ext4: do not set extents feature from the kernel
We've talked for a while about getting rid of any feature-
setting from the kernel; this gets rid of the code which would
set the INCOMPAT_EXTENTS flag on the first file write when mounted
as ext4[dev].
With this patch, if the extents feature is not already set on disk,
then mounting as ext4 will fall back to noextents with a warning,
and if -o extents is explicitly requested, the mount will fail,
also with warning.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 2bf9cdd..1cb371d 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1324,6 +1324,13 @@
clear_opt(sbi->s_mount_opt, NOBH);
break;
case Opt_extents:
+ if (!EXT4_HAS_INCOMPAT_FEATURE(sb,
+ EXT4_FEATURE_INCOMPAT_EXTENTS)) {
+ ext4_warning(sb, __func__,
+ "extents feature not enabled "
+ "on this filesystem, use tune2fs\n");
+ return 0;
+ }
set_opt (sbi->s_mount_opt, EXTENTS);
break;
case Opt_noextents:
@@ -1997,12 +2004,18 @@
/*
* turn on extents feature by default in ext4 filesystem
- * User -o noextents to turn it off
+ * only if feature flag already set by mkfs or tune2fs.
+ * Use -o noextents to turn it off
*/
- set_opt(sbi->s_mount_opt, EXTENTS);
+ if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_EXTENTS))
+ set_opt(sbi->s_mount_opt, EXTENTS);
+ else
+ ext4_warning(sb, __func__,
+ "extents feature not enabled on this filesystem, "
+ "use tune2fs.\n");
/*
- * turn on mballoc feature by default in ext4 filesystem
- * User -o nomballoc to turn it off
+ * turn on mballoc code by default in ext4 filesystem
+ * Use -o nomballoc to turn it off
*/
set_opt(sbi->s_mount_opt, MBALLOC);