nfs_complete_rename() calls d_move() without i_mutex

This reverts commit 920b4530fb80430ff30ef83efe21ba1fa5623731 which could call d_move() without holding the directory's i_mutex, and reverts commit d4ea7e3c5c0e341c15b073016dbf3ab6c65f12f3 "NFS: Fix old dentry rehash after move", which was a follow-up fix.

Fixes 920b4530fb80 ("NFS: nfs_rename() handle -ERESTARTSYS dentry left behind")

Cc [email protected] # v4.10+

---
 fs/nfs/dir.c | 45 ++++++++++++++++++---------------------------
 1 file changed, 18 insertions(+), 27 deletions(-)

fs/nfs/dir.c +9 -27

index 32ccd7754f8a..1faf337b316f 100644
@@ -1946,29 +1946,6 @@ nfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
 }
 EXPORT_SYMBOL_GPL(nfs_link);
 
-static void
-nfs_complete_rename(struct rpc_task *task, struct nfs_renamedata *data)
-{
-	struct dentry *old_dentry = data->old_dentry;
-	struct dentry *new_dentry = data->new_dentry;
-	struct inode *old_inode = d_inode(old_dentry);
-	struct inode *new_inode = d_inode(new_dentry);
-
-	nfs_mark_for_revalidate(old_inode);
-
-	switch (task->tk_status) {
-	case 0:
-		if (new_inode != NULL)
-			nfs_drop_nlink(new_inode);
-		d_move(old_dentry, new_dentry);
-		nfs_set_verifier(new_dentry,
-					nfs_save_change_attribute(data->new_dir));
-		break;
-	case -ENOENT:
-		nfs_dentry_handle_enoent(old_dentry);
-	}
-}
-
 /*
  * RENAME
  * FIXME: Some nfsds, like the Linux user space nfsd, may generate a

@@ -1999,7 +1976,7 @@ int nfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 {
 	struct inode *old_inode = d_inode(old_dentry);
 	struct inode *new_inode = d_inode(new_dentry);
-	struct dentry *dentry = NULL;
+	struct dentry *dentry = NULL, *rehash = NULL;
 	struct rpc_task *task;
 	int error = -EBUSY;
 

@@ -2022,8 +1999,10 @@ int nfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 		 * To prevent any new references to the target during the
 		 * rename, we unhash the dentry in advance.
 		 */
-		if (!d_unhashed(new_dentry))
+		if (!d_unhashed(new_dentry)) {
 			d_drop(new_dentry);
+			rehash = new_dentry;
+		}
 
 		if (d_count(new_dentry) > 2) {
 			int err;

@@ -2040,6 +2019,7 @@ int nfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 				goto out;
 
 			new_dentry = dentry;
+			rehash = NULL;
 			new_inode = NULL;
 		}
 	}

@@ -2048,8 +2028,7 @@ int nfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 	if (new_inode != NULL)
 		NFS_PROTO(new_inode)->return_delegation(new_inode);
 
-	task = nfs_async_rename(old_dir, new_dir, old_dentry, new_dentry,
-					nfs_complete_rename);
+	task = nfs_async_rename(old_dir, new_dir, old_dentry, new_dentry, NULL);
 	if (IS_ERR(task)) {
 		error = PTR_ERR(task);
 		goto out;

@@ -2059,9 +2038,21 @@ int nfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 	if (error == 0)
 		error = task->tk_status;
 	rpc_put_task(task);
+	nfs_mark_for_revalidate(old_inode);
 out:
+	if (rehash)
+		d_rehash(rehash);
 	trace_nfs_rename_exit(old_dir, old_dentry,

An interrupted rename will leave the old dentry behind if the rename succeeds. Fix this by forcing a lookup the next time through ->d_revalidate.

A previous attempt at solving this problem took the approach to complete the work of the rename asynchronously, however that approach was wrong since it would allow the d_move() to occur after the directory's i_mutex had been dropped by the original process.

v2: Add memory barrier, hold directory i_locks while revalidating, specify
single-bit field width for cancelled flag.

Signed-off-by Benjamin Coddington <[email protected]>

---
 fs/nfs/dir.c            |  5 ++++-
 fs/nfs/unlink.c         | 11 +++++++++++
 include/linux/nfs_xdr.h |  1 +
 3 files changed, 16 insertions(+), 1 deletion(-)

fs/nfs/dir.c +0 -0

index 1faf337b316f..94b05d0eec06 100644

fs/nfs/dir.c +1 -0

+	} else
 		error = task->tk_status;
 	rpc_put_task(task);
 	nfs_mark_for_revalidate(old_inode);

fs/nfs/unlink.c +11 -0

index 191aa577dd1f..28628dde38b9 100644
@@ -288,6 +288,17 @@ static void nfs_async_rename_release(void *calldata)
 	if (d_really_is_positive(data->old_dentry))
 		nfs_mark_for_revalidate(d_inode(data->old_dentry));
 
+	/* The result of the rename is unknown. Play it safe by
+	 * forcing a new lookup */
+	if (data->cancelled) {
+		spin_lock(&data->old_dir->i_lock);
+		nfs_force_lookup_revalidate(data->old_dir);
+		spin_unlock(&data->old_dir->i_lock);
+		spin_lock(&data->new_dir->i_lock);
+		nfs_force_lookup_revalidate(data->new_dir);
+		spin_unlock(&data->new_dir->i_lock);
+	}
+
 	dput(data->old_dentry);
 	dput(data->new_dentry);
 	iput(data->old_dir);

include/linux/nfs_xdr.h +0 -0

index b28c83475ee8..0c32443d29a7 100644