Btrfs: shared seed device

This patch makes seed device possible to be shared by
multiple mounted file systems. The sharing is achieved
by cloning seed device's btrfs_fs_devices structure.
Thanks you,

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

1 files changed, 18 insertions, 19 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 1cc89246ee2f..171057a32679 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -218,7 +218,7 @@ static int cache_block_group(struct btrfs_root *root,
         struct btrfs_key key;
         struct extent_buffer *leaf;
         int slot;
-        u64 last = block_group->key.objectid;
+        u64 last;
 
         if (!block_group)
                 return 0;
@@ -239,7 +239,8 @@ static int cache_block_group(struct btrfs_root *root,
          * skip the locking here
          */
         path->skip_locking = 1;
-        key.objectid = max_t(u64, last, BTRFS_SUPER_INFO_OFFSET);
+        last = max_t(u64, block_group->key.objectid, BTRFS_SUPER_INFO_OFFSET);
+        key.objectid = last;
         key.offset = 0;
         btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
@@ -5335,8 +5336,20 @@ static int noinline relocate_one_extent(struct btrfs_root *extent_root,
                         prev_block = block_start;
                 }
 
-                if (ref_path->owner_objectid >= BTRFS_FIRST_FREE_OBJECTID &&
-                    pass >= 2) {
+                btrfs_record_root_in_trans(found_root);
+                if (ref_path->owner_objectid >= BTRFS_FIRST_FREE_OBJECTID) {
+                        /*
+                         * try to update data extent references while
+                         * keeping metadata shared between snapshots.
+                         */
+                        if (pass == 1) {
+                                ret = relocate_one_path(trans, found_root,
+                                                path, &first_key, ref_path,
+                                                group, reloc_inode);
+                                if (ret < 0)
+                                        goto out;
+                                continue;
+                        }
                         /*
                          * use fallback method to process the remaining
                          * references.
@@ -5359,23 +5372,9 @@ static int noinline relocate_one_extent(struct btrfs_root *extent_root,
                                                 path, extent_key,
                                                 &first_key, ref_path,
                                                 new_extents, nr_extents);
-                        if (ret < 0)
-                                goto out;
-                        continue;
-                }
-
-                btrfs_record_root_in_trans(found_root);
-                if (ref_path->owner_objectid < BTRFS_FIRST_FREE_OBJECTID) {
+                } else {
                         ret = relocate_tree_block(trans, found_root, path,
                                                   &first_key, ref_path);
-                } else {
-                        /*
-                         * try to update data extent references while
-                         * keeping metadata shared between snapshots.
-                         */
-                        ret = relocate_one_path(trans, found_root, path,
-                                                &first_key, ref_path,
-                                                group, reloc_inode);
                 }
                 if (ret < 0)
                         goto out;