Btrfs: Add a thread pool just for submit_bio

If a bio submission is after a lock holder waiting for the bio
on the work queue, it is possible to deadlock.  Move the bios
into their own pool.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index c6a710a668cb..e5c758e306d5 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1233,8 +1233,10 @@ struct btrfs_root *open_ctree(struct super_block *sb,
          * cannot dynamically grow.
          */
         btrfs_init_workers(&fs_info->workers, fs_info->thread_pool_size);
+        btrfs_init_workers(&fs_info->submit_workers, fs_info->thread_pool_size);
         btrfs_init_workers(&fs_info->endio_workers, fs_info->thread_pool_size);
         btrfs_start_workers(&fs_info->workers, 1);
+        btrfs_start_workers(&fs_info->submit_workers, 1);
         btrfs_start_workers(&fs_info->endio_workers, fs_info->thread_pool_size);
 
 
@@ -1343,6 +1345,7 @@ fail_sb_buffer:
         extent_io_tree_empty_lru(&BTRFS_I(fs_info->btree_inode)->io_tree);
         btrfs_stop_workers(&fs_info->workers);
         btrfs_stop_workers(&fs_info->endio_workers);
+        btrfs_stop_workers(&fs_info->submit_workers);
 fail_iput:
         iput(fs_info->btree_inode);
 fail:
@@ -1597,6 +1600,7 @@ int close_ctree(struct btrfs_root *root)
 
         btrfs_stop_workers(&fs_info->workers);
         btrfs_stop_workers(&fs_info->endio_workers);
+        btrfs_stop_workers(&fs_info->submit_workers);
 
         iput(fs_info->btree_inode);
 #if 0