writeback: only use bdi_writeback_all() for WB_SYNC_NONE writeout

Data integrity writeback must use bdi_start_writeback() and ensure
that wbc->sb and wbc->bdi are set.

Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 14 insertions, 56 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index c5e91225501d..14f06b459197 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -50,7 +50,6 @@ struct wb_writeback_args {
  */
 struct bdi_work {
         struct list_head list;
-        struct list_head wait_list;
         struct rcu_head rcu_head;
 
         unsigned long seen;
@@ -198,7 +197,8 @@ static void bdi_wait_on_work_clear(struct bdi_work *work)
                     TASK_UNINTERRUPTIBLE);
 }
 
-static struct bdi_work *bdi_alloc_work(struct writeback_control *wbc)
+static void bdi_alloc_queue_work(struct backing_dev_info *bdi,
+                                 struct writeback_control *wbc)
 {
         struct bdi_work *work;
 
@@ -206,7 +206,7 @@ static struct bdi_work *bdi_alloc_work(struct writeback_control *wbc)
         if (work)
                 bdi_work_init(work, wbc);
 
-        return work;
+        bdi_queue_work(bdi, work);
 }
 
 void bdi_start_writeback(struct writeback_control *wbc)
@@ -216,11 +216,9 @@ void bdi_start_writeback(struct writeback_control *wbc)
          * bdi_queue_work() will wake up the thread and flush old data. This
          * should ensure some amount of progress in freeing memory.
          */
-        if (wbc->sync_mode != WB_SYNC_ALL) {
-                struct bdi_work *w = bdi_alloc_work(wbc);
-
-                bdi_queue_work(wbc->bdi, w);
-        } else {
+        if (wbc->sync_mode != WB_SYNC_ALL)
+                bdi_alloc_queue_work(wbc->bdi, wbc);
+        else {
                 struct bdi_work work;
 
                 bdi_work_init(&work, wbc);
@@ -860,67 +858,26 @@ int bdi_writeback_task(struct bdi_writeback *wb)
 }
 
 /*
- * Schedule writeback for all backing devices. Expensive! If this is a data
- * integrity operation, writeback will be complete when this returns. If
- * we are simply called for WB_SYNC_NONE, then writeback will merely be
- * scheduled to run.
+ * Schedule writeback for all backing devices. Can only be used for
+ * WB_SYNC_NONE writeback, WB_SYNC_ALL should use bdi_start_writeback()
+ * and pass in the superblock.
  */
 static void bdi_writeback_all(struct writeback_control *wbc)
 {
-        const bool must_wait = wbc->sync_mode == WB_SYNC_ALL;
         struct backing_dev_info *bdi;
-        struct bdi_work *work;
-        LIST_HEAD(list);
 
-restart:
+        WARN_ON(wbc->sync_mode == WB_SYNC_ALL);
+
         spin_lock(&bdi_lock);
 
         list_for_each_entry(bdi, &bdi_list, bdi_list) {
-                struct bdi_work *work;
-
                 if (!bdi_has_dirty_io(bdi))
                         continue;
 
-                /*
-                 * If work allocation fails, do the writes inline. We drop
-                 * the lock and restart the list writeout. This should be OK,
-                 * since this happens rarely and because the writeout should
-                 * eventually make more free memory available.
-                 */
-                work = bdi_alloc_work(wbc);
-                if (!work) {
-                        struct writeback_control __wbc;
-
-                        /*
-                         * Not a data integrity writeout, just continue
-                         */
-                        if (!must_wait)
-                                continue;
-
-                        spin_unlock(&bdi_lock);
-                        __wbc = *wbc;
-                        __wbc.bdi = bdi;
-                        writeback_inodes_wbc(&__wbc);
-                        goto restart;
-                }
-                if (must_wait)
-                        list_add_tail(&work->wait_list, &list);
-
-                bdi_queue_work(bdi, work);
+                bdi_alloc_queue_work(bdi, wbc);
         }
 
         spin_unlock(&bdi_lock);
-
-        /*
-         * If this is for WB_SYNC_ALL, wait for pending work to complete
-         * before returning.
-         */
-        while (!list_empty(&list)) {
-                work = list_entry(list.next, struct bdi_work, wait_list);
-                list_del(&work->wait_list);
-                bdi_wait_on_work_clear(work);
-                call_rcu(&work->rcu_head, bdi_work_free);
-        }
 }
 
 /*
@@ -1177,6 +1134,7 @@ long sync_inodes_sb(struct super_block *sb)
 {
         struct writeback_control wbc = {
                 .sb             = sb,
+                .bdi            = sb->s_bdi,
                 .sync_mode      = WB_SYNC_ALL,
                 .range_start    = 0,
                 .range_end      = LLONG_MAX,
@@ -1184,7 +1142,7 @@ long sync_inodes_sb(struct super_block *sb)
         long nr_to_write = LONG_MAX; /* doesn't actually matter */
 
         wbc.nr_to_write = nr_to_write;
-        bdi_writeback_all(&wbc);
+        bdi_start_writeback(&wbc);
         wait_sb_inodes(&wbc);
         return nr_to_write - wbc.nr_to_write;
 }