3 files changed, 88 insertions, 11 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index dbdada56950..a362dd617e9 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -691,17 +691,17 @@ struct btrfs_space_info {
 
         struct list_head list;
 
+        /* for controlling how we free up space for allocations */
+        wait_queue_head_t allocate_wait;
+        wait_queue_head_t flush_wait;
+        int allocating_chunk;
+        int flushing;
+
         /* for block groups in our same type */
         struct list_head block_groups;
         spinlock_t lock;
         struct rw_semaphore groups_sem;
         atomic_t caching_threads;
-
-        int allocating_chunk;
-        wait_queue_head_t wait;
-
-        int flushing;
-        wait_queue_head_t flush_wait;
 };
 
 /*
@@ -918,6 +918,7 @@ struct btrfs_fs_info {
         struct btrfs_workers endio_meta_write_workers;
         struct btrfs_workers endio_write_workers;
         struct btrfs_workers submit_workers;
+        struct btrfs_workers enospc_workers;
         /*
          * fixup workers take dirty pages that didn't properly go through
          * the cow mechanism and make them safe to write.  It happens
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 9903f042765..ac8927bdc33 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1762,6 +1762,9 @@ struct btrfs_root *open_ctree(struct super_block *sb,
                            min_t(u64, fs_devices->num_devices,
                            fs_info->thread_pool_size),
                            &fs_info->generic_worker);
+        btrfs_init_workers(&fs_info->enospc_workers, "enospc",
+                           fs_info->thread_pool_size,
+                           &fs_info->generic_worker);
 
         /* a higher idle thresh on the submit workers makes it much more
          * likely that bios will be send down in a sane order to the
@@ -1809,6 +1812,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         btrfs_start_workers(&fs_info->endio_meta_workers, 1);
         btrfs_start_workers(&fs_info->endio_meta_write_workers, 1);
         btrfs_start_workers(&fs_info->endio_write_workers, 1);
+        btrfs_start_workers(&fs_info->enospc_workers, 1);
 
         fs_info->bdi.ra_pages *= btrfs_super_num_devices(disk_super);
         fs_info->bdi.ra_pages = max(fs_info->bdi.ra_pages,
@@ -2023,6 +2027,7 @@ fail_sb_buffer:
         btrfs_stop_workers(&fs_info->endio_meta_write_workers);
         btrfs_stop_workers(&fs_info->endio_write_workers);
         btrfs_stop_workers(&fs_info->submit_workers);
+        btrfs_stop_workers(&fs_info->enospc_workers);
 fail_iput:
         invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
         iput(fs_info->btree_inode);
@@ -2449,6 +2454,7 @@ int close_ctree(struct btrfs_root *root)
         btrfs_stop_workers(&fs_info->endio_meta_write_workers);
         btrfs_stop_workers(&fs_info->endio_write_workers);
         btrfs_stop_workers(&fs_info->submit_workers);
+        btrfs_stop_workers(&fs_info->enospc_workers);
 
         btrfs_close_devices(fs_info->fs_devices);
         btrfs_mapping_tree_free(&fs_info->mapping_tree);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 3d1be0b77f8..53026806ae9 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2866,9 +2866,66 @@ static void check_force_delalloc(struct btrfs_space_info *meta_sinfo)
                 meta_sinfo->force_delalloc = 0;
 }
 
+struct async_flush {
+        struct btrfs_root *root;
+        struct btrfs_space_info *info;
+        struct btrfs_work work;
+};
+
+static noinline void flush_delalloc_async(struct btrfs_work *work)
+{
+        struct async_flush *async;
+        struct btrfs_root *root;
+        struct btrfs_space_info *info;
+
+        async = container_of(work, struct async_flush, work);
+        root = async->root;
+        info = async->info;
+
+        btrfs_start_delalloc_inodes(root);
+        wake_up(&info->flush_wait);
+        btrfs_wait_ordered_extents(root, 0);
+
+        spin_lock(&info->lock);
+        info->flushing = 0;
+        spin_unlock(&info->lock);
+        wake_up(&info->flush_wait);
+
+        kfree(async);
+}
+
+static void wait_on_flush(struct btrfs_space_info *info)
+{
+        DEFINE_WAIT(wait);
+        u64 used;
+
+        while (1) {
+                prepare_to_wait(&info->flush_wait, &wait,
+                                TASK_UNINTERRUPTIBLE);
+                spin_lock(&info->lock);
+                if (!info->flushing) {
+                        spin_unlock(&info->lock);
+                        break;
+                }
+
+                used = info->bytes_used + info->bytes_reserved +
+                        info->bytes_pinned + info->bytes_readonly +
+                        info->bytes_super + info->bytes_root +
+                        info->bytes_may_use + info->bytes_delalloc;
+                if (used < info->total_bytes) {
+                        spin_unlock(&info->lock);
+                        break;
+                }
+                spin_unlock(&info->lock);
+                schedule();
+        }
+        finish_wait(&info->flush_wait, &wait);
+}
+
 static void flush_delalloc(struct btrfs_root *root,
                                  struct btrfs_space_info *info)
 {
+        struct async_flush *async;
         bool wait = false;
 
         spin_lock(&info->lock);
@@ -2883,11 +2940,24 @@ static void flush_delalloc(struct btrfs_root *root,
         spin_unlock(&info->lock);
 
         if (wait) {
-                wait_event(info->flush_wait,
-                           !info->flushing);
+                wait_on_flush(info);
                 return;
         }
 
+        async = kzalloc(sizeof(*async), GFP_NOFS);
+        if (!async)
+                goto flush;
+
+        async->root = root;
+        async->info = info;
+        async->work.func = flush_delalloc_async;
+
+        btrfs_queue_worker(&root->fs_info->enospc_workers,
+                           &async->work);
+        wait_on_flush(info);
+        return;
+
+flush:
         btrfs_start_delalloc_inodes(root);
         btrfs_wait_ordered_extents(root, 0);
 
@@ -2927,7 +2997,7 @@ static int maybe_allocate_chunk(struct btrfs_root *root,
         if (!info->allocating_chunk) {
                 info->force_alloc = 1;
                 info->allocating_chunk = 1;
-                init_waitqueue_head(&info->wait);
+                init_waitqueue_head(&info->allocate_wait);
         } else {
                 wait = true;
         }
@@ -2935,7 +3005,7 @@ static int maybe_allocate_chunk(struct btrfs_root *root,
         spin_unlock(&info->lock);
 
         if (wait) {
-                wait_event(info->wait,
+                wait_event(info->allocate_wait,
                            !info->allocating_chunk);
                 return 1;
         }
@@ -2956,7 +3026,7 @@ out:
         spin_lock(&info->lock);
         info->allocating_chunk = 0;
         spin_unlock(&info->lock);
-        wake_up(&info->wait);
+        wake_up(&info->allocate_wait);
 
         if (ret)
                 return 0;