Btrfs: Use async helpers to deal with pages that have been improperly dirtied

Higher layers sometimes call set_page_dirty without asking the filesystem
to help.  This causes many problems for the data=ordered and cow code.
This commit detects pages that haven't been properly setup for IO and
kicks off an async helper to deal with them.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index ceebc052ddcb..4ddc8a8f82cd 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -546,6 +546,12 @@ struct btrfs_fs_info {
         struct btrfs_workers endio_workers;
         struct btrfs_workers endio_write_workers;
         struct btrfs_workers submit_workers;
+        /*
+         * fixup workers take dirty pages that didn't properly go through
+         * the cow mechanism and make them safe to write.  It happens
+         * for the sys_munmap function call path
+         */
+        struct btrfs_workers fixup_workers;
         struct task_struct *transaction_kthread;
         struct task_struct *cleaner_kthread;
         int thread_pool_size;