[Cluster-devel] [GFS2 PATCH] [v2] GFS2: Fix up some sparse warnings

[Bob Peterson <rpeterso@redhat.com>]

Hi,

I've been doing some investigation with regard to Andy Price's
questions about the glock / rhashtable portion of this patch.

It turns out that the rhashtable code in function glock_hash_walk
was patterned after the code in function tipc_sk_reinit() in
net/tips/socket.c. The loop in Andy's question was added recently
by Herbert Xu  in commit 40f9f439706073b4b0a654b3b99e18296b7990b3
and comments in that patch explain why the loop was added.
This differs, however, from net/netlink/diag.c which does not have
the loop.

As far as I can tell, the difference between having and not having
the loop comes down to what happens when an rhashtable resize
event occurs: Would you rather have it (a) process some
unpredictable number of glocks twice, or (b) skip some altogether?

Since the callers of function glock_hash_walk are gfs2_glock_thaw
and gfs2_gl_hash_clear, it makes more sense to me to process them
twice than not at all.

In doing this investigation, I found a bug in the original tipc
code, and submitted a patch for it this morning. That bug was
one I has proposed fixing with version 1 of this patch.

I've therefore revised this patch to (a) use IS_ERR(gl) rather
than just (gl) as Andy suggested. (b) Added a goto instead of
using braces, so that it more closely matches the patched tipc
code, and (c) got rid of some parenthesis to appease Andreas.

Bob Peterson

Patch description:
------------------
This patch cleans up various pieces of GFS2 to avoid sparse errors.
This doesn't fix them all, but it fixes several. The first error,
in function glock_hash_walk was a genuine bug where the rhashtable
could be started and not stopped.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
---
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index ffca19598525..4178417249c3 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -1550,14 +1550,15 @@ static void glock_hash_walk(glock_examiner examiner, const struct gfs2_sbd *sdp)
 
 	do {
 		gl = ERR_PTR(rhashtable_walk_start(&iter));
-		if (gl)
-			continue;
+		if (IS_ERR(gl))
+			goto walk_stop;
 
 		while ((gl = rhashtable_walk_next(&iter)) && !IS_ERR(gl))
-			if ((gl->gl_name.ln_sbd == sdp) &&
+			if (gl->gl_name.ln_sbd == sdp &&
 			    lockref_get_not_dead(&gl->gl_lockref))
 				examiner(gl);
 
+walk_stop:
 		rhashtable_walk_stop(&iter);
 	} while (cond_resched(), gl == ERR_PTR(-EAGAIN));
 
@@ -1940,6 +1941,7 @@ static void gfs2_glock_iter_next(struct gfs2_glock_iter *gi)
 }
 
 static void *gfs2_glock_seq_start(struct seq_file *seq, loff_t *pos)
+	__acquires(RCU)
 {
 	struct gfs2_glock_iter *gi = seq->private;
 	loff_t n = *pos;
@@ -1972,6 +1974,7 @@ static void *gfs2_glock_seq_next(struct seq_file *seq, void *iter_ptr,
 }
 
 static void gfs2_glock_seq_stop(struct seq_file *seq, void *iter_ptr)
+	__releases(RCU)
 {
 	struct gfs2_glock_iter *gi = seq->private;
 
diff --git a/fs/gfs2/lock_dlm.c b/fs/gfs2/lock_dlm.c
index 1d98b8a36eb3..65f33a0ac190 100644
--- a/fs/gfs2/lock_dlm.c
+++ b/fs/gfs2/lock_dlm.c
@@ -23,8 +23,6 @@
 #include "sys.h"
 #include "trace_gfs2.h"
 
-extern struct workqueue_struct *gfs2_control_wq;
-
 /**
  * gfs2_update_stats - Update time based stats
  * @mv: Pointer to mean/variance structure to update
@@ -1176,7 +1174,7 @@ static void gdlm_recovery_result(struct gfs2_sbd *sdp, unsigned int jid,
 	spin_unlock(&ls->ls_recover_spin);
 }
 
-const struct dlm_lockspace_ops gdlm_lockspace_ops = {
+static const struct dlm_lockspace_ops gdlm_lockspace_ops = {
 	.recover_prep = gdlm_recover_prep,
 	.recover_slot = gdlm_recover_slot,
 	.recover_done = gdlm_recover_done,
diff --git a/fs/gfs2/main.c b/fs/gfs2/main.c
index 0a89e6f7a314..899329cfd733 100644
--- a/fs/gfs2/main.c
+++ b/fs/gfs2/main.c
@@ -32,8 +32,6 @@
 #include "dir.h"
 #include "glops.h"
 
-struct workqueue_struct *gfs2_control_wq;
-
 static void gfs2_init_inode_once(void *foo)
 {
 	struct gfs2_inode *ip = foo;
diff --git a/fs/gfs2/util.h b/fs/gfs2/util.h
index c81295f407f6..3926f95a6eb7 100644
--- a/fs/gfs2/util.h
+++ b/fs/gfs2/util.h
@@ -151,6 +151,7 @@ extern struct kmem_cache *gfs2_rgrpd_cachep;
 extern struct kmem_cache *gfs2_quotad_cachep;
 extern struct kmem_cache *gfs2_qadata_cachep;
 extern mempool_t *gfs2_page_pool;
+extern struct workqueue_struct *gfs2_control_wq;
 
 static inline unsigned int gfs2_tune_get_i(struct gfs2_tune *gt,
 					   unsigned int *p)
diff --git a/fs/gfs2/xattr.c b/fs/gfs2/xattr.c
index 54179554c7d2..cf694de4991a 100644
--- a/fs/gfs2/xattr.c
+++ b/fs/gfs2/xattr.c
@@ -25,6 +25,7 @@
 #include "meta_io.h"
 #include "quota.h"
 #include "rgrp.h"
+#include "super.h"
 #include "trans.h"
 #include "util.h"