1 files changed, 31 insertions, 2 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 0b4e2af7954d..ef41f285a475 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -459,12 +459,23 @@ int btrfs_close_extra_devices(struct btrfs_fs_devices *fs_devices)
 {
         struct btrfs_device *device, *next;
 
+        struct block_device *latest_bdev = NULL;
+        u64 latest_devid = 0;
+        u64 latest_transid = 0;
+
         mutex_lock(&uuid_mutex);
 again:
         /* This is the initialized path, it is safe to release the devices. */
         list_for_each_entry_safe(device, next, &fs_devices->devices, dev_list) {
-                if (device->in_fs_metadata)
+                if (device->in_fs_metadata) {
+                        if (!latest_transid ||
+                            device->generation > latest_transid) {
+                                latest_devid = device->devid;
+                                latest_transid = device->generation;
+                                latest_bdev = device->bdev;
+                        }
                         continue;
+                }
 
                 if (device->bdev) {
                         blkdev_put(device->bdev, device->mode);
@@ -487,6 +498,10 @@ again:
                 goto again;
         }
 
+        fs_devices->latest_bdev = latest_bdev;
+        fs_devices->latest_devid = latest_devid;
+        fs_devices->latest_trans = latest_transid;
+
         mutex_unlock(&uuid_mutex);
         return 0;
 }
@@ -1953,7 +1968,7 @@ static int btrfs_relocate_chunk(struct btrfs_root *root,
         em = lookup_extent_mapping(em_tree, chunk_offset, 1);
         read_unlock(&em_tree->lock);
 
-        BUG_ON(em->start > chunk_offset ||
+        BUG_ON(!em || em->start > chunk_offset ||
                em->start + em->len < chunk_offset);
         map = (struct map_lookup *)em->bdev;
 
@@ -4356,6 +4371,20 @@ int btrfs_read_sys_array(struct btrfs_root *root)
                 return -ENOMEM;
         btrfs_set_buffer_uptodate(sb);
         btrfs_set_buffer_lockdep_class(root->root_key.objectid, sb, 0);
+        /*
+         * The sb extent buffer is artifical and just used to read the system array.
+         * btrfs_set_buffer_uptodate() call does not properly mark all it's
+         * pages up-to-date when the page is larger: extent does not cover the
+         * whole page and consequently check_page_uptodate does not find all
+         * the page's extents up-to-date (the hole beyond sb),
+         * write_extent_buffer then triggers a WARN_ON.
+         *
+         * Regular short extents go through mark_extent_buffer_dirty/writeback cycle,
+         * but sb spans only this function. Add an explicit SetPageUptodate call
+         * to silence the warning eg. on PowerPC 64.
+         */
+        if (PAGE_CACHE_SIZE > BTRFS_SUPER_INFO_SIZE)
+                SetPageUptodate(sb->first_page);
 
         write_extent_buffer(sb, super_copy, 0, BTRFS_SUPER_INFO_SIZE);
         array_size = btrfs_super_sys_array_size(super_copy);