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/ialloc.c b/fs/ext4/ialloc.c
index 8b0a10a..a92eb30 100644 (file)
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -836,14 +836,10 @@ got:
                goto fail_free_drop;
 
        if (test_opt(sb, EXTENTS)) {
-               /* set extent flag only for diretory, file and normal symlink*/
+               /* set extent flag only for directory, file and normal symlink*/
                if (S_ISDIR(mode) || S_ISREG(mode) || S_ISLNK(mode)) {
                        EXT4_I(inode)->i_flags |= EXT4_EXTENTS_FL;
                        ext4_ext_tree_init(handle, inode);
-                       err = ext4_update_incompat_feature(handle, sb,
-                                       EXT4_FEATURE_INCOMPAT_EXTENTS);
-                       if (err)
-                               goto fail_free_drop;
                }
        }
 

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 2bf9cdd..1cb371d 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1324,6 +1324,13 @@ set_qf_format:
                        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 @@ static int ext4_fill_super (struct super_block *sb, void *data, int silent)
 
        /*
         * 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);