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) we probably want the ext4 driver
to load, not ext2.
Reported-by: Dave Chinner <david@xxxxxxxxxxxxx>
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
fs/ext2/ext2.h | 6 +++++-
fs/ext2/super.c | 13 ++++++++++---
2 files changed, 15 insertions(+), 4 deletions(-)
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..4efb018 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -896,6 +896,16 @@ 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 */
+ features = EXT2_HAS_COMPAT_FEATURE(sb, ~EXT2_FEATURE_COMPAT_SUPP);
+ if (features) {
+ ext2_msg(sb, KERN_ERR, "error: won't mount because of "
+ "unsupported optional features (%x); try ext4",
+ le32_to_cpu(features));
+ goto failed_mount;
+ }
+#endif
features = EXT2_HAS_INCOMPAT_FEATURE(sb, ~EXT2_FEATURE_INCOMPAT_SUPP);
if (features) {
ext2_msg(sb, KERN_ERR, "error: couldn't mount because of "
--
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