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authorDarrick J. Wong <darrick.wong@oracle.com>2015-02-12 22:31:21 -0500
committerTheodore Ts'o <tytso@mit.edu>2015-02-12 22:31:21 -0500
commit2cb5cc8b09c939c77826635956c35995b15c9331 (patch)
treea172f96f3dca8c8432786eef7d103138ef859370
parent04ecddb73dd83d1094a904b8d03c57880998daee (diff)
downloadop-kernel-dev-2cb5cc8b09c939c77826635956c35995b15c9331.zip
op-kernel-dev-2cb5cc8b09c939c77826635956c35995b15c9331.tar.gz
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>
-rw-r--r--fs/ext4/ext4.h1
-rw-r--r--fs/ext4/super.c10
2 files changed, 10 insertions, 1 deletions
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index b7f393d..7fec2ef 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1530,6 +1530,7 @@ 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 95b388c..60db5a1 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 "
@@ -4929,7 +4935,9 @@ 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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