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>

diff --git a/fs/inode.c b/fs/inode.c
index 00d5fc3b86e12419d2d350032b173009bddcd2cd..d6dfb09c828083b8ba64d3e8aacb2b6a64581038 100644 (file)
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -333,8 +333,10 @@ EXPORT_SYMBOL(set_nlink);
  */
 void inc_nlink(struct inode *inode)
 {
-       if (WARN_ON(inode->i_nlink == 0))
+       if (unlikely(inode->i_nlink == 0)) {
+               WARN_ON(!(inode->i_state & I_LINKABLE));
                atomic_long_dec(&inode->i_sb->s_remove_count);
+       }
 
        inode->__i_nlink++;
 }

diff --git a/fs/namei.c b/fs/namei.c
index 778e253e3d4850916a07bb7d3856a888471c0424..66998b06d82234117b1778199788f8d869f81028 100644 (file)
--- 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);

diff --git a/include/linux/fs.h b/include/linux/fs.h
index dd6615f0fd13a8a0e934f7b5c86399f94fe19c0a..ab11c44b069766aa2646cad7ffc16a0d94345857 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1744,6 +1744,7 @@ struct super_operations {
 #define I_REFERENCED           (1 << 8)
 #define __I_DIO_WAKEUP         9
 #define I_DIO_WAKEUP           (1 << I_DIO_WAKEUP)
+#define I_LINKABLE             (1 << 10)
 
 #define I_DIRTY (I_DIRTY_SYNC | I_DIRTY_DATASYNC | I_DIRTY_PAGES)