[PATCH 1/3] ovl: resurrect ovl_dentry_remote()

[PATCH 1/3] ovl: resurrect ovl_dentry_remote()

[Amir Goldstein]

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---

Miklos,

These patches are against overlayfs-next.
You'd probably want to squash this one.

Thanks,
Amir.

 fs/overlayfs/overlayfs.h | 1 +
 fs/overlayfs/util.c      | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 8db6cf3ffc46..8d67dc7c1c04 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -229,6 +229,7 @@ struct dentry *ovl_indexdir(struct super_block *sb);
 bool ovl_index_all(struct super_block *sb);
 bool ovl_verify_lower(struct super_block *sb);
 struct ovl_entry *ovl_alloc_entry(unsigned int numlower);
+bool ovl_dentry_remote(struct dentry *dentry);
 void ovl_dentry_update_reval(struct dentry *dentry, struct dentry *upperdentry,
 			     unsigned int mask);
 bool ovl_dentry_weird(struct dentry *dentry);
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index ad5770c145ec..0ec3766386b7 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -90,6 +90,12 @@ struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
 	return oe;
 }
 
+bool ovl_dentry_remote(struct dentry *dentry)
+{
+	return dentry->d_flags &
+		(DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE);
+}
+
 void ovl_dentry_update_reval(struct dentry *dentry, struct dentry *upperdentry,
 			     unsigned int mask)
 {
-- 
2.17.1

[PATCH 2/3] ovl: check if upper fs supports RENAME_WHITEOUT

[Amir Goldstein]

As with other required upper fs features, we only warn if support
is missing to avoid breaking existing sub-optimal setups.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/overlayfs/dir.c       |  2 +-
 fs/overlayfs/overlayfs.h |  1 +
 fs/overlayfs/super.c     | 69 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 71 insertions(+), 1 deletion(-)

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index b3471ef51440..c91b5aae8e32 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];
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 8d67dc7c1c04..68df20512dca 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -448,6 +448,7 @@ struct ovl_cattr {
 struct dentry *ovl_create_real(struct inode *dir, struct dentry *newdentry,
 			       struct ovl_cattr *attr);
 int ovl_cleanup(struct inode *dir, struct dentry *dentry);
+struct dentry *ovl_lookup_temp(struct dentry *workdir);
 struct dentry *ovl_create_temp(struct dentry *workdir, struct ovl_cattr *attr);
 
 /* file.c */
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 19c79619529b..7322cf8faea4 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1071,6 +1071,66 @@ static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
 	return err;
 }
 
+/*
+ * Returns 1 if RENAME_WHITEOUT is supported, 0 if not supported and
+ * negative values if error is encountered.
+ */
+static int ovl_check_rename_whiteout(struct dentry *workdir)
+{
+	struct inode *dir = d_inode(workdir);
+	struct dentry *temp;
+	struct dentry *dest;
+	struct dentry *whiteout;
+	struct name_snapshot name;
+	int err;
+
+	inode_lock_nested(dir, I_MUTEX_PARENT);
+
+	temp = ovl_create_temp(workdir, OVL_CATTR(S_IFREG | 0));
+	err = PTR_ERR(temp);
+	if (IS_ERR(temp))
+		goto out_unlock;
+
+	dest = ovl_lookup_temp(workdir);
+	err = PTR_ERR(dest);
+	if (IS_ERR(dest)) {
+		dput(temp);
+		goto out_unlock;
+	}
+
+	/* Name is inline and stable - using snapshot as a copy helper */
+	take_dentry_name_snapshot(&name, temp);
+	err = ovl_do_rename(dir, temp, dir, dest, RENAME_WHITEOUT);
+	if (err) {
+		if (err == -EINVAL)
+			err = 0;
+		goto cleanup_temp;
+	}
+
+	whiteout = lookup_one_len(name.name.name, workdir, name.name.len);
+	err = PTR_ERR(whiteout);
+	if (IS_ERR(whiteout))
+		goto cleanup_temp;
+
+	err = ovl_is_whiteout(whiteout);
+
+	/* Best effort cleanup of whiteout and temp file */
+	if (err)
+		ovl_cleanup(dir, whiteout);
+	dput(whiteout);
+
+cleanup_temp:
+	ovl_cleanup(dir, temp);
+	release_dentry_name_snapshot(&name);
+	dput(temp);
+	dput(dest);
+
+out_unlock:
+	inode_unlock(dir);
+
+	return err;
+}
+
 static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
 			    struct path *workpath)
 {
@@ -1116,6 +1176,15 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
 	else
 		pr_warn("upper fs does not support tmpfile.\n");
 
+
+	/* Check if upper/work fs supports RENAME_WHITEOUT */
+	err = ovl_check_rename_whiteout(ofs->workdir);
+	if (err < 0)
+		goto out;
+
+	if (!err)
+		pr_warn("upper fs does not support RENAME_WHITEOUT.\n");
+
 	/*
 	 * Check if upper/work fs supports trusted.overlay.* xattr
 	 */
-- 
2.17.1

[PATCH 3/3] ovl: strict upper fs requirements for remote upper fs

[Amir Goldstein]

Overlayfs works sub-optimally with upper fs that has no
xattr/d_type/O_TMPFILE/RENAME_WHITEOUT support. We should basically
deprecate support for those filesystems, but so far, we only issue a
warning and don't fail the mount for the sake of backward compat.
Some features are already being disabled with no xattr support.

For newly supported remote upper fs, we do not need to worry about
backward compatibility, so we can fail the mount if upper fs is a
sub-optimal filesystem.

This reduces the in-tree remote filesystems supported as upper to
just FUSE, for which the remote upper fs support was added.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/overlayfs/super.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 7322cf8faea4..6dc45bc7d664 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1136,6 +1136,8 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
 {
 	struct vfsmount *mnt = ofs->upper_mnt;
 	struct dentry *temp;
+	bool rename_whiteout;
+	bool d_type;
 	int fh_type;
 	int err;
 
@@ -1161,11 +1163,8 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
 	if (err < 0)
 		goto out;
 
-	/*
-	 * We allowed this configuration and don't want to break users over
-	 * kernel upgrade. So warn instead of erroring out.
-	 */
-	if (!err)
+	d_type = err;
+	if (!d_type)
 		pr_warn("upper fs needs to support d_type.\n");
 
 	/* Check if upper/work fs supports O_TMPFILE */
@@ -1182,7 +1181,8 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
 	if (err < 0)
 		goto out;
 
-	if (!err)
+	rename_whiteout = err;
+	if (!rename_whiteout)
 		pr_warn("upper fs does not support RENAME_WHITEOUT.\n");
 
 	/*
@@ -1199,6 +1199,18 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
 		vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE);
 	}
 
+	/*
+	 * We allowed sub-optimal upper fs configuration and don't want to break
+	 * users over kernel upgrade, but we never allowed remote upper fs, so
+	 * we can enforce strict requirements for remote upper fs.
+	 */
+	if (ovl_dentry_remote(ofs->workdir) &&
+	    (!d_type || !ofs->tmpfile || !rename_whiteout || ofs->noxattr)) {
+		pr_err("upper fs missing required features.\n");
+		err = -EINVAL;
+		goto out;
+	}
+
 	/* Check if upper/work fs supports file handles */
 	fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
 	if (ofs->config.index && !fh_type) {
-- 
2.17.1