[PATCH 5/6] btrfs: use nocow_end for the loop iteration in run_delalloc_cow

[Christoph Hellwig <hch@lst.de>]

When run_delalloc_cow allocates an ordered extent for an actual
NOCOW range, it uses the nocow_end variable calculated based on
the current offset and the nocow_args.num_bytes value returned
from can_nocow_file_extent for all the actual I/O, but the loop
iteration then resets cur_offset to extent_end, which caused
me a lot of confusion.  It turns out that nocow_end is based
of the minimum of the extent end and the range end, and thus
actually works perfectly fine for the loop iteration, but
using a different variable here from the actual I/O submission
is horribly confusing and wasted some of my precious brain
cells when train to understand the logic.  Switch to using
nocow_end adjusted by the the off by one to make it an exclusive
range.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/btrfs/inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 92182e0d27fdb5..caaf2c002d795d 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2187,7 +2187,7 @@ static noinline int run_delalloc_nocow(struct btrfs_inode *inode,
 					     EXTENT_CLEAR_DATA_RESV,
 					     PAGE_UNLOCK | PAGE_SET_ORDERED);
 
-		cur_offset = extent_end;
+		cur_offset = nocow_end + 1;
 
 		/*
 		 * btrfs_reloc_clone_csums() error, now we're OK to call error
-- 
2.39.2