fs: btrfs: Introduce function to resolve path in one subvolume

This patch introduces a new function, get_path_in_subvolume(), which
resolves inode number into path inside a subvolume.

This function will be later used for btrfs subvolume list functionality.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Marek Behún <marek.behun@nic.cz>

diff --git a/fs/btrfs/compat.h b/fs/btrfs/compat.h
index dbb3395..9cf8a10 100644 (file)
--- a/fs/btrfs/compat.h
+++ b/fs/btrfs/compat.h
@@ -18,6 +18,7 @@
 
 /* No <linux/limits.h> so have to define it here */
 #define XATTR_NAME_MAX         255
+#define PATH_MAX               4096
 
 /*
  * Macros to generate set/get funcs for the struct fields

diff --git a/fs/btrfs/subvolume.c b/fs/btrfs/subvolume.c
index 0e72577..b446e72 100644 (file)
--- a/fs/btrfs/subvolume.c
+++ b/fs/btrfs/subvolume.c
@@ -5,8 +5,74 @@
  * 2017 Marek Behun, CZ.NIC, marek.behun@nic.cz
  */
 
-#include "btrfs.h"
 #include <malloc.h>
+#include "ctree.h"
+#include "btrfs.h"
+
+/*
+ * Resolve the path of ino inside subvolume @root into @path_ret.
+ *
+ * @path_ret must be at least PATH_MAX size.
+ */
+static int get_path_in_subvol(struct btrfs_root *root, u64 ino, char *path_ret)
+{
+       struct btrfs_path path;
+       struct btrfs_key key;
+       char *tmp;
+       u64 cur = ino;
+       int ret = 0;
+
+       tmp = malloc(PATH_MAX);
+       if (!tmp)
+               return -ENOMEM;
+       tmp[0] = '\0';
+
+       btrfs_init_path(&path);
+       while (cur != BTRFS_FIRST_FREE_OBJECTID) {
+               struct btrfs_inode_ref *iref;
+               int name_len;
+
+               btrfs_release_path(&path);
+               key.objectid = cur;
+               key.type = BTRFS_INODE_REF_KEY;
+               key.offset = (u64)-1;
+
+               ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
+               /* Impossible */
+               if (ret == 0)
+                       ret = -EUCLEAN;
+               if (ret < 0)
+                       goto out;
+               ret = btrfs_previous_item(root, &path, cur,
+                                         BTRFS_INODE_REF_KEY);
+               if (ret > 0)
+                       ret = -ENOENT;
+               if (ret < 0)
+                       goto out;
+
+               strncpy(tmp, path_ret, PATH_MAX);
+               iref = btrfs_item_ptr(path.nodes[0], path.slots[0],
+                                     struct btrfs_inode_ref);
+               name_len = btrfs_inode_ref_name_len(path.nodes[0],
+                                                   iref);
+               if (name_len > BTRFS_NAME_LEN) {
+                       ret = -ENAMETOOLONG;
+                       goto out;
+               }
+               read_extent_buffer(path.nodes[0], path_ret,
+                                  (unsigned long)(iref + 1), name_len);
+               path_ret[name_len] = '/';
+               path_ret[name_len + 1] = '\0';
+               strncat(path_ret, tmp, PATH_MAX);
+
+               btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
+               cur = key.offset;
+       }
+out:
+       btrfs_release_path(&path);
+       free(tmp);
+       return ret;
+}
 
 static int get_subvol_name(u64 subvolid, char *name, int max_len)
 {