Btrfs: add two more find_device() methods

The new function btrfs_find_device_missing_or_by_path() will be
used for the device replace procedure. This function itself calls
the second new function btrfs_find_device_by_path().
Unfortunately, it is not possible to currently make the rest of the
code use these functions as well, since all functions that look
similar at first view are all a little bit different in what they
are doing. But in the future, new code could benefit from these
two new functions, and currently, device replace uses them.

Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

2 files changed, 64 insertions, 0 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 4def1fdbf755..1483041eb86a 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1522,6 +1522,65 @@ error_undo:
         goto error_brelse;
 }
 
+int btrfs_find_device_by_path(struct btrfs_root *root, char *device_path,
+                              struct btrfs_device **device)
+{
+        int ret = 0;
+        struct btrfs_super_block *disk_super;
+        u64 devid;
+        u8 *dev_uuid;
+        struct block_device *bdev;
+        struct buffer_head *bh;
+
+        *device = NULL;
+        ret = btrfs_get_bdev_and_sb(device_path, FMODE_READ,
+                                    root->fs_info->bdev_holder, 0, &bdev, &bh);
+        if (ret)
+                return ret;
+        disk_super = (struct btrfs_super_block *)bh->b_data;
+        devid = btrfs_stack_device_id(&disk_super->dev_item);
+        dev_uuid = disk_super->dev_item.uuid;
+        *device = btrfs_find_device(root, devid, dev_uuid,
+                                    disk_super->fsid);
+        brelse(bh);
+        if (!*device)
+                ret = -ENOENT;
+        blkdev_put(bdev, FMODE_READ);
+        return ret;
+}
+
+int btrfs_find_device_missing_or_by_path(struct btrfs_root *root,
+                                         char *device_path,
+                                         struct btrfs_device **device)
+{
+        *device = NULL;
+        if (strcmp(device_path, "missing") == 0) {
+                struct list_head *devices;
+                struct btrfs_device *tmp;
+
+                devices = &root->fs_info->fs_devices->devices;
+                /*
+                 * It is safe to read the devices since the volume_mutex
+                 * is held by the caller.
+                 */
+                list_for_each_entry(tmp, devices, dev_list) {
+                        if (tmp->in_fs_metadata && !tmp->bdev) {
+                                *device = tmp;
+                                break;
+                        }
+                }
+
+                if (!*device) {
+                        pr_err("btrfs: no missing device found\n");
+                        return -ENOENT;
+                }
+
+                return 0;
+        } else {
+                return btrfs_find_device_by_path(root, device_path, device);
+        }
+}
+
 /*
  * does all the dirty work required for changing file system's UUID.
  */
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 1789cda57efb..657bb12b3069 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -268,6 +268,11 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
                           struct btrfs_fs_devices **fs_devices_ret);
 int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
 void btrfs_close_extra_devices(struct btrfs_fs_devices *fs_devices);
+int btrfs_find_device_missing_or_by_path(struct btrfs_root *root,
+                                         char *device_path,
+                                         struct btrfs_device **device);
+int btrfs_find_device_by_path(struct btrfs_root *root, char *device_path,
+                              struct btrfs_device **device);
 int btrfs_add_device(struct btrfs_trans_handle *trans,
                      struct btrfs_root *root,
                      struct btrfs_device *device);