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

* 'writeback' of git://git.kernel.dk/linux-2.6-block:
  writeback: fix possible bdi writeback refcounting problem
  writeback: Fix bdi use after free in wb_work_complete()
  writeback: improve scalability of bdi writeback work queues
  writeback: remove smp_mb(), it's not needed with list_add_tail_rcu()
  writeback: use schedule_timeout_interruptible()
  writeback: add comments to bdi_work structure
  writeback: splice dirty inode entries to default bdi on bdi_destroy()
  writeback: separate starting of sync vs opportunistic writeback
  writeback: inline allocation failure handling in bdi_alloc_queue_work()
  writeback: use RCU to protect bdi_list
  writeback: only use bdi_writeback_all() for WB_SYNC_NONE writeout
  fs: Assign bdi in super_block
  writeback: make wb_writeback() take an argument structure
  writeback: merely wakeup flusher thread if work allocation fails for WB_SYNC_NONE
  writeback: get rid of wbc->for_writepages
  fs: remove bdev->bd_inode_backing_dev_info

2 files changed, 74 insertions, 38 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index d3ca0dac1111..3d3accb1f800 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -26,6 +26,12 @@ struct backing_dev_info default_backing_dev_info = {
 EXPORT_SYMBOL_GPL(default_backing_dev_info);
 
 static struct class *bdi_class;
+
+/*
+ * bdi_lock protects updates to bdi_list and bdi_pending_list, as well as
+ * reader side protection for bdi_pending_list. bdi_list has RCU reader side
+ * locking.
+ */
 DEFINE_SPINLOCK(bdi_lock);
 LIST_HEAD(bdi_list);
 LIST_HEAD(bdi_pending_list);
@@ -284,9 +290,9 @@ static int bdi_start_fn(void *ptr)
         /*
          * Add us to the active bdi_list
          */
-        spin_lock(&bdi_lock);
-        list_add(&bdi->bdi_list, &bdi_list);
-        spin_unlock(&bdi_lock);
+        spin_lock_bh(&bdi_lock);
+        list_add_rcu(&bdi->bdi_list, &bdi_list);
+        spin_unlock_bh(&bdi_lock);
 
         bdi_task_init(bdi, wb);
 
@@ -389,7 +395,7 @@ static int bdi_forker_task(void *ptr)
                 if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list))
                         wb_do_writeback(me, 0);
 
-                spin_lock(&bdi_lock);
+                spin_lock_bh(&bdi_lock);
 
                 /*
                  * Check if any existing bdi's have dirty data without
@@ -410,7 +416,7 @@ static int bdi_forker_task(void *ptr)
                 if (list_empty(&bdi_pending_list)) {
                         unsigned long wait;
 
-                        spin_unlock(&bdi_lock);
+                        spin_unlock_bh(&bdi_lock);
                         wait = msecs_to_jiffies(dirty_writeback_interval * 10);
                         schedule_timeout(wait);
                         try_to_freeze();
@@ -426,7 +432,7 @@ static int bdi_forker_task(void *ptr)
                 bdi = list_entry(bdi_pending_list.next, struct backing_dev_info,
                                  bdi_list);
                 list_del_init(&bdi->bdi_list);
-                spin_unlock(&bdi_lock);
+                spin_unlock_bh(&bdi_lock);
 
                 wb = &bdi->wb;
                 wb->task = kthread_run(bdi_start_fn, wb, "flush-%s",
@@ -445,9 +451,9 @@ static int bdi_forker_task(void *ptr)
                          * a chance to flush other bdi's to free
                          * memory.
                          */
-                        spin_lock(&bdi_lock);
+                        spin_lock_bh(&bdi_lock);
                         list_add_tail(&bdi->bdi_list, &bdi_pending_list);
-                        spin_unlock(&bdi_lock);
+                        spin_unlock_bh(&bdi_lock);
 
                         bdi_flush_io(bdi);
                 }
@@ -456,6 +462,24 @@ static int bdi_forker_task(void *ptr)
         return 0;
 }
 
+static void bdi_add_to_pending(struct rcu_head *head)
+{
+        struct backing_dev_info *bdi;
+
+        bdi = container_of(head, struct backing_dev_info, rcu_head);
+        INIT_LIST_HEAD(&bdi->bdi_list);
+
+        spin_lock(&bdi_lock);
+        list_add_tail(&bdi->bdi_list, &bdi_pending_list);
+        spin_unlock(&bdi_lock);
+
+        /*
+         * We are now on the pending list, wake up bdi_forker_task()
+         * to finish the job and add us back to the active bdi_list
+         */
+        wake_up_process(default_backing_dev_info.wb.task);
+}
+
 /*
  * Add the default flusher task that gets created for any bdi
  * that has dirty data pending writeout
@@ -478,16 +502,29 @@ void static bdi_add_default_flusher_task(struct backing_dev_info *bdi)
          * waiting for previous additions to finish.
          */
         if (!test_and_set_bit(BDI_pending, &bdi->state)) {
-                list_move_tail(&bdi->bdi_list, &bdi_pending_list);
+                list_del_rcu(&bdi->bdi_list);
 
                 /*
-                 * We are now on the pending list, wake up bdi_forker_task()
-                 * to finish the job and add us back to the active bdi_list
+                 * We must wait for the current RCU period to end before
+                 * moving to the pending list. So schedule that operation
+                 * from an RCU callback.
                  */
-                wake_up_process(default_backing_dev_info.wb.task);
+                call_rcu(&bdi->rcu_head, bdi_add_to_pending);
         }
 }
 
+/*
+ * Remove bdi from bdi_list, and ensure that it is no longer visible
+ */
+static void bdi_remove_from_list(struct backing_dev_info *bdi)
+{
+        spin_lock_bh(&bdi_lock);
+        list_del_rcu(&bdi->bdi_list);
+        spin_unlock_bh(&bdi_lock);
+
+        synchronize_rcu();
+}
+
 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
                 const char *fmt, ...)
 {
@@ -506,9 +543,9 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
                 goto exit;
         }
 
-        spin_lock(&bdi_lock);
-        list_add_tail(&bdi->bdi_list, &bdi_list);
-        spin_unlock(&bdi_lock);
+        spin_lock_bh(&bdi_lock);
+        list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
+        spin_unlock_bh(&bdi_lock);
 
         bdi->dev = dev;
 
@@ -526,9 +563,7 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
                         wb->task = NULL;
                         ret = -ENOMEM;
 
-                        spin_lock(&bdi_lock);
-                        list_del(&bdi->bdi_list);
-                        spin_unlock(&bdi_lock);
+                        bdi_remove_from_list(bdi);
                         goto exit;
                 }
         }
@@ -565,9 +600,7 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi)
         /*
          * Make sure nobody finds us on the bdi_list anymore
          */
-        spin_lock(&bdi_lock);
-        list_del(&bdi->bdi_list);
-        spin_unlock(&bdi_lock);
+        bdi_remove_from_list(bdi);
 
         /*
          * Finally, kill the kernel threads. We don't need to be RCU
@@ -599,6 +632,7 @@ int bdi_init(struct backing_dev_info *bdi)
         bdi->max_ratio = 100;
         bdi->max_prop_frac = PROP_FRAC_BASE;
         spin_lock_init(&bdi->wb_lock);
+        INIT_RCU_HEAD(&bdi->rcu_head);
         INIT_LIST_HEAD(&bdi->bdi_list);
         INIT_LIST_HEAD(&bdi->wb_list);
         INIT_LIST_HEAD(&bdi->work_list);
@@ -634,7 +668,19 @@ void bdi_destroy(struct backing_dev_info *bdi)
 {
         int i;
 
-        WARN_ON(bdi_has_dirty_io(bdi));
+        /*
+         * Splice our entries to the default_backing_dev_info, if this
+         * bdi disappears
+         */
+        if (bdi_has_dirty_io(bdi)) {
+                struct bdi_writeback *dst = &default_backing_dev_info.wb;
+
+                spin_lock(&inode_lock);
+                list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
+                list_splice(&bdi->wb.b_io, &dst->b_io);
+                list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
+                spin_unlock(&inode_lock);
+        }
 
         bdi_unregister(bdi);
 
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index dd73d29c15a8..1eea4fa0d410 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -315,7 +315,7 @@ int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
 {
         int ret = 0;
 
-        spin_lock(&bdi_lock);
+        spin_lock_bh(&bdi_lock);
         if (min_ratio > bdi->max_ratio) {
                 ret = -EINVAL;
         } else {
@@ -327,7 +327,7 @@ int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
                         ret = -EINVAL;
                 }
         }
-        spin_unlock(&bdi_lock);
+        spin_unlock_bh(&bdi_lock);
 
         return ret;
 }
@@ -339,14 +339,14 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio)
         if (max_ratio > 100)
                 return -EINVAL;
 
-        spin_lock(&bdi_lock);
+        spin_lock_bh(&bdi_lock);
         if (bdi->min_ratio > max_ratio) {
                 ret = -EINVAL;
         } else {
                 bdi->max_ratio = max_ratio;
                 bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100;
         }
-        spin_unlock(&bdi_lock);
+        spin_unlock_bh(&bdi_lock);
 
         return ret;
 }
@@ -582,16 +582,8 @@ static void balance_dirty_pages(struct address_space *mapping)
         if ((laptop_mode && pages_written) ||
             (!laptop_mode && ((nr_writeback = global_page_state(NR_FILE_DIRTY)
                                           + global_page_state(NR_UNSTABLE_NFS))
-                                          > background_thresh))) {
-                struct writeback_control wbc = {
-                        .bdi            = bdi,
-                        .sync_mode      = WB_SYNC_NONE,
-                        .nr_to_write    = nr_writeback,
-                };
-
-
-                bdi_start_writeback(&wbc);
-        }
+                                          > background_thresh)))
+                bdi_start_writeback(bdi, nr_writeback);
 }
 
 void set_page_dirty_balance(struct page *page, int page_mkwrite)
@@ -1020,12 +1012,10 @@ int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
 
         if (wbc->nr_to_write <= 0)
                 return 0;
-        wbc->for_writepages = 1;
         if (mapping->a_ops->writepages)
                 ret = mapping->a_ops->writepages(mapping, wbc);
         else
                 ret = generic_writepages(mapping, wbc);
-        wbc->for_writepages = 0;
         return ret;
 }