gfs2: Allow some glocks to be used during withdraw

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when we're withdrawn.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disallow the use of inode and rgrp glocks when withdrawn.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@redhat.com>

1 files changed, 29 insertions, 4 deletions

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 1cb471a8bc87..454d94dd8933 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -133,6 +133,33 @@ static void gfs2_glock_dealloc(struct rcu_head *rcu)
 	}
 }
 
+/**
+ * glock_blocked_by_withdraw - determine if we can still use a glock
+ * @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+ * when we're withdrawn.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+ * disallow the use of inode and rgrp glocks when withdrawn.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 promoted and demoted so others
+ * may recover it and we can reacquire it when they're done.
+ */
+static bool glock_blocked_by_withdraw(struct gfs2_glock *gl)
+{
+	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
+
+	if (likely(!gfs2_withdrawn(sdp)))
+		return false;
+	if (gl->gl_ops->go_flags & GLOF_NONDISK)
+		return false;
+	if (!sdp->sd_jdesc ||
+	    gl->gl_name.ln_number == sdp->sd_jdesc->jd_no_addr)
+		return false;
+	return true;
+}
+
 void gfs2_glock_free(struct gfs2_glock *gl)
 {
 	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
@@ -549,8 +576,7 @@ __acquires(&gl->gl_lockref.lock)
 	unsigned int lck_flags = (unsigned int)(gh ? gh->gh_flags : 0);
 	int ret;
 
-	if (unlikely(gfs2_withdrawn(sdp)) &&
-	    target != LM_ST_UNLOCKED)
+	if (target != LM_ST_UNLOCKED && glock_blocked_by_withdraw(gl))
 		return;
 	lck_flags &= (LM_FLAG_TRY | LM_FLAG_TRY_1CB | LM_FLAG_NOEXP |
 		      LM_FLAG_PRIORITY);
@@ -1194,10 +1220,9 @@ trap_recursive:
 int gfs2_glock_nq(struct gfs2_holder *gh)
 {
 	struct gfs2_glock *gl = gh->gh_gl;
-	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
 	int error = 0;
 
-	if (unlikely(gfs2_withdrawn(sdp)))
+	if (glock_blocked_by_withdraw(gl))
 		return -EIO;
 
 	if (test_bit(GLF_LRU, &gl->gl_flags))