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>

1 files changed, 4 insertions, 4 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);