1 files changed, 24 insertions, 13 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 3ebccf4aa7e3..39ff14403d13 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -627,8 +627,7 @@ repeat:
 }
 
 /**
- * sync_mapping_buffers - write out and wait upon a mapping's "associated"
- *                        buffers
+ * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
  * @mapping: the mapping which wants those buffers written
  *
  * Starts I/O against the buffers at mapping->private_list, and waits upon
@@ -836,7 +835,7 @@ static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
                 smp_mb();
                 if (buffer_dirty(bh)) {
                         list_add(&bh->b_assoc_buffers,
-                                 &bh->b_assoc_map->private_list);
+                                 &mapping->private_list);
                         bh->b_assoc_map = mapping;
                 }
                 spin_unlock(lock);
@@ -1182,7 +1181,20 @@ __getblk_slow(struct block_device *bdev, sector_t block, int size)
 void mark_buffer_dirty(struct buffer_head *bh)
 {
         WARN_ON_ONCE(!buffer_uptodate(bh));
-        if (!buffer_dirty(bh) && !test_set_buffer_dirty(bh))
+
+        /*
+         * Very *carefully* optimize the it-is-already-dirty case.
+         *
+         * Don't let the final "is it dirty" escape to before we
+         * perhaps modified the buffer.
+         */
+        if (buffer_dirty(bh)) {
+                smp_mb();
+                if (buffer_dirty(bh))
+                        return;
+        }
+
+        if (!test_set_buffer_dirty(bh))
                 __set_page_dirty(bh->b_page, page_mapping(bh->b_page), 0);
 }
 
@@ -2565,14 +2577,13 @@ int nobh_write_end(struct file *file, struct address_space *mapping,
         struct inode *inode = page->mapping->host;
         struct buffer_head *head = fsdata;
         struct buffer_head *bh;
+        BUG_ON(fsdata != NULL && page_has_buffers(page));
 
-        if (!PageMappedToDisk(page)) {
-                if (unlikely(copied < len) && !page_has_buffers(page))
-                        attach_nobh_buffers(page, head);
-                if (page_has_buffers(page))
-                        return generic_write_end(file, mapping, pos, len,
-                                                copied, page, fsdata);
-        }
+        if (unlikely(copied < len) && !page_has_buffers(page))
+                attach_nobh_buffers(page, head);
+        if (page_has_buffers(page))
+                return generic_write_end(file, mapping, pos, len,
+                                        copied, page, fsdata);
 
         SetPageUptodate(page);
         set_page_dirty(page);
@@ -3214,7 +3225,7 @@ static int buffer_cpu_notify(struct notifier_block *self,
 }
 
 /**
- * bh_uptodate_or_lock: Test whether the buffer is uptodate
+ * bh_uptodate_or_lock - Test whether the buffer is uptodate
  * @bh: struct buffer_head
  *
  * Return true if the buffer is up-to-date and false,
@@ -3233,7 +3244,7 @@ int bh_uptodate_or_lock(struct buffer_head *bh)
 EXPORT_SYMBOL(bh_uptodate_or_lock);
 
 /**
- * bh_submit_read: Submit a locked buffer for reading
+ * bh_submit_read - Submit a locked buffer for reading
  * @bh: struct buffer_head
  *
  * Returns zero on success and -EIO on error.