[Cluster-devel] [PATCH] gfs2: Don't withdraw under a spin lock

[Andreas Gruenbacher <agruenba@redhat.com>]

In two places, the gfs2_io_error_bh macro is called while holding the
sd_ail_lock spin lock.  This isn't allowed because gfs2_io_error_bh
withdraws the filesystem, which can sleep because it issues a uevent.
To fix that, add a __gfs2_io_error_bh macro that doesn't withdraw the
filesystem, and withdraw the filesystem after releasing sd_ail_lock
where necessary.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/log.c  | 30 +++++++++++++++++++++---------
 fs/gfs2/util.c | 38 ++++++++++++++++++++------------------
 fs/gfs2/util.h | 10 +++++++---
 3 files changed, 48 insertions(+), 30 deletions(-)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 0248835625f1..b8e937190212 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -92,7 +92,8 @@ static void gfs2_remove_from_ail(struct gfs2_bufdata *bd)
 
 static int gfs2_ail1_start_one(struct gfs2_sbd *sdp,
 			       struct writeback_control *wbc,
-			       struct gfs2_trans *tr)
+			       struct gfs2_trans *tr,
+			       bool *withdraw)
 __releases(&sdp->sd_ail_lock)
 __acquires(&sdp->sd_ail_lock)
 {
@@ -107,8 +108,10 @@ __acquires(&sdp->sd_ail_lock)
 		gfs2_assert(sdp, bd->bd_tr == tr);
 
 		if (!buffer_busy(bh)) {
-			if (!buffer_uptodate(bh))
-				gfs2_io_error_bh(sdp, bh);
+			if (!buffer_uptodate(bh)) {
+				__gfs2_io_error_bh(sdp, bh);
+				*withdraw = true;
+			}
 			list_move(&bd->bd_ail_st_list, &tr->tr_ail2_list);
 			continue;
 		}
@@ -148,6 +151,7 @@ void gfs2_ail1_flush(struct gfs2_sbd *sdp, struct writeback_control *wbc)
 	struct list_head *head = &sdp->sd_ail1_list;
 	struct gfs2_trans *tr;
 	struct blk_plug plug;
+	bool withdraw = false;
 
 	trace_gfs2_ail_flush(sdp, wbc, 1);
 	blk_start_plug(&plug);
@@ -156,11 +160,13 @@ void gfs2_ail1_flush(struct gfs2_sbd *sdp, struct writeback_control *wbc)
 	list_for_each_entry_reverse(tr, head, tr_list) {
 		if (wbc->nr_to_write <= 0)
 			break;
-		if (gfs2_ail1_start_one(sdp, wbc, tr))
+		if (gfs2_ail1_start_one(sdp, wbc, tr, &withdraw))
 			goto restart;
 	}
 	spin_unlock(&sdp->sd_ail_lock);
 	blk_finish_plug(&plug);
+	if (withdraw)
+		gfs2_lm_withdraw(sdp, NULL);
 	trace_gfs2_ail_flush(sdp, wbc, 0);
 }
 
@@ -188,7 +194,8 @@ static void gfs2_ail1_start(struct gfs2_sbd *sdp)
  *
  */
 
-static void gfs2_ail1_empty_one(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
+static void gfs2_ail1_empty_one(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
+				bool *withdraw)
 {
 	struct gfs2_bufdata *bd, *s;
 	struct buffer_head *bh;
@@ -199,11 +206,12 @@ static void gfs2_ail1_empty_one(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
 		gfs2_assert(sdp, bd->bd_tr == tr);
 		if (buffer_busy(bh))
 			continue;
-		if (!buffer_uptodate(bh))
-			gfs2_io_error_bh(sdp, bh);
+		if (!buffer_uptodate(bh)) {
+			__gfs2_io_error_bh(sdp, bh);
+			*withdraw = true;
+		}
 		list_move(&bd->bd_ail_st_list, &tr->tr_ail2_list);
 	}
-
 }
 
 /**
@@ -218,10 +226,11 @@ static int gfs2_ail1_empty(struct gfs2_sbd *sdp)
 	struct gfs2_trans *tr, *s;
 	int oldest_tr = 1;
 	int ret;
+	bool withdraw = false;
 
 	spin_lock(&sdp->sd_ail_lock);
 	list_for_each_entry_safe_reverse(tr, s, &sdp->sd_ail1_list, tr_list) {
-		gfs2_ail1_empty_one(sdp, tr);
+		gfs2_ail1_empty_one(sdp, tr, &withdraw);
 		if (list_empty(&tr->tr_ail1_list) && oldest_tr)
 			list_move(&tr->tr_list, &sdp->sd_ail2_list);
 		else
@@ -230,6 +239,9 @@ static int gfs2_ail1_empty(struct gfs2_sbd *sdp)
 	ret = list_empty(&sdp->sd_ail1_list);
 	spin_unlock(&sdp->sd_ail_lock);
 
+	if (withdraw)
+		gfs2_lm_withdraw(sdp, "fatal: I/O error(s)\n");
+
 	return ret;
 }
 
diff --git a/fs/gfs2/util.c b/fs/gfs2/util.c
index 763d659db91b..59c811de0dc7 100644
--- a/fs/gfs2/util.c
+++ b/fs/gfs2/util.c
@@ -46,14 +46,16 @@ int gfs2_lm_withdraw(struct gfs2_sbd *sdp, const char *fmt, ...)
 	    test_and_set_bit(SDF_SHUTDOWN, &sdp->sd_flags))
 		return 0;
 
-	va_start(args, fmt);
+	if (fmt) {
+		va_start(args, fmt);
 
-	vaf.fmt = fmt;
-	vaf.va = &args;
+		vaf.fmt = fmt;
+		vaf.va = &args;
 
-	fs_err(sdp, "%pV", &vaf);
+		fs_err(sdp, "%pV", &vaf);
 
-	va_end(args);
+		va_end(args);
+	}
 
 	if (sdp->sd_args.ar_errors == GFS2_ERRORS_WITHDRAW) {
 		fs_err(sdp, "about to withdraw this file system\n");
@@ -246,21 +248,21 @@ int gfs2_io_error_i(struct gfs2_sbd *sdp, const char *function, char *file,
 }
 
 /**
- * gfs2_io_error_bh_i - Flag a buffer I/O error and withdraw
- * Returns: -1 if this call withdrew the machine,
- *          0 if it was already withdrawn
+ * gfs2_io_error_bh_i - Flag a buffer I/O error
+ * @withdraw: withdraw the filesystem
  */
 
-int gfs2_io_error_bh_i(struct gfs2_sbd *sdp, struct buffer_head *bh,
-		       const char *function, char *file, unsigned int line)
+void gfs2_io_error_bh_i(struct gfs2_sbd *sdp, struct buffer_head *bh,
+			const char *function, char *file, unsigned int line,
+			bool withdraw)
 {
-	int rv;
-	rv = gfs2_lm_withdraw(sdp,
-			      "fatal: I/O error\n"
-			      "  block = %llu\n"
-			      "  function = %s, file = %s, line = %u\n",
-			      (unsigned long long)bh->b_blocknr,
-			      function, file, line);
-	return rv;
+	fs_err(sdp,
+	       "fatal: I/O error\n"
+	       "  block = %llu\n"
+	       "  function = %s, file = %s, line = %u\n",
+	       (unsigned long long)bh->b_blocknr,
+	       function, file, line);
+	if (withdraw)
+		gfs2_lm_withdraw(sdp, NULL);
 }
 
diff --git a/fs/gfs2/util.h b/fs/gfs2/util.h
index 3926f95a6eb7..9d9583e842ac 100644
--- a/fs/gfs2/util.h
+++ b/fs/gfs2/util.h
@@ -136,11 +136,15 @@ int gfs2_io_error_i(struct gfs2_sbd *sdp, const char *function,
 gfs2_io_error_i((sdp), __func__, __FILE__, __LINE__);
 
 
-int gfs2_io_error_bh_i(struct gfs2_sbd *sdp, struct buffer_head *bh,
-		       const char *function, char *file, unsigned int line);
+void gfs2_io_error_bh_i(struct gfs2_sbd *sdp, struct buffer_head *bh,
+			const char *function, char *file, unsigned int line,
+			bool withdraw);
 
 #define gfs2_io_error_bh(sdp, bh) \
-gfs2_io_error_bh_i((sdp), (bh), __func__, __FILE__, __LINE__);
+gfs2_io_error_bh_i((sdp), (bh), __func__, __FILE__, __LINE__, true);
+
+#define __gfs2_io_error_bh(sdp, bh) \
+gfs2_io_error_bh_i((sdp), (bh), __func__, __FILE__, __LINE__, false);
 
 
 extern struct kmem_cache *gfs2_glock_cachep;
-- 
2.17.0