VFS: Make more complete truncate operation available to CacheFiles

Make a more complete truncate operation available to CacheFiles (including
security checks and suchlike) so that it can use this to clear invalidated
cache files.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 27 insertions, 23 deletions

diff --git a/fs/open.c b/fs/open.c
index 182d8667b7bd..c819bbdab47f 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -61,33 +61,22 @@ int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
         return ret;
 }
 
-static long do_sys_truncate(const char __user *pathname, loff_t length)
+long vfs_truncate(struct path *path, loff_t length)
 {
-        struct path path;
         struct inode *inode;
-        int error;
-
-        error = -EINVAL;
-        if (length < 0) /* sorry, but loff_t says... */
-                goto out;
+        long error;
 
-        error = user_path(pathname, &path);
-        if (error)
-                goto out;
-        inode = path.dentry->d_inode;
+        inode = path->dentry->d_inode;
 
         /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
-        error = -EISDIR;
         if (S_ISDIR(inode->i_mode))
-                goto dput_and_out;
-
-        error = -EINVAL;
+                return -EISDIR;
         if (!S_ISREG(inode->i_mode))
-                goto dput_and_out;
+                return -EINVAL;
 
-        error = mnt_want_write(path.mnt);
+        error = mnt_want_write(path->mnt);
         if (error)
-                goto dput_and_out;
+                goto out;
 
         error = inode_permission(inode, MAY_WRITE);
         if (error)
@@ -111,19 +100,34 @@ static long do_sys_truncate(const char __user *pathname, loff_t length)
 
         error = locks_verify_truncate(inode, NULL, length);
         if (!error)
-                error = security_path_truncate(&path);
+                error = security_path_truncate(path);
         if (!error)
-                error = do_truncate(path.dentry, length, 0, NULL);
+                error = do_truncate(path->dentry, length, 0, NULL);
 
 put_write_and_out:
         put_write_access(inode);
 mnt_drop_write_and_out:
-        mnt_drop_write(path.mnt);
-dput_and_out:
-        path_put(&path);
+        mnt_drop_write(path->mnt);
 out:
         return error;
 }
+EXPORT_SYMBOL_GPL(vfs_truncate);
+
+static long do_sys_truncate(const char __user *pathname, loff_t length)
+{
+        struct path path;
+        int error;
+
+        if (length < 0) /* sorry, but loff_t says... */
+                return -EINVAL;
+
+        error = user_path(pathname, &path);
+        if (!error) {
+                error = vfs_truncate(&path, length);
+                path_put(&path);
+        }
+        return error;
+}
 
 SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
 {