gfs2: Don't start unnecessary transactions during log flush

Commit 8d391972ae2d ("gfs2: Remove __gfs2_writepage()") changed the log
flush code in gfs2_ail1_start_one() to call aops->writepages() instead
of aops->writepage().  For jdata inodes, this means that we will now try
to reserve log space and start a transaction before we can determine
that the pages in question have already been journaled.  When this
happens in the context of gfs2_logd(), it can now appear that not enough
log space is available for freeing up log space, and we will lock up.

Fix that by issuing journal writes directly instead of going through
aops->writepages() in the log flush code.

Fixes: 8d391972ae2d ("gfs2: Remove __gfs2_writepage()")
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

3 files changed, 38 insertions, 1 deletions

diff --git a/fs/gfs2/aops.c b/fs/gfs2/aops.c
index 1a3a420316fa..14f204cd5a82 100644
--- a/fs/gfs2/aops.c
+++ b/fs/gfs2/aops.c
@@ -118,6 +118,37 @@ static int __gfs2_jdata_write_folio(struct folio *folio,
 }
 
 /**
+ * gfs2_jdata_writeback - Write jdata folios to the log
+ * @mapping: The mapping to write
+ * @wbc: The writeback control
+ *
+ * Returns: errno
+ */
+int gfs2_jdata_writeback(struct address_space *mapping, struct writeback_control *wbc)
+{
+	struct inode *inode = mapping->host;
+	struct gfs2_inode *ip = GFS2_I(inode);
+	struct gfs2_sbd *sdp = GFS2_SB(mapping->host);
+	struct folio *folio = NULL;
+	int error;
+
+	BUG_ON(current->journal_info);
+	if (gfs2_assert_withdraw(sdp, ip->i_gl->gl_state == LM_ST_EXCLUSIVE))
+		return 0;
+
+	while ((folio = writeback_iter(mapping, wbc, folio, &error))) {
+		if (folio_test_checked(folio)) {
+			folio_redirty_for_writepage(wbc, folio);
+			folio_unlock(folio);
+			continue;
+		}
+		error = __gfs2_jdata_write_folio(folio, wbc);
+	}
+
+	return error;
+}
+
+/**
  * gfs2_writepages - Write a bunch of dirty pages back to disk
  * @mapping: The mapping to write
  * @wbc: Write-back control
diff --git a/fs/gfs2/aops.h b/fs/gfs2/aops.h
index f9fa41aaeaf4..bf002522a782 100644
--- a/fs/gfs2/aops.h
+++ b/fs/gfs2/aops.h
@@ -9,5 +9,6 @@
 #include "incore.h"
 
 void adjust_fs_space(struct inode *inode);
+int gfs2_jdata_writeback(struct address_space *mapping, struct writeback_control *wbc);
 
 #endif /* __AOPS_DOT_H__ */
diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index f9c5089783d2..115c4ac457e9 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -31,6 +31,7 @@
 #include "dir.h"
 #include "trace_gfs2.h"
 #include "trans.h"
+#include "aops.h"
 
 static void gfs2_log_shutdown(struct gfs2_sbd *sdp);
 
@@ -131,7 +132,11 @@ __acquires(&sdp->sd_ail_lock)
 		if (!mapping)
 			continue;
 		spin_unlock(&sdp->sd_ail_lock);
-		ret = mapping->a_ops->writepages(mapping, wbc);
+		BUG_ON(GFS2_SB(mapping->host) != sdp);
+		if (gfs2_is_jdata(GFS2_I(mapping->host)))
+			ret = gfs2_jdata_writeback(mapping, wbc);
+		else
+			ret = mapping->a_ops->writepages(mapping, wbc);
 		if (need_resched()) {
 			blk_finish_plug(plug);
 			cond_resched();