX)
#define EXT2_FEATURE_INCOMPAT_SUPP (EXT2_FEATURE_INCOMPAT_FILETYPE| \
EXT2_FEATURE_INCOMPAT_META_BG)
#define EXT2_FEATURE_RO_COMPAT_SUPP (EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER| \
diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 900e19c..40c312f 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -896,6 +896,14 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
* previously didn't change the revision level when setting the flags,
* so there is a chance incompat flags are set on a rev 0 filesystem.
*/
+#ifdef CONFIG_EXT4_FS
+ /* Journalled FS should mount with ext4 if it's available */
+ if (EXT2_HAS_COMPAT_FEATURE(sb, EXT3_FEATURE_COMPAT_HAS_JOURNAL)) {
+ ext2_msg(sb, KERN_ERR, "warning: journal detected; cowardly "
+ "refusing to mount read-write. Try ext4.");
+ sb->s_flags |= MS_RDONLY;
+ }
+#endif
features = EXT2_HAS_INCOMPAT_FEATURE(sb, ~EXT2_FEATURE_INCOMPAT_SUPP);
if (features) {
ext2_msg(sb, KERN_ERR, "error: couldn't mount because of "
@@ -1336,6 +1344,17 @@ static int ext2_remount (struct super_block * sb, int * flags, char * data)
err = -EROFS;
goto restore_opts;
}
+#ifdef CONFIG_EXT4_FS
+ /* Journalled FS should mount with ext4 if it's available */
+ if (EXT2_HAS_COMPAT_FEATURE(sb,
+ EXT3_FEATURE_COMPAT_HAS_JOURNAL)) {
+ ext2_msg(sb, KERN_ERR, "warning: journal detected; "
+ "cowardly refusing to remount read-write. "
+ "Try ext4.");
+ err = -EROFS;
+ goto restore_opts;
+ }
+#endif
/*
* Mounting a RDONLY partition read-write, so reread and
* store the current valid flag. (It may have been changed
--
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