cifs: use workqueue instead of slow-work

Workqueue can now handle high concurrency.  Use system_nrt_wq
instead of slow-work.

* Updated is_valid_oplock_break() to not call cifs_oplock_break_put()
  as advised by Steve French.  It might cause deadlock.  Instead,
  reference is increased after queueing succeeded and
  cifs_oplock_break() briefly grabs GlobalSMBSeslock before putting
  the cfile to make sure it doesn't put before the matching get is
  finished.

* Anton Blanchard reported that cifs conversion was using now gone
  system_single_wq.  Use system_nrt_wq which provides non-reentrance
  guarantee which is enough and much better.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Steve French <sfrench@samba.org>
Cc: Anton Blanchard <anton@samba.org>

1 files changed, 5 insertions, 3 deletions

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index a88479ceaad5..f5a1f9bb3a9f 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -19,7 +19,7 @@
 #include <linux/in.h>
 #include <linux/in6.h>
 #include <linux/slab.h>
-#include <linux/slow-work.h>
+#include <linux/workqueue.h>
 #include "cifs_fs_sb.h"
 #include "cifsacl.h"
 /*
@@ -363,7 +363,7 @@ struct cifsFileInfo {
         atomic_t count;         /* reference count */
         struct mutex fh_mutex; /* prevents reopen race after dead ses*/
         struct cifs_search_info srch_inf;
-        struct slow_work oplock_break; /* slow_work job for oplock breaks */
+        struct work_struct oplock_break; /* work for oplock breaks */
 };
 
 /* Take a reference on the file private data */
@@ -732,4 +732,6 @@ GLOBAL_EXTERN unsigned int cifs_min_rcv;    /* min size of big ntwrk buf pool */
 GLOBAL_EXTERN unsigned int cifs_min_small;  /* min size of small buf pool */
 GLOBAL_EXTERN unsigned int cifs_max_pending; /* MAX requests at once to server*/
 
-extern const struct slow_work_ops cifs_oplock_break_ops;
+void cifs_oplock_break(struct work_struct *work);
+void cifs_oplock_break_get(struct cifsFileInfo *cfile);
+void cifs_oplock_break_put(struct cifsFileInfo *cfile);