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, 10 insertions, 0 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 3f82a6e9ca4f..feff16cb9b40 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2050,6 +2050,16 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
         lock_extent(tree, start, page_end, GFP_NOFS);
         unlock_start = start;
 
+        if (tree->ops && tree->ops->writepage_start_hook) {
+                ret = tree->ops->writepage_start_hook(page, start, page_end);
+                if (ret == -EAGAIN) {
+                        unlock_extent(tree, start, page_end, GFP_NOFS);
+                        redirty_page_for_writepage(wbc, page);
+                        unlock_page(page);
+                        return 0;
+                }
+        }
+
         end = page_end;
         if (test_range_bit(tree, start, page_end, EXTENT_DELALLOC, 0)) {
                 printk("found delalloc bits after lock_extent\n");