[PATCH v1 04/10] btrfs: add btrfs_try_lock_ordered_range

[Stefan Roesch <shr@fb.com>]

From: Josef Bacik <josef@toxicpanda.com>

For IOCB_NOWAIT we're going to want to use try lock on the extent lock,
and simply bail if there's an ordered extent in the range because the
only choice there is to wait for the ordered extent to complete.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Stefan Roesch <shr@fb.com>
---
 fs/btrfs/ordered-data.c | 28 ++++++++++++++++++++++++++++
 fs/btrfs/ordered-data.h |  1 +
 2 files changed, 29 insertions(+)

diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index 1952ac85222c..3cdfdcedb088 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -1041,6 +1041,34 @@ void btrfs_lock_and_flush_ordered_range(struct btrfs_inode *inode, u64 start,
 	}
 }
 
+/*
+ * btrfs_try_lock_ordered_range - lock the passed range and ensure all pending
+ * ordered extents in it are run to completion in nowait mode.
+ *
+ * @inode:        Inode whose ordered tree is to be searched
+ * @start:        Beginning of range to flush
+ * @end:          Last byte of range to lock
+ *
+ * This function returns 1 if btrfs_lock_ordered_range does not return any
+ * extents, otherwise 0.
+ */
+int btrfs_try_lock_ordered_range(struct btrfs_inode *inode, u64 start, u64 end)
+{
+	struct btrfs_ordered_extent *ordered;
+
+	if (!try_lock_extent(&inode->io_tree, start, end))
+		return 0;
+
+	ordered = btrfs_lookup_ordered_range(inode, start, end - start + 1);
+	if (!ordered)
+		return 1;
+
+	btrfs_put_ordered_extent(ordered);
+	unlock_extent(&inode->io_tree, start, end);
+	return 0;
+}
+
+
 static int clone_ordered_extent(struct btrfs_ordered_extent *ordered, u64 pos,
 				u64 len)
 {
diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h
index 87792f85e2c4..ec27ebf0af4b 100644
--- a/fs/btrfs/ordered-data.h
+++ b/fs/btrfs/ordered-data.h
@@ -218,6 +218,7 @@ void btrfs_wait_ordered_roots(struct btrfs_fs_info *fs_info, u64 nr,
 void btrfs_lock_and_flush_ordered_range(struct btrfs_inode *inode, u64 start,
 					u64 end,
 					struct extent_state **cached_state);
+int btrfs_try_lock_ordered_range(struct btrfs_inode *inode, u64 start, u64 end);
 int btrfs_split_ordered_extent(struct btrfs_ordered_extent *ordered, u64 pre,
 			       u64 post);
 int __init ordered_data_init(void);
-- 
2.30.2