btrfs: rework the order of btrfs_ordered_extent::flags

[BUG]
There is a long existing bug in the last parameter of
btrfs_add_ordered_extent(), in commit 771ed689d2cd ("Btrfs: Optimize
compressed writeback and reads") back to 2008.

In that ancient commit btrfs_add_ordered_extent() expects the @type
parameter to be one of the following:

- BTRFS_ORDERED_REGULAR
- BTRFS_ORDERED_NOCOW
- BTRFS_ORDERED_PREALLOC
- BTRFS_ORDERED_COMPRESSED

But we pass 0 in cow_file_range(), which means BTRFS_ORDERED_IO_DONE.

Ironically extra check in __btrfs_add_ordered_extent() won't set the bit
if we see (type == IO_DONE || type == IO_COMPLETE), and avoid any
obvious bug.

But this still leads to regular COW ordered extent having no bit to
indicate its type in various trace events, rendering REGULAR bit
useless.

[FIX]
Change the following aspects to avoid such problem:

- Reorder btrfs_ordered_extent::flags
  Now the type bits go first (REGULAR/NOCOW/PREALLCO/COMPRESSED), then
  DIRECT bit, finally extra status bits like IO_DONE/COMPLETE/IOERR.

- Add extra ASSERT() for btrfs_add_ordered_extent_*()

- Remove @type parameter for btrfs_add_ordered_extent_compress()
  As the only valid @type here is BTRFS_ORDERED_COMPRESSED.

- Remove the unnecessary special check for IO_DONE/COMPLETE in
  __btrfs_add_ordered_extent()
  This is just to make the code work, with extra ASSERT(), there are
  limited values can be passed in.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/include/trace/events/btrfs.h b/include/trace/events/btrfs.h
index ecd24c719de4..b9896fc06160 100644
--- a/include/trace/events/btrfs.h
+++ b/include/trace/events/btrfs.h
@@ -499,12 +499,13 @@ DEFINE_EVENT(
 
 #define show_ordered_flags(flags)					   \
 	__print_flags(flags, "|",					   \
-		{ (1 << BTRFS_ORDERED_IO_DONE), 	"IO_DONE" 	}, \
-		{ (1 << BTRFS_ORDERED_COMPLETE), 	"COMPLETE" 	}, \
+		{ (1 << BTRFS_ORDERED_REGULAR), 	"REGULAR" 	}, \
 		{ (1 << BTRFS_ORDERED_NOCOW), 		"NOCOW" 	}, \
-		{ (1 << BTRFS_ORDERED_COMPRESSED), 	"COMPRESSED" 	}, \
 		{ (1 << BTRFS_ORDERED_PREALLOC), 	"PREALLOC" 	}, \
+		{ (1 << BTRFS_ORDERED_COMPRESSED), 	"COMPRESSED" 	}, \
 		{ (1 << BTRFS_ORDERED_DIRECT),	 	"DIRECT" 	}, \
+		{ (1 << BTRFS_ORDERED_IO_DONE), 	"IO_DONE" 	}, \
+		{ (1 << BTRFS_ORDERED_COMPLETE), 	"COMPLETE" 	}, \
 		{ (1 << BTRFS_ORDERED_IOERR), 		"IOERR" 	}, \
 		{ (1 << BTRFS_ORDERED_TRUNCATED), 	"TRUNCATED"	})