[PATCH v15 43/43] btrfs: zoned: deal with holes writing out tree-log pages

[Naohiro Aota <naohiro.aota@wdc.com>]

Since the zoned filesystem requires sequential write out of metadata, we
cannot proceed with a hole in tree-log pages. When such a hole exists,
btree_write_cache_pages() will return -EAGAIN. We cannot wait for the range
to be written, because it will cause a deadlock. So, let's bail out to a
full commit in this case.

Cc: Filipe Manana <fdmanana@gmail.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
---
 fs/btrfs/tree-log.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

This patch solves a regression introduced by fixing patch 40. I'm
sorry for the confusing patch numbering.

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 4e72794342c0..629e605cd62d 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -3120,6 +3120,14 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
 	 */
 	blk_start_plug(&plug);
 	ret = btrfs_write_marked_extents(fs_info, &log->dirty_log_pages, mark);
+	/*
+	 * There is a hole writing out the extents and cannot proceed it on
+	 * zoned filesystem, which require sequential writing. We can
+	 * ignore the error for now, since we don't wait for completion for
+	 * now.
+	 */
+	if (ret == -EAGAIN)
+		ret = 0;
 	if (ret) {
 		blk_finish_plug(&plug);
 		btrfs_abort_transaction(trans, ret);
@@ -3229,7 +3237,16 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
 					 &log_root_tree->dirty_log_pages,
 					 EXTENT_DIRTY | EXTENT_NEW);
 	blk_finish_plug(&plug);
-	if (ret) {
+	/*
+	 * There is a hole in the extents, and failed to sequential write
+	 * on zoned filesystem. We cannot wait for this write outs, sinc it
+	 * cause a deadlock. Bail out to the full commit, instead.
+	 */
+	if (ret == -EAGAIN) {
+		btrfs_wait_tree_log_extents(log, mark);
+		mutex_unlock(&log_root_tree->log_mutex);
+		goto out_wake_log_root;
+	} else if (ret) {
 		btrfs_set_log_full_commit(trans);
 		btrfs_abort_transaction(trans, ret);
 		mutex_unlock(&log_root_tree->log_mutex);
-- 
2.30.0