btrfs: introduce btrfs_bio::fs_info member

Currently we're doing a lot of work for btrfs_bio:

- Checksum verification for data read bios
- Bio splits if it crosses stripe boundary
- Read repair for data read bios

However for the incoming scrub patches, we don't want this extra
functionality at all, just plain logical + mirror -> physical mapping
ability.

Thus here we do the following changes:

- Introduce btrfs_bio::fs_info
  This is for the new scrub specific btrfs_bio, which would not populate
  btrfs_bio::inode.
  Thus we need such new member to grab a fs_info

  This new member will always be populated.

- Replace @inode argument with @fs_info for btrfs_bio_init() and its
  caller
  Since @inode is no longer a mandatory member, replace it with
  @fs_info, and let involved users populate @inode.

- Skip checksum verification and generation if @bbio->inode is NULL

- Add extra ASSERT()s
  To make sure:

  * bbio->inode is properly set for involved read repair path
  * if @file_offset is set, bbio->inode is also populated

- Grab @fs_info from @bbio directly
  We can no longer go @bbio->inode->root->fs_info, as bbio->inode can be
  NULL. This involves:

  * btrfs_simple_end_io()
  * should_async_write()
  * btrfs_wq_submit_bio()
  * btrfs_use_zone_append()

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, 2 insertions, 1 deletions

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index d532a8c8c9d8..2d0493f0a184 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -69,7 +69,8 @@ static struct compressed_bio *alloc_compressed_bio(struct btrfs_inode *inode,
 
 	bbio = btrfs_bio(bio_alloc_bioset(NULL, BTRFS_MAX_COMPRESSED_PAGES, op,
 					  GFP_NOFS, &btrfs_compressed_bioset));
-	btrfs_bio_init(bbio, inode, end_io, NULL);
+	btrfs_bio_init(bbio, inode->root->fs_info, end_io, NULL);
+	bbio->inode = inode;
 	bbio->file_offset = start;
 	return to_compressed_bio(bbio);
 }