Btrfs: add support for compat flags to btrfs

This adds the necessary disk format for handling compatibility flags
in the future to handle disk format changes.  We have a compat_flags,
compat_ro_flags and incompat_flags set for the super block.  Compat
flags will be to hold the features that are compatible with older
versions of btrfs, compat_ro flags have features that are compatible
with older versions of btrfs if the fs is mounted read only, and
incompat_flags has features that are incompatible with older versions
of btrfs.  This also axes the compat_flags field for the inode and
just makes the flags field a 64bit field, and changes the root item
flags field to 64bit.

Signed-off-by: Josef Bacik <jbacik@redhat.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 2464c099db57..6ae9bdf98b68 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1434,6 +1434,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         u32 blocksize;
         u32 stripesize;
         u64 generation;
+        u64 features;
         struct btrfs_key location;
         struct buffer_head *bh;
         struct btrfs_root *extent_root = kzalloc(sizeof(struct btrfs_root),
@@ -1586,6 +1587,26 @@ struct btrfs_root *open_ctree(struct super_block *sb,
                 goto fail_sb_buffer;
         }
 
+        features = btrfs_super_incompat_flags(disk_super) &
+                ~BTRFS_FEATURE_INCOMPAT_SUPP;
+        if (features) {
+                printk(KERN_ERR "BTRFS: couldn't mount because of "
+                       "unsupported optional features (%Lx).\n",
+                       features);
+                err = -EINVAL;
+                goto fail_sb_buffer;
+        }
+
+        features = btrfs_super_compat_ro_flags(disk_super) &
+                ~BTRFS_FEATURE_COMPAT_RO_SUPP;
+        if (!(sb->s_flags & MS_RDONLY) && features) {
+                printk(KERN_ERR "BTRFS: couldn't mount RDWR because of "
+                       "unsupported option features (%Lx).\n",
+                       features);
+                err = -EINVAL;
+                goto fail_sb_buffer;
+        }
+
         /*
          * we need to start all the end_io workers up front because the
          * queue work function gets called at interrupt time, and so it