1 files changed, 24 insertions, 0 deletions

diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
index 05eca817d704..b79ad5126468 100644
--- a/fs/ext4/ext4_jbd2.h
+++ b/fs/ext4/ext4_jbd2.h
@@ -304,4 +304,28 @@ static inline int ext4_should_writeback_data(struct inode *inode)
         return 0;
 }
 
+/*
+ * This function controls whether or not we should try to go down the
+ * dioread_nolock code paths, which makes it safe to avoid taking
+ * i_mutex for direct I/O reads.  This only works for extent-based
+ * files, and it doesn't work for nobh or if data journaling is
+ * enabled, since the dioread_nolock code uses b_private to pass
+ * information back to the I/O completion handler, and this conflicts
+ * with the jbd's use of b_private.
+ */
+static inline int ext4_should_dioread_nolock(struct inode *inode)
+{
+        if (!test_opt(inode->i_sb, DIOREAD_NOLOCK))
+                return 0;
+        if (test_opt(inode->i_sb, NOBH))
+                return 0;
+        if (!S_ISREG(inode->i_mode))
+                return 0;
+        if (!(EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL))
+                return 0;
+        if (ext4_should_journal_data(inode))
+                return 0;
+        return 1;
+}
+
 #endif  /* _EXT4_JBD2_H */