Merge tag 'ovl-update-5.7' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull overlayfs update from Miklos Szeredi:

 - Fix failure to copy-up files from certain NFSv4 mounts

 - Sort out inconsistencies between st_ino and i_ino (used in /proc/locks)

 - Allow consistent (POSIX-y) inode numbering in more cases

 - Allow virtiofs to be used as upper layer

 - Miscellaneous cleanups and fixes

* tag 'ovl-update-5.7' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: document xino expected behavior
  ovl: enable xino automatically in more cases
  ovl: avoid possible inode number collisions with xino=on
  ovl: use a private non-persistent ino pool
  ovl: fix WARN_ON nlink drop to zero
  ovl: fix a typo in comment
  ovl: replace zero-length array with flexible-array member
  ovl: ovl_obtain_alias(): don't call d_instantiate_anon() for old
  ovl: strict upper fs requirements for remote upper fs
  ovl: check if upper fs supports RENAME_WHITEOUT
  ovl: allow remote upper
  ovl: decide if revalidate needed on a per-dentry basis
  ovl: separate detection of remote upper layer from stacked overlay
  ovl: restructure dentry revalidation
  ovl: ignore failure to copy up unknown xattrs
  ovl: document permission model
  ovl: simplify i_ino initialization
  ovl: factor out helper ovl_get_root()
  ovl: fix out of date comment and unreachable code
  ovl: fix value of i_ino for lower hardlink corner case

1 files changed, 28 insertions, 3 deletions

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 8e57d5372b8f..279009dee366 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -42,7 +42,7 @@ int ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
 	return err;
 }
 
-static struct dentry *ovl_lookup_temp(struct dentry *workdir)
+struct dentry *ovl_lookup_temp(struct dentry *workdir)
 {
 	struct dentry *temp;
 	char name[20];
@@ -243,6 +243,9 @@ static int ovl_instantiate(struct dentry *dentry, struct inode *inode,
 
 	ovl_dir_modified(dentry->d_parent, false);
 	ovl_dentry_set_upper_alias(dentry);
+	ovl_dentry_update_reval(dentry, newdentry,
+			DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE);
+
 	if (!hardlink) {
 		/*
 		 * ovl_obtain_alias() can be called after ovl_create_real()
@@ -819,6 +822,28 @@ static bool ovl_pure_upper(struct dentry *dentry)
 	       !ovl_test_flag(OVL_WHITEOUTS, d_inode(dentry));
 }
 
+static void ovl_drop_nlink(struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+	struct dentry *alias;
+
+	/* Try to find another, hashed alias */
+	spin_lock(&inode->i_lock);
+	hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
+		if (alias != dentry && !d_unhashed(alias))
+			break;
+	}
+	spin_unlock(&inode->i_lock);
+
+	/*
+	 * Changes to underlying layers may cause i_nlink to lose sync with
+	 * reality.  In this case prevent the link count from going to zero
+	 * prematurely.
+	 */
+	if (inode->i_nlink > !!alias)
+		drop_nlink(inode);
+}
+
 static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 {
 	int err;
@@ -856,7 +881,7 @@ static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 		if (is_dir)
 			clear_nlink(dentry->d_inode);
 		else
-			drop_nlink(dentry->d_inode);
+			ovl_drop_nlink(dentry);
 	}
 	ovl_nlink_end(dentry);
 
@@ -1201,7 +1226,7 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
 		if (new_is_dir)
 			clear_nlink(d_inode(new));
 		else
-			drop_nlink(d_inode(new));
+			ovl_drop_nlink(new);
 	}
 
 	ovl_dir_modified(old->d_parent, ovl_type_origin(old) ||