Btrfs: write out free space cache

This is a simple bit, just dump the free space cache out to our preallocated
inode when we're writing out dirty block groups.  There are a bunch of changes
in inode.c in order to account for special cases.  Mostly when we're doing the
writeout we're holding trans_mutex, so we need to use the nolock transacation
functions.  Also we can't do asynchronous completions since the async thread
could be blocked on already completed IO waiting for the transaction lock.  This
has been tested with xfstests and btrfs filesystem balance, as well as my ENOSPC
tests.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>

1 files changed, 16 insertions, 1 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 45cf64fc1e3e..77e5dabfd45a 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -481,9 +481,12 @@ static void end_workqueue_bio(struct bio *bio, int err)
         end_io_wq->work.flags = 0;
 
         if (bio->bi_rw & REQ_WRITE) {
-                if (end_io_wq->metadata)
+                if (end_io_wq->metadata == 1)
                         btrfs_queue_worker(&fs_info->endio_meta_write_workers,
                                            &end_io_wq->work);
+                else if (end_io_wq->metadata == 2)
+                        btrfs_queue_worker(&fs_info->endio_freespace_worker,
+                                           &end_io_wq->work);
                 else
                         btrfs_queue_worker(&fs_info->endio_write_workers,
                                            &end_io_wq->work);
@@ -497,6 +500,13 @@ static void end_workqueue_bio(struct bio *bio, int err)
         }
 }
 
+/*
+ * For the metadata arg you want
+ *
+ * 0 - if data
+ * 1 - if normal metadta
+ * 2 - if writing to the free space cache area
+ */
 int btrfs_bio_wq_end_io(struct btrfs_fs_info *info, struct bio *bio,
                         int metadata)
 {
@@ -1774,6 +1784,8 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         btrfs_init_workers(&fs_info->endio_write_workers, "endio-write",
                            fs_info->thread_pool_size,
                            &fs_info->generic_worker);
+        btrfs_init_workers(&fs_info->endio_freespace_worker, "freespace-write",
+                           1, &fs_info->generic_worker);
 
         /*
          * endios are largely parallel and should have a very
@@ -1794,6 +1806,7 @@ 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->endio_freespace_worker, 1);
 
         fs_info->bdi.ra_pages *= btrfs_super_num_devices(disk_super);
         fs_info->bdi.ra_pages = max(fs_info->bdi.ra_pages,
@@ -2035,6 +2048,7 @@ fail_sb_buffer:
         btrfs_stop_workers(&fs_info->endio_meta_workers);
         btrfs_stop_workers(&fs_info->endio_meta_write_workers);
         btrfs_stop_workers(&fs_info->endio_write_workers);
+        btrfs_stop_workers(&fs_info->endio_freespace_worker);
         btrfs_stop_workers(&fs_info->submit_workers);
 fail_iput:
         invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
@@ -2468,6 +2482,7 @@ int close_ctree(struct btrfs_root *root)
         btrfs_stop_workers(&fs_info->endio_meta_workers);
         btrfs_stop_workers(&fs_info->endio_meta_write_workers);
         btrfs_stop_workers(&fs_info->endio_write_workers);
+        btrfs_stop_workers(&fs_info->endio_freespace_worker);
         btrfs_stop_workers(&fs_info->submit_workers);
 
         btrfs_close_devices(fs_info->fs_devices);