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@xxxxxxxxxx>
---
fs/ext4/ext4.h | 1 +
fs/ext4/super.c | 10 +++++++++-
2 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 3950a2f..5cf937d 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1557,6 +1557,7 @@ static inline void ext4_clear_state_flags(struct ext4_inode_info *ei)
* GDT_CSUM bits are mutually exclusive.
*/
#define EXT4_FEATURE_RO_COMPAT_METADATA_CSUM 0x0400
+#define EXT4_FEATURE_RO_COMPAT_READONLY 0x1000
#define EXT4_FEATURE_INCOMPAT_COMPRESSION 0x0001
#define EXT4_FEATURE_INCOMPAT_FILETYPE 0x0002
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 74c5f53..c65dede 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2776,6 +2776,12 @@ static int ext4_feature_set_ok(struct super_block *sb, int readonly)
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 "
@@ -4930,7 +4936,9 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
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;
}
--
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