fs: move i_wb_list out from under inode_lock

Protect the inode writeback list with a new global lock
inode_wb_list_lock and use it to protect the list manipulations and
traversals. This lock replaces the inode_lock as the inodes on the
list can be validity checked while holding the inode->i_lock and
hence the inode_lock is no longer needed to protect the list.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

3 files changed, 10 insertions, 10 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 027100d30227..4b3e9f17ee21 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -73,14 +73,14 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
         struct inode *inode;
 
         nr_wb = nr_dirty = nr_io = nr_more_io = 0;
-        spin_lock(&inode_lock);
+        spin_lock(&inode_wb_list_lock);
         list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
                 nr_dirty++;
         list_for_each_entry(inode, &wb->b_io, i_wb_list)
                 nr_io++;
         list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
                 nr_more_io++;
-        spin_unlock(&inode_lock);
+        spin_unlock(&inode_wb_list_lock);
 
         global_dirty_limits(&background_thresh, &dirty_thresh);
         bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
@@ -682,11 +682,11 @@ void bdi_destroy(struct backing_dev_info *bdi)
         if (bdi_has_dirty_io(bdi)) {
                 struct bdi_writeback *dst = &default_backing_dev_info.wb;
 
-                spin_lock(&inode_lock);
+                spin_lock(&inode_wb_list_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);
+                spin_unlock(&inode_wb_list_lock);
         }
 
         bdi_unregister(bdi);
diff --git a/mm/filemap.c b/mm/filemap.c
index 499e9aa91450..d8b34d1a1071 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -80,8 +80,8 @@
  *  ->i_mutex
  *    ->i_alloc_sem             (various)
  *
- *  ->inode_lock
- *    ->sb_lock                 (fs/fs-writeback.c)
+ *  inode_wb_list_lock
+ *    sb_lock                   (fs/fs-writeback.c)
  *    ->mapping->tree_lock      (__sync_single_inode)
  *
  *  ->i_mmap_lock
@@ -98,9 +98,9 @@
  *    ->zone.lru_lock           (check_pte_range->isolate_lru_page)
  *    ->private_lock            (page_remove_rmap->set_page_dirty)
  *    ->tree_lock               (page_remove_rmap->set_page_dirty)
- *    ->inode_lock              (page_remove_rmap->set_page_dirty)
+ *    inode_wb_list_lock        (page_remove_rmap->set_page_dirty)
  *    ->inode->i_lock           (page_remove_rmap->set_page_dirty)
- *    ->inode_lock              (zap_pte_range->set_page_dirty)
+ *    inode_wb_list_lock        (zap_pte_range->set_page_dirty)
  *    ->inode->i_lock           (zap_pte_range->set_page_dirty)
  *    ->private_lock            (zap_pte_range->__set_page_dirty_buffers)
  *
diff --git a/mm/rmap.c b/mm/rmap.c
index 7dada0456448..8da044a1db0f 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -31,12 +31,12 @@
  *             swap_lock (in swap_duplicate, swap_info_get)
  *               mmlist_lock (in mmput, drain_mmlist and others)
  *               mapping->private_lock (in __set_page_dirty_buffers)
- *               inode_lock (in set_page_dirty's __mark_inode_dirty)
  *               inode->i_lock (in set_page_dirty's __mark_inode_dirty)
+ *               inode_wb_list_lock (in set_page_dirty's __mark_inode_dirty)
  *                 sb_lock (within inode_lock in fs/fs-writeback.c)
  *                 mapping->tree_lock (widely used, in set_page_dirty,
  *                           in arch-dependent flush_dcache_mmap_lock,
- *                           within inode_lock in __sync_single_inode)
+ *                           within inode_wb_list_lock in __sync_single_inode)
  *
  * (code doesn't rely on that order so it could be switched around)
  * ->tasklist_lock