[Cluster-devel] [GFS2 v8 PATCH 08/22] gfs2: Allow some glocks to be used during withdraw

[Bob Peterson]

We need to allow some glocks to be enqueued, dequeued, promoted, and demoted
when we're withdrawn. For example, to maintain metadata integrity, we should
disallow the use of inode and rgrp glocks when withdrawn. Other glocks, like
iopen or the transaction glocks may be safely used because none of their
metadata goes through the journal. So in general, we should disallow all
glocks with an address space, and allow all the others. One exception is:
we need to allow our active journal to be demoted so others may recover it.

Allowing glocks after withdraw gives us the ability to take appropriate
action (in a following patch) to have our journal properly replayed by
another node rather than just abandoning the current transactions and
pretending nothing bad happened, leaving the other nodes free to modify
the blocks we had in our journal, which may result in file system
corruption.

Signed-off-by: Bob Peterson <rpeterso at redhat.com>
---
 fs/gfs2/glock.c  | 29 +++++++++++++++++++++++++++--
 fs/gfs2/glops.c  |  4 ++--
 fs/gfs2/incore.h |  1 +
 3 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 46c50090c3ca..c8b95a8842f5 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -133,6 +133,31 @@ static void gfs2_glock_dealloc(struct rcu_head *rcu)
 	}
 }
 
+/**
+ * allow_while_withdrawn - determine if we can use this glock while withdrawn
+ * @gl: the glock
+ *
+ * We need to allow some glocks to be enqueued, dequeued, promoted, and demoted
+ * when we're withdrawn. For example, to maintain metadata integrity, we should
+ * disallow the use of inode and rgrp glocks when withdrawn. Other glocks, like
+ * iopen or the transaction glocks may be safely used because none of their
+ * metadata goes through the journal. So in general, we should disallow all
+ * glocks that are journaled, and allow all the others. One exception is:
+ * we need to allow our active journal to be demoted so others may recover it.
+ */
+static bool allow_while_withdrawn(struct gfs2_glock *gl)
+{
+	struct gfs2_sbd *sdp;
+
+	if (!(gl->gl_ops->go_flags & GLOF_JOURNALED))
+		return true;
+
+	sdp = gl->gl_name.ln_sbd;
+	if (!sdp->sd_jdesc || gl->gl_object == sdp->sd_jdesc->jd_inode)
+		return true;
+	return false;
+}
+
 void gfs2_glock_free(struct gfs2_glock *gl)
 {
 	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
@@ -549,7 +574,7 @@ __acquires(&gl->gl_lockref.lock)
 	unsigned int lck_flags = (unsigned int)(gh ? gh->gh_flags : 0);
 	int ret;
 
-	if (unlikely(gfs2_withdrawn(sdp)) &&
+	if (unlikely(gfs2_withdrawn(sdp)) && !allow_while_withdrawn(gl) &&
 	    target != LM_ST_UNLOCKED)
 		return;
 	lck_flags &= (LM_FLAG_TRY | LM_FLAG_TRY_1CB | LM_FLAG_NOEXP |
@@ -1197,7 +1222,7 @@ int gfs2_glock_nq(struct gfs2_holder *gh)
 	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
 	int error = 0;
 
-	if (unlikely(gfs2_withdrawn(sdp)))
+	if (unlikely(gfs2_withdrawn(sdp)) && !allow_while_withdrawn(gl))
 		return -EIO;
 
 	if (test_bit(GLF_LRU, &gl->gl_flags))
diff --git a/fs/gfs2/glops.c b/fs/gfs2/glops.c
index dec5e245b991..04f55e5b8bf1 100644
--- a/fs/gfs2/glops.c
+++ b/fs/gfs2/glops.c
@@ -587,7 +587,7 @@ const struct gfs2_glock_operations gfs2_inode_glops = {
 	.go_lock = inode_go_lock,
 	.go_dump = inode_go_dump,
 	.go_type = LM_TYPE_INODE,
-	.go_flags = GLOF_ASPACE | GLOF_LRU,
+	.go_flags = GLOF_ASPACE | GLOF_LRU | GLOF_JOURNALED,
 };
 
 const struct gfs2_glock_operations gfs2_rgrp_glops = {
@@ -596,7 +596,7 @@ const struct gfs2_glock_operations gfs2_rgrp_glops = {
 	.go_lock = gfs2_rgrp_go_lock,
 	.go_dump = gfs2_rgrp_dump,
 	.go_type = LM_TYPE_RGRP,
-	.go_flags = GLOF_LVB,
+	.go_flags = GLOF_LVB | GLOF_JOURNALED,
 };
 
 const struct gfs2_glock_operations gfs2_freeze_glops = {
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index d37698502d5d..f6ec52776408 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -247,6 +247,7 @@ struct gfs2_glock_operations {
 #define GLOF_ASPACE 1
 #define GLOF_LVB    2
 #define GLOF_LRU    4
+#define GLOF_JOURNALED 8 /* goes through the journal */
 };
 
 enum {
-- 
2.23.0