1 files changed, 47 insertions, 0 deletions

diff --git a/fs/inode.c b/fs/inode.c
index f0335fc315ed..c99163b1b310 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1836,3 +1836,50 @@ bool inode_owner_or_capable(const struct inode *inode)
         return false;
 }
 EXPORT_SYMBOL(inode_owner_or_capable);
+
+/*
+ * Direct i/o helper functions
+ */
+static void __inode_dio_wait(struct inode *inode)
+{
+        wait_queue_head_t *wq = bit_waitqueue(&inode->i_state, __I_DIO_WAKEUP);
+        DEFINE_WAIT_BIT(q, &inode->i_state, __I_DIO_WAKEUP);
+
+        do {
+                prepare_to_wait(wq, &q.wait, TASK_UNINTERRUPTIBLE);
+                if (atomic_read(&inode->i_dio_count))
+                        schedule();
+        } while (atomic_read(&inode->i_dio_count));
+        finish_wait(wq, &q.wait);
+}
+
+/**
+ * inode_dio_wait - wait for outstanding DIO requests to finish
+ * @inode: inode to wait for
+ *
+ * Waits for all pending direct I/O requests to finish so that we can
+ * proceed with a truncate or equivalent operation.
+ *
+ * Must be called under a lock that serializes taking new references
+ * to i_dio_count, usually by inode->i_mutex.
+ */
+void inode_dio_wait(struct inode *inode)
+{
+        if (atomic_read(&inode->i_dio_count))
+                __inode_dio_wait(inode);
+}
+EXPORT_SYMBOL(inode_dio_wait);
+
+/*
+ * inode_dio_done - signal finish of a direct I/O requests
+ * @inode: inode the direct I/O happens on
+ *
+ * This is called once we've finished processing a direct I/O request,
+ * and is used to wake up callers waiting for direct I/O to be quiesced.
+ */
+void inode_dio_done(struct inode *inode)
+{
+        if (atomic_dec_and_test(&inode->i_dio_count))
+                wake_up_bit(&inode->i_state, __I_DIO_WAKEUP);
+}
+EXPORT_SYMBOL(inode_dio_done);