gfs2: use workqueue instead of slow-work

Workqueue can now handle high concurrency.  Convert gfs to use
workqueue instead of slow-work.

* Steven pointed out that recovery path might be run from allocation
  path and thus requires forward progress guarantee without memory
  allocation.  Create and use gfs_recovery_wq with rescuer.  Please
  note that forward progress wasn't guaranteed with slow-work.

* Updated to use non-reentrant workqueue.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 8 insertions, 6 deletions

diff --git a/fs/gfs2/main.c b/fs/gfs2/main.c
index fb2a5f93b7c3..b1e9630eb46a 100644
--- a/fs/gfs2/main.c
+++ b/fs/gfs2/main.c
@@ -15,7 +15,6 @@
 #include <linux/init.h>
 #include <linux/gfs2_ondisk.h>
 #include <asm/atomic.h>
-#include <linux/slow-work.h>
 
 #include "gfs2.h"
 #include "incore.h"
@@ -24,6 +23,7 @@
 #include "util.h"
 #include "glock.h"
 #include "quota.h"
+#include "recovery.h"
 
 static struct shrinker qd_shrinker = {
         .shrink = gfs2_shrink_qd_memory,
@@ -138,9 +138,11 @@ static int __init init_gfs2_fs(void)
         if (error)
                 goto fail_unregister;
 
-        error = slow_work_register_user(THIS_MODULE);
-        if (error)
-                goto fail_slow;
+        error = -ENOMEM;
+        gfs_recovery_wq = alloc_workqueue("gfs_recovery",
+                                          WQ_NON_REENTRANT | WQ_RESCUER, 0);
+        if (!gfs_recovery_wq)
+                goto fail_wq;
 
         gfs2_register_debugfs();
 
@@ -148,7 +150,7 @@ static int __init init_gfs2_fs(void)
 
         return 0;
 
-fail_slow:
+fail_wq:
         unregister_filesystem(&gfs2meta_fs_type);
 fail_unregister:
         unregister_filesystem(&gfs2_fs_type);
@@ -190,7 +192,7 @@ static void __exit exit_gfs2_fs(void)
         gfs2_unregister_debugfs();
         unregister_filesystem(&gfs2_fs_type);
         unregister_filesystem(&gfs2meta_fs_type);
-        slow_work_unregister_user(THIS_MODULE);
+        destroy_workqueue(gfs_recovery_wq);
 
         kmem_cache_destroy(gfs2_quotad_cachep);
         kmem_cache_destroy(gfs2_rgrpd_cachep);