Merge tag 'ext4_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4

Pull ext4 update from Ted Ts'o:
 "Fixed regressions (two stability regressions and a performance
  regression) introduced during the 3.10-rc1 merge window.

  Also included is a bug fix relating to allocating blocks after
  resizing an ext3 file system when using the ext4 file system driver"

* tag 'ext4_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
  jbd,jbd2: fix oops in jbd2_journal_put_journal_head()
  ext4: revert "ext4: use io_end for multiple bios"
  ext4: limit group search loop for non-extent files
  ext4: fix fio regression

1 files changed, 6 insertions, 2 deletions

diff --git a/include/linux/journal-head.h b/include/linux/journal-head.h
index 13a3da25ff07..98cd41bb39c8 100644
--- a/include/linux/journal-head.h
+++ b/include/linux/journal-head.h
@@ -30,15 +30,19 @@ struct journal_head {
 
         /*
          * Journalling list for this buffer [jbd_lock_bh_state()]
+         * NOTE: We *cannot* combine this with b_modified into a bitfield
+         * as gcc would then (which the C standard allows but which is
+         * very unuseful) make 64-bit accesses to the bitfield and clobber
+         * b_jcount if its update races with bitfield modification.
          */
-        unsigned b_jlist:4;
+        unsigned b_jlist;
 
         /*
          * This flag signals the buffer has been modified by
          * the currently running transaction
          * [jbd_lock_bh_state()]
          */
-        unsigned b_modified:1;
+        unsigned b_modified;
 
         /*
          * Copy of the buffer data frozen for writing to the log.