Merge branch 'for-linus' of git://git.kernel.dk/linux-2.6-block

* 'for-linus' of git://git.kernel.dk/linux-2.6-block: (28 commits)
  cfq-iosched: add close cooperator code
  cfq-iosched: log responsible 'cfqq' in idle timer arm
  cfq-iosched: tweak kick logic a bit more
  cfq-iosched: no need to save interrupts in cfq_kick_queue()
  brd: fix cacheflushing
  brd: support barriers
  swap: Remove code handling bio_alloc failure with __GFP_WAIT
  gfs2: Remove code handling bio_alloc failure with __GFP_WAIT
  ext4: Remove code handling bio_alloc failure with __GFP_WAIT
  dio: Remove code handling bio_alloc failure with __GFP_WAIT
  block: Remove code handling bio_alloc failure with __GFP_WAIT
  bio: add documentation to bio_alloc()
  splice: add helpers for locking pipe inode
  splice: remove generic_file_splice_write_nolock()
  ocfs2: fix i_mutex locking in ocfs2_splice_to_file()
  splice: fix i_mutex locking in generic_splice_write()
  splice: remove i_mutex locking in splice_from_pipe()
  splice: split up __splice_from_pipe()
  block: fix SG_IO to return a proper error value
  cfq-iosched: don't delay queue kick for a merged request
  ...

1 files changed, 38 insertions, 4 deletions

diff --git a/fs/pipe.c b/fs/pipe.c
index 4af7aa521813..13414ec45b8d 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -37,6 +37,42 @@
  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  */
 
+static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
+{
+        if (pipe->inode)
+                mutex_lock_nested(&pipe->inode->i_mutex, subclass);
+}
+
+void pipe_lock(struct pipe_inode_info *pipe)
+{
+        /*
+         * pipe_lock() nests non-pipe inode locks (for writing to a file)
+         */
+        pipe_lock_nested(pipe, I_MUTEX_PARENT);
+}
+EXPORT_SYMBOL(pipe_lock);
+
+void pipe_unlock(struct pipe_inode_info *pipe)
+{
+        if (pipe->inode)
+                mutex_unlock(&pipe->inode->i_mutex);
+}
+EXPORT_SYMBOL(pipe_unlock);
+
+void pipe_double_lock(struct pipe_inode_info *pipe1,
+                      struct pipe_inode_info *pipe2)
+{
+        BUG_ON(pipe1 == pipe2);
+
+        if (pipe1 < pipe2) {
+                pipe_lock_nested(pipe1, I_MUTEX_PARENT);
+                pipe_lock_nested(pipe2, I_MUTEX_CHILD);
+        } else {
+                pipe_lock_nested(pipe2, I_MUTEX_CHILD);
+                pipe_lock_nested(pipe1, I_MUTEX_PARENT);
+        }
+}
+
 /* Drop the inode semaphore and wait for a pipe event, atomically */
 void pipe_wait(struct pipe_inode_info *pipe)
 {
@@ -47,12 +83,10 @@ void pipe_wait(struct pipe_inode_info *pipe)
          * is considered a noninteractive wait:
          */
         prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
-        if (pipe->inode)
-                mutex_unlock(&pipe->inode->i_mutex);
+        pipe_unlock(pipe);
         schedule();
         finish_wait(&pipe->wait, &wait);
-        if (pipe->inode)
-                mutex_lock(&pipe->inode->i_mutex);
+        pipe_lock(pipe);
 }
 
 static int