allow the temp files created by open() to be linked to

O_TMPFILE | O_CREAT => linkat() with AT_SYMLINK_FOLLOW and /proc/self/fd/<n>
as oldpath (i.e. flink()) will create a link
O_TMPFILE | O_CREAT | O_EXCL => ENOENT on attempt to link those guys

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 14 insertions, 2 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 778e253e3d48..66998b06d822 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2948,8 +2948,14 @@ static int do_tmpfile(int dfd, struct filename *pathname,
         if (error)
                 goto out2;
         error = open_check_o_direct(file);
-        if (error)
+        if (error) {
                 fput(file);
+        } else if (!(op->open_flag & O_EXCL)) {
+                struct inode *inode = file_inode(file);
+                spin_lock(&inode->i_lock);
+                inode->i_state |= I_LINKABLE;
+                spin_unlock(&inode->i_lock);
+        }
 out2:
         mnt_drop_write(nd->path.mnt);
 out:
@@ -3628,12 +3634,18 @@ int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_de
 
         mutex_lock(&inode->i_mutex);
         /* Make sure we don't allow creating hardlink to an unlinked file */
-        if (inode->i_nlink == 0)
+        if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
                 error =  -ENOENT;
         else if (max_links && inode->i_nlink >= max_links)
                 error = -EMLINK;
         else
                 error = dir->i_op->link(old_dentry, dir, new_dentry);
+
+        if (!error && (inode->i_state & I_LINKABLE)) {
+                spin_lock(&inode->i_lock);
+                inode->i_state &= ~I_LINKABLE;
+                spin_unlock(&inode->i_lock);
+        }
         mutex_unlock(&inode->i_mutex);
         if (!error)
                 fsnotify_link(dir, inode, new_dentry);