1 files changed, 101 insertions, 6 deletions

diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
index 24fb8ce4e071..6bb465cca20f 100644
--- a/fs/btrfs/root-tree.c
+++ b/fs/btrfs/root-tree.c
@@ -16,12 +16,55 @@
  * Boston, MA 021110-1307, USA.
  */
 
+#include <linux/uuid.h>
 #include "ctree.h"
 #include "transaction.h"
 #include "disk-io.h"
 #include "print-tree.h"
 
 /*
+ * Read a root item from the tree. In case we detect a root item smaller then
+ * sizeof(root_item), we know it's an old version of the root structure and
+ * initialize all new fields to zero. The same happens if we detect mismatching
+ * generation numbers as then we know the root was once mounted with an older
+ * kernel that was not aware of the root item structure change.
+ */
+void btrfs_read_root_item(struct btrfs_root *root,
+                         struct extent_buffer *eb, int slot,
+                         struct btrfs_root_item *item)
+{
+        uuid_le uuid;
+        int len;
+        int need_reset = 0;
+
+        len = btrfs_item_size_nr(eb, slot);
+        read_extent_buffer(eb, item, btrfs_item_ptr_offset(eb, slot),
+                        min_t(int, len, (int)sizeof(*item)));
+        if (len < sizeof(*item))
+                need_reset = 1;
+        if (!need_reset && btrfs_root_generation(item)
+                != btrfs_root_generation_v2(item)) {
+                if (btrfs_root_generation_v2(item) != 0) {
+                        printk(KERN_WARNING "btrfs: mismatching "
+                                        "generation and generation_v2 "
+                                        "found in root item. This root "
+                                        "was probably mounted with an "
+                                        "older kernel. Resetting all "
+                                        "new fields.\n");
+                }
+                need_reset = 1;
+        }
+        if (need_reset) {
+                memset(&item->generation_v2, 0,
+                        sizeof(*item) - offsetof(struct btrfs_root_item,
+                                        generation_v2));
+
+                uuid_le_gen(&uuid);
+                memcpy(item->uuid, uuid.b, BTRFS_UUID_SIZE);
+        }
+}
+
+/*
  * lookup the root with the highest offset for a given objectid.  The key we do
  * find is copied into 'key'.  If we find something return 0, otherwise 1, < 0
  * on error.
@@ -61,10 +104,10 @@ int btrfs_find_last_root(struct btrfs_root *root, u64 objectid,
                 goto out;
         }
         if (item)
-                read_extent_buffer(l, item, btrfs_item_ptr_offset(l, slot),
-                                   sizeof(*item));
+                btrfs_read_root_item(root, l, slot, item);
         if (key)
                 memcpy(key, &found_key, sizeof(found_key));
+
         ret = 0;
 out:
         btrfs_free_path(path);
@@ -91,16 +134,15 @@ int btrfs_update_root(struct btrfs_trans_handle *trans, struct btrfs_root
         int ret;
         int slot;
         unsigned long ptr;
+        int old_len;
 
         path = btrfs_alloc_path();
         if (!path)
                 return -ENOMEM;
 
         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
-        if (ret < 0) {
-                btrfs_abort_transaction(trans, root, ret);
-                goto out;
-        }
+        if (ret < 0)
+                goto out_abort;
 
         if (ret != 0) {
                 btrfs_print_leaf(root, path->nodes[0]);
@@ -113,16 +155,56 @@ int btrfs_update_root(struct btrfs_trans_handle *trans, struct btrfs_root
         l = path->nodes[0];
         slot = path->slots[0];
         ptr = btrfs_item_ptr_offset(l, slot);
+        old_len = btrfs_item_size_nr(l, slot);
+
+        /*
+         * If this is the first time we update the root item which originated
+         * from an older kernel, we need to enlarge the item size to make room
+         * for the added fields.
+         */
+        if (old_len < sizeof(*item)) {
+                btrfs_release_path(path);
+                ret = btrfs_search_slot(trans, root, key, path,
+                                -1, 1);
+                if (ret < 0)
+                        goto out_abort;
+                ret = btrfs_del_item(trans, root, path);
+                if (ret < 0)
+                        goto out_abort;
+                btrfs_release_path(path);
+                ret = btrfs_insert_empty_item(trans, root, path,
+                                key, sizeof(*item));
+                if (ret < 0)
+                        goto out_abort;
+                l = path->nodes[0];
+                slot = path->slots[0];
+                ptr = btrfs_item_ptr_offset(l, slot);
+        }
+
+        /*
+         * Update generation_v2 so at the next mount we know the new root
+         * fields are valid.
+         */
+        btrfs_set_root_generation_v2(item, btrfs_root_generation(item));
+
         write_extent_buffer(l, item, ptr, sizeof(*item));
         btrfs_mark_buffer_dirty(path->nodes[0]);
 out:
         btrfs_free_path(path);
         return ret;
+
+out_abort:
+        btrfs_abort_transaction(trans, root, ret);
+        goto out;
 }
 
 int btrfs_insert_root(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                       struct btrfs_key *key, struct btrfs_root_item *item)
 {
+        /*
+         * Make sure generation v1 and v2 match. See update_root for details.
+         */
+        btrfs_set_root_generation_v2(item, btrfs_root_generation(item));
         return btrfs_insert_item(trans, root, key, item, sizeof(*item));
 }
 
@@ -454,3 +536,16 @@ void btrfs_check_and_init_root_item(struct btrfs_root_item *root_item)
                 root_item->byte_limit = 0;
         }
 }
+
+void btrfs_update_root_times(struct btrfs_trans_handle *trans,
+                             struct btrfs_root *root)
+{
+        struct btrfs_root_item *item = &root->root_item;
+        struct timespec ct = CURRENT_TIME;
+
+        spin_lock(&root->root_times_lock);
+        item->ctransid = trans->transid;
+        item->ctime.sec = cpu_to_le64(ct.tv_sec);
+        item->ctime.nsec = cpu_to_le64(ct.tv_nsec);
+        spin_unlock(&root->root_times_lock);
+}