[PATCH 13/15] btrfs: provide framework to get and put a spare device

[Anand Jain]

This adds functions to get and put a spare device from the list.
So that hot repace code can pick a spare device when needed.

Signed-off-by: Anand Jain <anand.j...@oracle.com>
---
 fs/btrfs/super.c   |  9 +++++++++
 fs/btrfs/volumes.c | 37 +++++++++++++++++++++++++++++++++++++
 fs/btrfs/volumes.h |  2 ++
 3 files changed, 48 insertions(+)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index d495790..29836ca 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2035,6 +2035,15 @@ static int btrfs_control_open(struct inode *inode, 
struct file *file)
        return 0;
 }
 
+void btrfs_put_spare_device(char *path)
+{
+       struct btrfs_fs_devices *fs_devices;
+
+       if (btrfs_scan_one_device(path, FMODE_READ,
+                                   &btrfs_fs_type, &fs_devices))
+               printk(KERN_INFO "failed to return spare device\n");
+}
+
 /*
  * used by btrfsctl to scan devices when no FS is mounted
  */
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 28f549d..3b90690 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -7017,3 +7017,40 @@ void btrfs_force_device_close(struct btrfs_device *dev, 
char *why)
                rcu_str_deref(dev->name), why);
        rcu_read_unlock();
 }
+
+int btrfs_get_spare_device(char **path)
+{
+       int ret = 1;
+       struct btrfs_fs_devices *fs_devices;
+       struct btrfs_device *device;
+       struct list_head *fs_uuids = btrfs_get_fs_uuids();
+
+       mutex_lock(&uuid_mutex);
+       list_for_each_entry(fs_devices, fs_uuids, list) {
+               if (!fs_devices->spare)
+                       continue;
+
+               /* as of now there is only one device in the spare fs_devices */
+               device = list_entry(fs_devices->devices.next,
+                                       struct btrfs_device, dev_list);
+
+               if (!device || !device->name)
+                       continue;
+
+               fs_devices->spare = 0;
+               rcu_read_lock();
+               *path = kstrdup(device->name->str, GFP_NOFS);
+               rcu_read_unlock();
+               ret = 0;
+               break;
+       }
+
+       if (!ret) {
+               btrfs_sysfs_remove_fsid(fs_devices);
+               list_del(&fs_devices->list);
+               free_fs_devices(fs_devices);
+       }
+       mutex_unlock(&uuid_mutex);
+
+       return ret;
+}
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 3d995b7..36184ec 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -577,5 +577,7 @@ void btrfs_reset_fs_info_ptr(struct btrfs_fs_info *fs_info);
 void btrfs_close_one_device(struct btrfs_device *device);
 int btrfs_check_degradable(struct btrfs_fs_info *fs_info, unsigned flags);
 void btrfs_force_device_close(struct btrfs_device *dev, char *why);
+int btrfs_get_spare_device(char **path);
+void btrfs_put_spare_device(char *path);
 
 #endif
-- 
2.4.1

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