Btrfs: fix num_workers_starting bug and other bugs in async thread

Al pointed out we have some random problems with the way we account for
num_workers_starting in the async thread stuff.  First of all we need to make
sure to decrement num_workers_starting if we fail to start the worker, so make
__btrfs_start_workers do this.  Also fix __btrfs_start_workers so that it
doesn't call btrfs_stop_workers(), there is no point in stopping everybody if we
failed to create a worker.  Also check_pending_worker_creates needs to call
__btrfs_start_work in it's work function since it already increments
num_workers_starting.

People only start one worker at a time, so get rid of the num_workers argument
everywhere, and make btrfs_queue_worker a void since it will always succeed.
Thanks,

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

1 files changed, 21 insertions, 13 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 94abc25392f6..3f9d5551e582 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2194,19 +2194,27 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         fs_info->endio_meta_write_workers.idle_thresh = 2;
         fs_info->readahead_workers.idle_thresh = 2;
 
-        btrfs_start_workers(&fs_info->workers, 1);
-        btrfs_start_workers(&fs_info->generic_worker, 1);
-        btrfs_start_workers(&fs_info->submit_workers, 1);
-        btrfs_start_workers(&fs_info->delalloc_workers, 1);
-        btrfs_start_workers(&fs_info->fixup_workers, 1);
-        btrfs_start_workers(&fs_info->endio_workers, 1);
-        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);
-        btrfs_start_workers(&fs_info->delayed_workers, 1);
-        btrfs_start_workers(&fs_info->caching_workers, 1);
-        btrfs_start_workers(&fs_info->readahead_workers, 1);
+        /*
+         * btrfs_start_workers can really only fail because of ENOMEM so just
+         * return -ENOMEM if any of these fail.
+         */
+        ret = btrfs_start_workers(&fs_info->workers);
+        ret |= btrfs_start_workers(&fs_info->generic_worker);
+        ret |= btrfs_start_workers(&fs_info->submit_workers);
+        ret |= btrfs_start_workers(&fs_info->delalloc_workers);
+        ret |= btrfs_start_workers(&fs_info->fixup_workers);
+        ret |= btrfs_start_workers(&fs_info->endio_workers);
+        ret |= btrfs_start_workers(&fs_info->endio_meta_workers);
+        ret |= btrfs_start_workers(&fs_info->endio_meta_write_workers);
+        ret |= btrfs_start_workers(&fs_info->endio_write_workers);
+        ret |= btrfs_start_workers(&fs_info->endio_freespace_worker);
+        ret |= btrfs_start_workers(&fs_info->delayed_workers);
+        ret |= btrfs_start_workers(&fs_info->caching_workers);
+        ret |= btrfs_start_workers(&fs_info->readahead_workers);
+        if (ret) {
+                ret = -ENOMEM;
+                goto fail_sb_buffer;
+        }
 
         fs_info->bdi.ra_pages *= btrfs_super_num_devices(disk_super);
         fs_info->bdi.ra_pages = max(fs_info->bdi.ra_pages,