ceph: add support for encrypted snapshot names

Since filenames in encrypted directories are encrypted and shown as
a base64-encoded string when the directory is locked, make snapshot
names show a similar behaviour.

When creating a snapshot, .snap directories for every subdirectory will
show the snapshot name in the "long format":

  # mkdir .snap/my-snap
  # ls my-dir/.snap/
  _my-snap_1099511627782

Encrypted snapshots will need to be able to handle these by
encrypting/decrypting only the snapshot part of the string ('my-snap').

Also, since the MDS prevents snapshot names to be bigger than 240
characters it is necessary to adapt CEPH_NOHASH_NAME_MAX to accommodate
this extra limitation.

[ idryomov: drop const on !CONFIG_FS_ENCRYPTION branch too ]

Signed-off-by: Luís Henriques <lhenriques@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Milind Changire <mchangir@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 29 insertions, 4 deletions

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 054fd66609b7..83c420646f90 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -91,9 +91,15 @@ struct inode *ceph_new_inode(struct inode *dir, struct dentry *dentry,
 	if (err < 0)
 		goto out_err;
 
-	err = ceph_fscrypt_prepare_context(dir, inode, as_ctx);
-	if (err)
-		goto out_err;
+	/*
+	 * We'll skip setting fscrypt context for snapshots, leaving that for
+	 * the handle_reply().
+	 */
+	if (ceph_snap(dir) != CEPH_SNAPDIR) {
+		err = ceph_fscrypt_prepare_context(dir, inode, as_ctx);
+		if (err)
+			goto out_err;
+	}
 
 	return inode;
 out_err:
@@ -159,6 +165,7 @@ struct inode *ceph_get_snapdir(struct inode *parent)
 	};
 	struct inode *inode = ceph_get_inode(parent->i_sb, vino, NULL);
 	struct ceph_inode_info *ci = ceph_inode(inode);
+	int ret = -ENOTDIR;
 
 	if (IS_ERR(inode))
 		return inode;
@@ -184,6 +191,24 @@ struct inode *ceph_get_snapdir(struct inode *parent)
 	ci->i_rbytes = 0;
 	ci->i_btime = ceph_inode(parent)->i_btime;
 
+#ifdef CONFIG_FS_ENCRYPTION
+	/* if encrypted, just borrow fscrypt_auth from parent */
+	if (IS_ENCRYPTED(parent)) {
+		struct ceph_inode_info *pci = ceph_inode(parent);
+
+		ci->fscrypt_auth = kmemdup(pci->fscrypt_auth,
+					   pci->fscrypt_auth_len,
+					   GFP_KERNEL);
+		if (ci->fscrypt_auth) {
+			inode->i_flags |= S_ENCRYPTED;
+			ci->fscrypt_auth_len = pci->fscrypt_auth_len;
+		} else {
+			dout("Failed to alloc snapdir fscrypt_auth\n");
+			ret = -ENOMEM;
+			goto err;
+		}
+	}
+#endif
 	if (inode->i_state & I_NEW) {
 		inode->i_op = &ceph_snapdir_iops;
 		inode->i_fop = &ceph_snapdir_fops;
@@ -197,7 +222,7 @@ err:
 		discard_new_inode(inode);
 	else
 		iput(inode);
-	return ERR_PTR(-ENOTDIR);
+	return ERR_PTR(ret);
 }
 
 const struct inode_operations ceph_file_iops = {