cifs: simplify refcounting for oplock breaks

Currently, we take a sb->s_active reference and a cifsFileInfo reference
when an oplock break workqueue job is queued. This is unnecessary and
more complicated than it needs to be. Also as Al points out,
deactivate_super has non-trivial locking implications so it's best to
avoid that if we can.

Instead, just cancel any pending oplock breaks for this filehandle
synchronously in cifsFileInfo_put after taking it off the lists.
That should ensure that this job doesn't outlive the structures it
depends on.

Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 2 insertions, 25 deletions

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 378acdafa356..9f41a10523a1 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -314,6 +314,8 @@ void cifsFileInfo_put(struct cifsFileInfo *cifs_file)
         }
         spin_unlock(&cifs_file_list_lock);
 
+        cancel_work_sync(&cifs_file->oplock_break);
+
         if (!tcon->need_reconnect && !cifs_file->invalidHandle) {
                 int xid, rc;
 
@@ -2418,31 +2420,6 @@ void cifs_oplock_break(struct work_struct *work)
                                  cinode->clientCanCacheRead ? 1 : 0);
                 cFYI(1, "Oplock release rc = %d", rc);
         }
-
-        /*
-         * We might have kicked in before is_valid_oplock_break()
-         * finished grabbing reference for us.  Make sure it's done by
-         * waiting for cifs_file_list_lock.
-         */
-        spin_lock(&cifs_file_list_lock);
-        spin_unlock(&cifs_file_list_lock);
-
-        cifs_oplock_break_put(cfile);
-}
-
-/* must be called while holding cifs_file_list_lock */
-void cifs_oplock_break_get(struct cifsFileInfo *cfile)
-{
-        cifs_sb_active(cfile->dentry->d_sb);
-        cifsFileInfo_get(cfile);
-}
-
-void cifs_oplock_break_put(struct cifsFileInfo *cfile)
-{
-        struct super_block *sb = cfile->dentry->d_sb;
-
-        cifsFileInfo_put(cfile);
-        cifs_sb_deactive(sb);
 }
 
 const struct address_space_operations cifs_addr_ops = {