From: Josef Bacik <josef@toxicpanda.com>

Send needs to send the decrypted value of the symlinks, handle the case
where the inode is encrypted and decrypt the symlink name into a buffer
and copy this buffer into our fs_path struct.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Daniel Vacek <neelx@suse.com>
---

v5: https://lore.kernel.org/linux-btrfs/4d97f35d6f85ff041b09bed33b63446a92b7a20c.1706116485.git.josef@toxicpanda.com/
 * read_symlink_encrypted() reworked from using pages to using folios.
---
 fs/btrfs/send.c | 45 ++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 42 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 3dcfdba018b5..b77f96ae2fea 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -1701,9 +1701,7 @@ static int find_extent_clone(struct send_ctx *sctx,
 	return ret;
 }
 
-static int read_symlink(struct btrfs_root *root,
-			u64 ino,
-			struct fs_path *dest)
+static int read_symlink_unencrypted(struct btrfs_root *root, u64 ino, struct fs_path *dest)
 {
 	int ret;
 	BTRFS_PATH_AUTO_FREE(path);
@@ -1764,6 +1762,47 @@ static int read_symlink(struct btrfs_root *root,
 	return fs_path_add_from_extent_buffer(dest, path->nodes[0], off, len);
 }
 
+static int read_symlink_encrypted(struct btrfs_root *root, u64 ino, struct fs_path *dest)
+{
+	DEFINE_DELAYED_CALL(done);
+	const char *buf;
+	struct folio *folio;
+	struct btrfs_inode *inode;
+	int ret = 0;
+
+	inode = btrfs_iget(ino, root);
+	if (IS_ERR(inode))
+		return PTR_ERR(inode);
+
+	folio = read_mapping_folio(inode->vfs_inode.i_mapping, 0, NULL);
+	if (IS_ERR(folio)) {
+		iput(&inode->vfs_inode);
+		return PTR_ERR(folio);
+	}
+
+	buf = fscrypt_get_symlink(&inode->vfs_inode, folio_address(folio),
+				  BTRFS_MAX_INLINE_DATA_SIZE(root->fs_info),
+				  &done);
+	folio_put(folio);
+	iput(&inode->vfs_inode);
+
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+
+	ret = fs_path_add(dest, buf, strlen(buf));
+	do_delayed_call(&done);
+	return ret;
+}
+
+
+static int read_symlink(struct btrfs_root *root, u64 ino,
+			struct fs_path *dest)
+{
+	if (btrfs_fs_incompat(root->fs_info, ENCRYPT))
+		return read_symlink_encrypted(root, ino, dest);
+	return read_symlink_unencrypted(root, ino, dest);
+}
+
 /*
  * Helper function to generate a file name that is unique in the root of
  * send_root and parent_root. This is used to generate names for orphan inodes.
-- 
2.51.0