GFS2: Withdraw for IO errors writing to the journal or statfs

Before this patch, if GFS2 encountered IO errors while writing to
the journal, it would not report the problem, so they would go
unnoticed, sometimes for many hours. Sometimes this would only be
noticed later, when recovery tried to do journal replay and failed
due to invalid metadata at the blocks that resulted in IO errors.

This patch makes GFS2's log daemon check for IO errors. If it
encounters one, it withdraws from the file system and reports
why in dmesg. A similar action is taken when IO errors occur when
writing to the system statfs file.

These errors are also reported back to any callers of fsync, since
that requires the journal to be flushed. Therefore, any IO errors
that would previously go unnoticed are now noticed and the file
system is withdrawn as early as possible, thus preventing further
file system damage.

Also note that this reintroduces superblock variable sd_log_error,
which Christoph removed with commit f729b66f.
Signed-off-by: Bob Peterson <rpeterso@redhat.com>

fs/gfs2/incore.h

@@ -817,6 +817,7 @@ struct gfs2_sbd {
 	atomic_t sd_log_in_flight;
 	struct bio *sd_log_bio;
 	wait_queue_head_t sd_log_flush_wait;
+	int sd_log_error;
 
 	atomic_t sd_reserving_log;
 	wait_queue_head_t sd_reserving_log_wait;

fs/gfs2/log.c

@@ -923,6 +923,15 @@ int gfs2_logd(void *data)
 
 	while (!kthread_should_stop()) {
 
+		/* Check for errors writing to the journal */
+		if (sdp->sd_log_error) {
+			gfs2_lm_withdraw(sdp,
+					 "GFS2: fsid=%s: error %d: "
+					 "withdrawing the file system to "
+					 "prevent further damage.\n",
+					 sdp->sd_fsname, sdp->sd_log_error);
+		}
+
 		did_flush = false;
 		if (gfs2_jrnl_flush_reqd(sdp) || t == 0) {
 			gfs2_ail1_empty(sdp);

fs/gfs2/lops.c

@@ -207,8 +207,11 @@ static void gfs2_end_log_write(struct bio *bio)
 	struct page *page;
 	int i;
 
-	if (bio->bi_status)
-		fs_err(sdp, "Error %d writing to log\n", bio->bi_status);
+	if (bio->bi_status) {
+		fs_err(sdp, "Error %d writing to journal, jid=%u\n",
+		       bio->bi_status, sdp->sd_jdesc->jd_jid);
+		wake_up(&sdp->sd_logd_waitq);
+	}
 
 	bio_for_each_segment_all(bvec, bio, i) {
 		page = bvec->bv_page;

fs/gfs2/quota.c

@@ -1474,8 +1474,11 @@ static void quotad_error(struct gfs2_sbd *sdp, const char *msg, int error)
 {
 	if (error == 0 || error == -EROFS)
 		return;
-	if (!test_bit(SDF_SHUTDOWN, &sdp->sd_flags))
+	if (!test_bit(SDF_SHUTDOWN, &sdp->sd_flags)) {
 		fs_err(sdp, "gfs2_quotad: %s error %d\n", msg, error);
+		sdp->sd_log_error = error;
+		wake_up(&sdp->sd_logd_waitq);
+	}
 }
 
 static void quotad_check_timeo(struct gfs2_sbd *sdp, const char *msg,

fs/gfs2/super.c

@@ -944,9 +944,9 @@ static int gfs2_sync_fs(struct super_block *sb, int wait)
 	struct gfs2_sbd *sdp = sb->s_fs_info;
 
 	gfs2_quota_sync(sb, -1);
-	if (wait && sdp)
+	if (wait)
 		gfs2_log_flush(sdp, NULL, NORMAL_FLUSH);
-	return 0;
+	return sdp->sd_log_error;
 }
 
 void gfs2_freeze_func(struct work_struct *work)