gfs2: drain the ail2 list after io errors

Before this patch, gfs2_logd continually tried to flush its journal
log, after the file system is withdrawn. We don't want to write anything
to the journal, lest we add corruption. Best course of action is to
drain the ail1 into the ail2 list (via gfs2_ail1_empty) then drain the
ail2 list with a new function, ail2_drain.
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Reviewed-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/log.c

@@ -299,19 +299,16 @@ static void gfs2_ail1_wait(struct gfs2_sbd *sdp)
 }
 
 /**
- * gfs2_ail2_empty_one - Check whether or not a trans in the AIL has been synced
- * @sdp: the filesystem
- * @ai: the AIL entry
- *
+ * gfs2_ail_empty_tr - empty one of the ail lists for a transaction
  */
 
-static void gfs2_ail2_empty_one(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
+static void gfs2_ail_empty_tr(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
+			      struct list_head *head)
 {
-	struct list_head *head = &tr->tr_ail2_list;
 	struct gfs2_bufdata *bd;
 
 	while (!list_empty(head)) {
-		bd = list_entry(head->prev, struct gfs2_bufdata,
+		bd = list_first_entry(head, struct gfs2_bufdata,
 				      bd_ail_st_list);
 		gfs2_assert(sdp, bd->bd_tr == tr);
 		gfs2_remove_from_ail(bd);
@@ -334,7 +331,7 @@ static void ail2_empty(struct gfs2_sbd *sdp, unsigned int new_tail)
 		if (!rm)
 			continue;
 
-		gfs2_ail2_empty_one(sdp, tr);
+		gfs2_ail_empty_tr(sdp, tr, &tr->tr_ail2_list);
 		list_del(&tr->tr_list);
 		gfs2_assert_warn(sdp, list_empty(&tr->tr_ail1_list));
 		gfs2_assert_warn(sdp, list_empty(&tr->tr_ail2_list));
@@ -801,6 +798,40 @@ static void log_write_header(struct gfs2_sbd *sdp, u32 flags)
 		log_pull_tail(sdp, tail);
 }
 
+/**
+ * ail_drain - drain the ail lists after a withdraw
+ * @sdp: Pointer to GFS2 superblock
+ */
+static void ail_drain(struct gfs2_sbd *sdp)
+{
+	struct gfs2_trans *tr;
+
+	spin_lock(&sdp->sd_ail_lock);
+	/*
+	 * For transactions on the sd_ail1_list we need to drain both the
+	 * ail1 and ail2 lists. That's because function gfs2_ail1_start_one
+	 * (temporarily) moves items from its tr_ail1 list to tr_ail2 list
+	 * before revokes are sent for that block. Items on the sd_ail2_list
+	 * should have already gotten beyond that point, so no need.
+	 */
+	while (!list_empty(&sdp->sd_ail1_list)) {
+		tr = list_first_entry(&sdp->sd_ail1_list, struct gfs2_trans,
+				      tr_list);
+		gfs2_ail_empty_tr(sdp, tr, &tr->tr_ail1_list);
+		gfs2_ail_empty_tr(sdp, tr, &tr->tr_ail2_list);
+		list_del(&tr->tr_list);
+		kfree(tr);
+	}
+	while (!list_empty(&sdp->sd_ail2_list)) {
+		tr = list_first_entry(&sdp->sd_ail2_list, struct gfs2_trans,
+				      tr_list);
+		gfs2_ail_empty_tr(sdp, tr, &tr->tr_ail2_list);
+		list_del(&tr->tr_list);
+		kfree(tr);
+	}
+	spin_unlock(&sdp->sd_ail_lock);
+}
+
 /**
  * gfs2_log_flush - flush incore transaction(s)
  * @sdp: the filesystem
@@ -811,11 +842,18 @@ static void log_write_header(struct gfs2_sbd *sdp, u32 flags)
 
 void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 {
-	struct gfs2_trans *tr;
+	struct gfs2_trans *tr = NULL;
 	enum gfs2_freeze_state state = atomic_read(&sdp->sd_freeze_state);
 
 	down_write(&sdp->sd_log_flush_lock);
 
+	/*
+	 * Do this check while holding the log_flush_lock to prevent new
+	 * buffers from being added to the ail via gfs2_pin()
+	 */
+	if (gfs2_withdrawn(sdp))
+		goto out;
+
 	/* Log might have been flushed while we waited for the flush lock */
 	if (gl && !test_bit(GLF_LFLUSH, &gl->gl_flags)) {
 		up_write(&sdp->sd_log_flush_lock);
@@ -843,8 +881,14 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 			sdp->sd_log_num_revoke == sdp->sd_log_committed_revoke);
 
 	gfs2_ordered_write(sdp);
+	if (gfs2_withdrawn(sdp))
+		goto out;
 	lops_before_commit(sdp, tr);
+	if (gfs2_withdrawn(sdp))
+		goto out;
 	gfs2_log_submit_bio(&sdp->sd_log_bio, REQ_OP_WRITE);
+	if (gfs2_withdrawn(sdp))
+		goto out;
 
 	if (sdp->sd_log_head != sdp->sd_log_flush_head) {
 		log_flush_wait(sdp);
@@ -854,6 +898,8 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 		trace_gfs2_log_blocks(sdp, -1);
 		log_write_header(sdp, flags);
 	}
+	if (gfs2_withdrawn(sdp))
+		goto out;
 	lops_after_commit(sdp, tr);
 
 	gfs2_log_lock(sdp);
@@ -892,6 +938,11 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 	}
 
 out:
+	if (gfs2_withdrawn(sdp)) {
+		ail_drain(sdp); /* frees all transactions */
+		tr = NULL;
+	}
+
 	trace_gfs2_log_flush(sdp, 0, flags);
 	up_write(&sdp->sd_log_flush_lock);
 

fs/gfs2/trans.c

@@ -228,6 +228,10 @@ void gfs2_trans_add_meta(struct gfs2_glock *gl, struct buffer_head *bh)
 		fs_info(sdp, "GFS2:adding buf while frozen\n");
 		gfs2_assert_withdraw(sdp, 0);
 	}
+	if (unlikely(gfs2_withdrawn(sdp))) {
+		fs_info(sdp, "GFS2:adding buf while withdrawn! 0x%llx\n",
+			(unsigned long long)bd->bd_bh->b_blocknr);
+	}
 	gfs2_pin(sdp, bd->bd_bh);
 	mh->__pad0 = cpu_to_be64(0);
 	mh->mh_jid = cpu_to_be32(sdp->sd_jdesc->jd_jid);