Merge tag 'ext4_for_linus_bugfixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4

Pull ext4 fixes from Ted Ts'o:
 "Two ext4 bug fixes, one being a revert of a commit sent during the
  merge window"

* tag 'ext4_for_linus_bugfixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
  Revert "ext4: fix superblock checksum calculation race"
  ext4: handle dax mount option collision

fs/ext4/ext4.h

@@ -1231,13 +1231,13 @@ struct ext4_inode_info {
 						      blocks */
 #define EXT4_MOUNT2_HURD_COMPAT		0x00000004 /* Support HURD-castrated
 						      file systems */
-#define EXT4_MOUNT2_DAX_NEVER		0x00000008 /* Do not allow Direct Access */
-#define EXT4_MOUNT2_DAX_INODE		0x00000010 /* For printing options only */
-
 #define EXT4_MOUNT2_EXPLICIT_JOURNAL_CHECKSUM	0x00000008 /* User explicitly
 						specified journal checksum */
 
 #define EXT4_MOUNT2_JOURNAL_FAST_COMMIT	0x00000010 /* Journal fast commit */
+#define EXT4_MOUNT2_DAX_NEVER		0x00000020 /* Do not allow Direct Access */
+#define EXT4_MOUNT2_DAX_INODE		0x00000040 /* For printing options only */
+
 
 #define clear_opt(sb, opt)		EXT4_SB(sb)->s_mount_opt &= \
 						~EXT4_MOUNT_##opt

fs/ext4/super.c

@@ -289,18 +289,7 @@ void ext4_superblock_csum_set(struct super_block *sb)
 	if (!ext4_has_metadata_csum(sb))
 		return;
 
-	/*
-	 * Locking the superblock prevents the scenario
-	 * where:
-	 *  1) a first thread pauses during checksum calculation.
-	 *  2) a second thread updates the superblock, recalculates
-	 *     the checksum, and updates s_checksum
-	 *  3) the first thread resumes and finishes its checksum calculation
-	 *     and updates s_checksum with a potentially stale or torn value.
-	 */
-	lock_buffer(EXT4_SB(sb)->s_sbh);
 	es->s_checksum = ext4_superblock_csum(sb, es);
-	unlock_buffer(EXT4_SB(sb)->s_sbh);
 }
 
 ext4_fsblk_t ext4_block_bitmap(struct super_block *sb,