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/extent_io.c b/fs/btrfs/extent_io.c
index f40e4a002f78..a1adadd5d25d 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -898,9 +898,10 @@ static void alloc_new_bio(struct btrfs_inode *inode,
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 	struct btrfs_bio *bbio;
 
-	bbio = btrfs_bio_alloc(BIO_MAX_VECS, bio_ctrl->opf, inode,
+	bbio = btrfs_bio_alloc(BIO_MAX_VECS, bio_ctrl->opf, fs_info,
 			       bio_ctrl->end_io_func, NULL);
 	bbio->bio.bi_iter.bi_sector = disk_bytenr >> SECTOR_SHIFT;
+	bbio->inode = inode;
 	bbio->file_offset = file_offset;
 	bio_ctrl->bbio = bbio;
 	bio_ctrl->len_to_oe_boundary = U32_MAX;