writeback: ensure that WB_SYNC_NONE writeback with sb pinned is sync

Even if the writeout itself isn't a data integrity operation, we need
to ensure that the caller doesn't drop the sb umount sem before we
have actually done the writeback.

This is a fixup for commit e913fc82.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 11 insertions, 5 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 0f629571234f..76f546d56a64 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -193,7 +193,8 @@ static void bdi_wait_on_work_clear(struct bdi_work *work)
 }
 
 static void bdi_alloc_queue_work(struct backing_dev_info *bdi,
-                                 struct wb_writeback_args *args)
+                                 struct wb_writeback_args *args,
+                                 int wait)
 {
         struct bdi_work *work;
 
@@ -205,6 +206,8 @@ static void bdi_alloc_queue_work(struct backing_dev_info *bdi,
         if (work) {
                 bdi_work_init(work, args);
                 bdi_queue_work(bdi, work);
+                if (wait)
+                        bdi_wait_on_work_clear(work);
         } else {
                 struct bdi_writeback *wb = &bdi->wb;
 
@@ -279,7 +282,7 @@ void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
                 args.for_background = 1;
         }
 
-        bdi_alloc_queue_work(bdi, &args);
+        bdi_alloc_queue_work(bdi, &args, sb_locked);
 }
 
 /*
@@ -909,6 +912,7 @@ long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
 
         while ((work = get_next_work_item(bdi, wb)) != NULL) {
                 struct wb_writeback_args args = work->args;
+                int post_clear;
 
                 /*
                  * Override sync mode, in case we must wait for completion
@@ -916,11 +920,13 @@ long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
                 if (force_wait)
                         work->args.sync_mode = args.sync_mode = WB_SYNC_ALL;
 
+                post_clear = WB_SYNC_ALL || args.sb_pinned;
+
                 /*
                  * If this isn't a data integrity operation, just notify
                  * that we have seen this work and we are now starting it.
                  */
-                if (args.sync_mode == WB_SYNC_NONE)
+                if (!post_clear)
                         wb_clear_pending(wb, work);
 
                 wrote += wb_writeback(wb, &args);
@@ -929,7 +935,7 @@ long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
                  * This is a data integrity writeback, so only do the
                  * notification when we have completed the work.
                  */
-                if (args.sync_mode == WB_SYNC_ALL)
+                if (post_clear)
                         wb_clear_pending(wb, work);
         }
 
@@ -1000,7 +1006,7 @@ static void bdi_writeback_all(struct super_block *sb, long nr_pages)
                 if (!bdi_has_dirty_io(bdi))
                         continue;
 
-                bdi_alloc_queue_work(bdi, &args);
+                bdi_alloc_queue_work(bdi, &args, 0);
         }
 
         rcu_read_unlock();