btrfs: rename struct btrfs_io_bio to btrfs_bio

Previously we had "struct btrfs_bio", which records IO context for
mirrored IO and RAID56, and "strcut btrfs_io_bio", which records extra
btrfs specific info for logical bytenr bio.

With "btrfs_bio" renamed to "btrfs_io_context", we are safe to rename
"btrfs_io_bio" to "btrfs_bio" which is a more suitable name now.

The struct btrfs_bio changes meaning by this commit. There was a
suggested name like btrfs_logical_bio but it's a bit long and we'd
prefer to use a shorter name.

This could be a concern for backports to older kernels where the
different meaning could possibly cause confusion or bugs. Comparing the
new and old structures, there's no overlap among the struct members so a
build would break in case of incorrect backport.

We haven't had many backports to bio code anyway so this is more of a
theoretical cause of bugs and a matter of precaution but we'll need to
keep the semantic change in mind.

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, 14 insertions, 15 deletions

diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index b69755fc0e0d..83075d6855db 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -304,38 +304,37 @@ struct btrfs_fs_devices {
 				/ sizeof(struct btrfs_stripe) + 1)
 
 /*
- * we need the mirror number and stripe index to be passed around
- * the call chain while we are processing end_io (especially errors).
- * Really, what we need is a btrfs_io_context structure that has this info
- * and is properly sized with its stripe array, but we're not there
- * quite yet.  We have our own btrfs bioset, and all of the bios
- * we allocate are actually btrfs_io_bios.  We'll cram as much of
- * struct btrfs_io_context as we can into this over time.
+ * Additional info to pass along bio.
+ *
+ * Mostly for btrfs specific features like csum and mirror_num.
  */
-struct btrfs_io_bio {
+struct btrfs_bio {
 	unsigned int mirror_num;
+
+	/* @device is for stripe IO submission. */
 	struct btrfs_device *device;
 	u64 logical;
 	u8 *csum;
 	u8 csum_inline[BTRFS_BIO_INLINE_CSUM_SIZE];
 	struct bvec_iter iter;
+
 	/*
 	 * This member must come last, bio_alloc_bioset will allocate enough
-	 * bytes for entire btrfs_io_bio but relies on bio being last.
+	 * bytes for entire btrfs_bio but relies on bio being last.
 	 */
 	struct bio bio;
 };
 
-static inline struct btrfs_io_bio *btrfs_io_bio(struct bio *bio)
+static inline struct btrfs_bio *btrfs_bio(struct bio *bio)
 {
-	return container_of(bio, struct btrfs_io_bio, bio);
+	return container_of(bio, struct btrfs_bio, bio);
 }
 
-static inline void btrfs_io_bio_free_csum(struct btrfs_io_bio *io_bio)
+static inline void btrfs_bio_free_csum(struct btrfs_bio *bbio)
 {
-	if (io_bio->csum != io_bio->csum_inline) {
-		kfree(io_bio->csum);
-		io_bio->csum = NULL;
+	if (bbio->csum != bbio->csum_inline) {
+		kfree(bbio->csum);
+		bbio->csum = NULL;
 	}
 }