Btrfs: Add a special device list for chunk allocations

This allows other code that needs to walk every device in the FS to do so
without locking against allocations.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index dfe7e8a9507c..a2660d2b6b34 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -24,9 +24,12 @@
 struct buffer_head;
 struct btrfs_device {
         struct list_head dev_list;
+        struct list_head dev_alloc_list;
         struct btrfs_root *dev_root;
         struct buffer_head *pending_io;
+
         int barriers;
+
         spinlock_t io_lock;
 
         struct block_device *bdev;
@@ -70,7 +73,11 @@ struct btrfs_fs_devices {
         u64 num_devices;
         struct block_device *latest_bdev;
         struct block_device *lowest_bdev;
+        /* all of the devices in the FS */
         struct list_head devices;
+
+        /* devices not currently being allocated */
+        struct list_head alloc_list;
         struct list_head list;
 };