locks: break delegations on any attribute modification
NFSv4 uses leases to guarantee that clients can cache metadata as well
as data.
Cc: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Cc: David Howells <dhowells@redhat.com>
Cc: Tyler Hicks <tyhicks@canonical.com>
Cc: Dustin Kirkland <dustin.kirkland@gazzang.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/attr.c b/fs/attr.c
index 1449adb..267968d 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -167,7 +167,27 @@
}
EXPORT_SYMBOL(setattr_copy);
-int notify_change(struct dentry * dentry, struct iattr * attr)
+/**
+ * notify_change - modify attributes of a filesytem object
+ * @dentry: object affected
+ * @iattr: new attributes
+ * @delegated_inode: returns inode, if the inode is delegated
+ *
+ * The caller must hold the i_mutex on the affected object.
+ *
+ * If notify_change discovers a delegation in need of breaking,
+ * it will return -EWOULDBLOCK and return a reference to the inode in
+ * delegated_inode. The caller should then break the delegation and
+ * retry. Because breaking a delegation may take a long time, the
+ * caller should drop the i_mutex before doing so.
+ *
+ * Alternatively, a caller may pass NULL for delegated_inode. This may
+ * be appropriate for callers that expect the underlying filesystem not
+ * to be NFS exported. Also, passing NULL is fine for callers holding
+ * the file open for write, as there can be no conflicting delegation in
+ * that case.
+ */
+int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode)
{
struct inode *inode = dentry->d_inode;
umode_t mode = inode->i_mode;
@@ -243,6 +263,9 @@
error = security_inode_setattr(dentry, attr);
if (error)
return error;
+ error = try_break_deleg(inode, delegated_inode);
+ if (error)
+ return error;
if (inode->i_op->setattr)
error = inode->i_op->setattr(dentry, attr);