Btrfs: Give each subvol and snapshot their own anonymous devid

Each subvolume has its own private inode number space, and so we need
to fill in different device numbers for each subvolume to avoid confusing
applications.

This commit puts a struct super_block into struct btrfs_root so it can
call set_anon_super() and get a different device number generated for
each root.

btrfs_rename is changed to prevent renames across subvols.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 13 insertions, 2 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index e163b1b74707..7ef79ce86e25 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2212,7 +2212,12 @@ static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
         struct btrfs_trans_handle *trans;
         unsigned long nr = 0;
 
-        if (inode->i_size > BTRFS_EMPTY_DIR_SIZE) {
+        /*
+         * the FIRST_FREE_OBJECTID check makes sure we don't try to rmdir
+         * the root of a subvolume or snapshot
+         */
+        if (inode->i_size > BTRFS_EMPTY_DIR_SIZE ||
+            inode->i_ino == BTRFS_FIRST_FREE_OBJECTID) {
                 return -ENOTEMPTY;
         }
 
@@ -4410,7 +4415,6 @@ int btrfs_create_subvol_root(struct btrfs_root *new_root, struct dentry *dentry,
         if (error)
                 return error;
 
-        atomic_inc(&inode->i_count);
         d_instantiate(dentry, inode);
         return 0;
 }
@@ -4548,6 +4552,7 @@ static int btrfs_getattr(struct vfsmount *mnt,
 {
         struct inode *inode = dentry->d_inode;
         generic_fillattr(inode, stat);
+        stat->dev = BTRFS_I(inode)->root->anon_super.s_dev;
         stat->blksize = PAGE_CACHE_SIZE;
         stat->blocks = (inode_get_bytes(inode) +
                         BTRFS_I(inode)->delalloc_bytes) >> 9;
@@ -4565,6 +4570,11 @@ static int btrfs_rename(struct inode * old_dir, struct dentry *old_dentry,
         u64 index = 0;
         int ret;
 
+        /* we're not allowed to rename between subvolumes */
+        if (BTRFS_I(old_inode)->root->root_key.objectid !=
+            BTRFS_I(new_dir)->root->root_key.objectid)
+                return -EXDEV;
+
         if (S_ISDIR(old_inode->i_mode) && new_inode &&
             new_inode->i_size > BTRFS_EMPTY_DIR_SIZE) {
                 return -ENOTEMPTY;
@@ -4920,6 +4930,7 @@ static int btrfs_permission(struct inode *inode, int mask)
 }
 
 static struct inode_operations btrfs_dir_inode_operations = {
+        .getattr        = btrfs_getattr,
         .lookup         = btrfs_lookup,
         .create         = btrfs_create,
         .unlink         = btrfs_unlink,