locks: break delegations on rename

Cc: David Howells <dhowells@redhat.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 43 insertions, 4 deletions

diff --git a/fs/namei.c b/fs/namei.c
index cfaeaae0f2db..ce7e580e4e14 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4022,7 +4022,8 @@ out:
 }
 
 static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
-                            struct inode *new_dir, struct dentry *new_dentry)
+                            struct inode *new_dir, struct dentry *new_dentry,
+                            struct inode **delegated_inode)
 {
         struct inode *target = new_dentry->d_inode;
         struct inode *source = old_dentry->d_inode;
@@ -4039,6 +4040,14 @@ static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
         if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
                 goto out;
 
+        error = try_break_deleg(source, delegated_inode);
+        if (error)
+                goto out;
+        if (target) {
+                error = try_break_deleg(target, delegated_inode);
+                if (error)
+                        goto out;
+        }
         error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
         if (error)
                 goto out;
@@ -4053,8 +4062,30 @@ out:
         return error;
 }
 
+/**
+ * vfs_rename - rename a filesystem object
+ * @old_dir:    parent of source
+ * @old_dentry: source
+ * @new_dir:    parent of destination
+ * @new_dentry: destination
+ * @delegated_inode: returns an inode needing a delegation break
+ *
+ * The caller must hold multiple mutexes--see lock_rename()).
+ *
+ * If vfs_rename discovers a delegation in need of breaking at either
+ * the source or destination, it will return -EWOULDBLOCK and return a
+ * reference to the inode in delegated_inode.  The caller should then
+ * break the delegation and retry.  Because breaking a delegation may
+ * take a long time, the caller should drop all locks before doing
+ * so.
+ *
+ * Alternatively, a caller may pass NULL for delegated_inode.  This may
+ * be appropriate for callers that expect the underlying filesystem not
+ * to be NFS exported.
+ */
 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
-               struct inode *new_dir, struct dentry *new_dentry)
+               struct inode *new_dir, struct dentry *new_dentry,
+               struct inode **delegated_inode)
 {
         int error;
         int is_dir = d_is_directory(old_dentry) || d_is_autodir(old_dentry);
@@ -4082,7 +4113,7 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
         if (is_dir)
                 error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
         else
-                error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
+                error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry,delegated_inode);
         if (!error)
                 fsnotify_move(old_dir, new_dir, old_name, is_dir,
                               new_dentry->d_inode, old_dentry);
@@ -4098,6 +4129,7 @@ SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
         struct dentry *old_dentry, *new_dentry;
         struct dentry *trap;
         struct nameidata oldnd, newnd;
+        struct inode *delegated_inode = NULL;
         struct filename *from;
         struct filename *to;
         unsigned int lookup_flags = 0;
@@ -4137,6 +4169,7 @@ retry:
         newnd.flags &= ~LOOKUP_PARENT;
         newnd.flags |= LOOKUP_RENAME_TARGET;
 
+retry_deleg:
         trap = lock_rename(new_dir, old_dir);
 
         old_dentry = lookup_hash(&oldnd);
@@ -4173,13 +4206,19 @@ retry:
         if (error)
                 goto exit5;
         error = vfs_rename(old_dir->d_inode, old_dentry,
-                                   new_dir->d_inode, new_dentry);
+                                   new_dir->d_inode, new_dentry,
+                                   &delegated_inode);
 exit5:
         dput(new_dentry);
 exit4:
         dput(old_dentry);
 exit3:
         unlock_rename(new_dir, old_dir);
+        if (delegated_inode) {
+                error = break_deleg_wait(&delegated_inode);
+                if (!error)
+                        goto retry_deleg;
+        }
         mnt_drop_write(oldnd.path.mnt);
 exit2:
         if (retry_estale(error, lookup_flags))