Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull overlayfs update from Miklos Szeredi:
 "The biggest part of this is making st_dev/st_ino on the overlay behave
  like a normal filesystem (i.e. st_ino doesn't change on copy up,
  st_dev is the same for all files and directories). Currently this only
  works if all layers are on the same filesystem, but future work will
  move the general case towards more sane behavior.

  There are also miscellaneous fixes, including fixes to handling
  append-only files. There's a small change in the VFS, but that only
  has an effect on overlayfs, since otherwise file->f_path.dentry->inode
  and file_inode(file) are always the same"

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: update documentation w.r.t. constant inode numbers
  ovl: persistent inode numbers for upper hardlinks
  ovl: merge getattr for dir and nondir
  ovl: constant st_ino/st_dev across copy up
  ovl: persistent inode number for directories
  ovl: set the ORIGIN type flag
  ovl: lookup non-dir copy-up-origin by file handle
  ovl: use an auxiliary var for overlay root entry
  ovl: store file handle of lower inode on copy up
  ovl: check if all layers are on the same fs
  ovl: do not set overlay.opaque on non-dir create
  ovl: check IS_APPEND() on real upper inode
  vfs: ftruncate check IS_APPEND() on real upper inode
  ovl: Use designated initializers
  ovl: lockdep annotate of nested stacked overlayfs inode lock

1 files changed, 35 insertions, 5 deletions

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index c9e70d39c1ea..9828b7de8999 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -49,11 +49,28 @@ static void ovl_dentry_release(struct dentry *dentry)
 	}
 }
 
+static int ovl_check_append_only(struct inode *inode, int flag)
+{
+	/*
+	 * This test was moot in vfs may_open() because overlay inode does
+	 * not have the S_APPEND flag, so re-check on real upper inode
+	 */
+	if (IS_APPEND(inode)) {
+		if  ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
+			return -EPERM;
+		if (flag & O_TRUNC)
+			return -EPERM;
+	}
+
+	return 0;
+}
+
 static struct dentry *ovl_d_real(struct dentry *dentry,
 				 const struct inode *inode,
 				 unsigned int open_flags)
 {
 	struct dentry *real;
+	int err;
 
 	if (!d_is_reg(dentry)) {
 		if (!inode || inode == d_inode(dentry))
@@ -65,15 +82,20 @@ static struct dentry *ovl_d_real(struct dentry *dentry,
 		return dentry;
 
 	if (open_flags) {
-		int err = ovl_open_maybe_copy_up(dentry, open_flags);
-
+		err = ovl_open_maybe_copy_up(dentry, open_flags);
 		if (err)
 			return ERR_PTR(err);
 	}
 
 	real = ovl_dentry_upper(dentry);
-	if (real && (!inode || inode == d_inode(real)))
+	if (real && (!inode || inode == d_inode(real))) {
+		if (!inode) {
+			err = ovl_check_append_only(d_inode(real), open_flags);
+			if (err)
+				return ERR_PTR(err);
+		}
 		return real;
+	}
 
 	real = ovl_dentry_lower(dentry);
 	if (!real)
@@ -709,8 +731,8 @@ static const struct xattr_handler *ovl_xattr_handlers[] = {
 
 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 {
-	struct path upperpath = { NULL, NULL };
-	struct path workpath = { NULL, NULL };
+	struct path upperpath = { };
+	struct path workpath = { };
 	struct dentry *root_dentry;
 	struct inode *realinode;
 	struct ovl_entry *oe;
@@ -892,11 +914,19 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 
 		ufs->lower_mnt[ufs->numlower] = mnt;
 		ufs->numlower++;
+
+		/* Check if all lower layers are on same sb */
+		if (i == 0)
+			ufs->same_sb = mnt->mnt_sb;
+		else if (ufs->same_sb != mnt->mnt_sb)
+			ufs->same_sb = NULL;
 	}
 
 	/* If the upper fs is nonexistent, we mark overlayfs r/o too */
 	if (!ufs->upper_mnt)
 		sb->s_flags |= MS_RDONLY;
+	else if (ufs->upper_mnt->mnt_sb != ufs->same_sb)
+		ufs->same_sb = NULL;
 
 	if (remote)
 		sb->s_d_op = &ovl_reval_dentry_operations;