On 5/5/11 7:10 AM, Jan Kara wrote: > In do_get_write_access() we wait on BH_Unshadow bit for buffer to get > from shadow state. The waking code in journal_commit_transaction() has > a bug because it does not issue a memory barrier after the buffer is moved > from the shadow state and before wake_up_bit() is called. Thus a waitqueue > check can happen before the buffer is actually moved from the shadow state > and waiting process may never be woken. Fix the problem by issuing proper > barrier. needed for jbd/commit.c as well, I guess? -Eric > Reported-by: Tao Ma <boyu.mt@xxxxxxxxxx> > Signed-off-by: Jan Kara <jack@xxxxxxx> > --- > fs/jbd2/commit.c | 9 +++++++-- > 1 files changed, 7 insertions(+), 2 deletions(-) > > Analogous JBD fix has been queued in my tree... > > diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c > index 2e5d370..3a958c7 100644 > --- a/fs/jbd2/commit.c > +++ b/fs/jbd2/commit.c > @@ -768,8 +768,13 @@ wait_for_iobuf: > required. */ > JBUFFER_TRACE(jh, "file as BJ_Forget"); > jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget); > - /* Wake up any transactions which were waiting for this > - IO to complete */ > + /* > + * Wake up any transactions which were waiting for this IO to > + * complete. The barrier must be here so that changes by > + * jbd2_journal_file_buffer() take effect before wake_up_bit() > + * does the waitqueue check. > + */ > + smp_mb(); > wake_up_bit(&bh->b_state, BH_Unshadow); > JBUFFER_TRACE(jh, "brelse shadowed buffer"); > __brelse(bh); -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
