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, 16 insertions, 5 deletions

diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index d5d326c674b1..b4e6500548a2 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -199,8 +199,12 @@ static int __btrfs_add_ordered_extent(struct btrfs_inode *inode, u64 file_offset
 	entry->compress_type = compress_type;
 	entry->truncated_len = (u64)-1;
 	entry->qgroup_rsv = ret;
-	if (type != BTRFS_ORDERED_IO_DONE && type != BTRFS_ORDERED_COMPLETE)
-		set_bit(type, &entry->flags);
+
+	ASSERT(type == BTRFS_ORDERED_REGULAR ||
+	       type == BTRFS_ORDERED_NOCOW ||
+	       type == BTRFS_ORDERED_PREALLOC ||
+	       type == BTRFS_ORDERED_COMPRESSED);
+	set_bit(type, &entry->flags);
 
 	if (dio) {
 		percpu_counter_add_batch(&fs_info->dio_bytes, num_bytes,
@@ -256,6 +260,9 @@ int btrfs_add_ordered_extent(struct btrfs_inode *inode, u64 file_offset,
 			     u64 disk_bytenr, u64 num_bytes, u64 disk_num_bytes,
 			     int type)
 {
+	ASSERT(type == BTRFS_ORDERED_REGULAR ||
+	       type == BTRFS_ORDERED_NOCOW ||
+	       type == BTRFS_ORDERED_PREALLOC);
 	return __btrfs_add_ordered_extent(inode, file_offset, disk_bytenr,
 					  num_bytes, disk_num_bytes, type, 0,
 					  BTRFS_COMPRESS_NONE);
@@ -265,6 +272,9 @@ int btrfs_add_ordered_extent_dio(struct btrfs_inode *inode, u64 file_offset,
 				 u64 disk_bytenr, u64 num_bytes,
 				 u64 disk_num_bytes, int type)
 {
+	ASSERT(type == BTRFS_ORDERED_REGULAR ||
+	       type == BTRFS_ORDERED_NOCOW ||
+	       type == BTRFS_ORDERED_PREALLOC);
 	return __btrfs_add_ordered_extent(inode, file_offset, disk_bytenr,
 					  num_bytes, disk_num_bytes, type, 1,
 					  BTRFS_COMPRESS_NONE);
@@ -272,11 +282,12 @@ int btrfs_add_ordered_extent_dio(struct btrfs_inode *inode, u64 file_offset,
 
 int btrfs_add_ordered_extent_compress(struct btrfs_inode *inode, u64 file_offset,
 				      u64 disk_bytenr, u64 num_bytes,
-				      u64 disk_num_bytes, int type,
-				      int compress_type)
+				      u64 disk_num_bytes, int compress_type)
 {
+	ASSERT(compress_type != BTRFS_COMPRESS_NONE);
 	return __btrfs_add_ordered_extent(inode, file_offset, disk_bytenr,
-					  num_bytes, disk_num_bytes, type, 0,
+					  num_bytes, disk_num_bytes,
+					  BTRFS_ORDERED_COMPRESSED, 0,
 					  compress_type);
 }