btrfs: rename bio_offset of extent_submit_bio_start_t to dio_file_offset

The parameter bio_offset of extent_submit_bio_start_t is very confusing.
If it's really bio_offset (offset to bio), then it should be u32.  But
in fact, it's only utilized by dio read, and that member is used as file
offset, which must be u64.

Rename it to dio_file_offset since the only user uses it as file offset,
and add comment for who is using it.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/disk-io.c

@@ -113,11 +113,9 @@ struct async_submit_bio {
 	struct bio *bio;
 	extent_submit_bio_start_t *submit_bio_start;
 	int mirror_num;
-	/*
-	 * bio_offset is optional, can be used if the pages in the bio
-	 * can't tell us where in the file the bio should go
-	 */
-	u64 bio_offset;
+
+	/* Optional parameter for submit_bio_start used by direct io */
+	u64 dio_file_offset;
 	struct btrfs_work work;
 	blk_status_t status;
 };
@@ -697,7 +695,8 @@ static void run_one_async_start(struct btrfs_work *work)
 	blk_status_t ret;
 
 	async = container_of(work, struct  async_submit_bio, work);
-	ret = async->submit_bio_start(async->inode, async->bio, async->bio_offset);
+	ret = async->submit_bio_start(async->inode, async->bio,
+				      async->dio_file_offset);
 	if (ret)
 		async->status = ret;
 }
@@ -749,7 +748,7 @@ static void run_one_async_free(struct btrfs_work *work)
 
 blk_status_t btrfs_wq_submit_bio(struct inode *inode, struct bio *bio,
 				 int mirror_num, unsigned long bio_flags,
-				 u64 bio_offset,
+				 u64 dio_file_offset,
 				 extent_submit_bio_start_t *submit_bio_start)
 {
 	struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info;
@@ -767,7 +766,7 @@ blk_status_t btrfs_wq_submit_bio(struct inode *inode, struct bio *bio,
 	btrfs_init_work(&async->work, run_one_async_start, run_one_async_done,
 			run_one_async_free);
 
-	async->bio_offset = bio_offset;
+	async->dio_file_offset = dio_file_offset;
 
 	async->status = 0;
 
@@ -797,7 +796,7 @@ static blk_status_t btree_csum_one_bio(struct bio *bio)
 }
 
 static blk_status_t btree_submit_bio_start(struct inode *inode, struct bio *bio,
-					   u64 bio_offset)
+					   u64 dio_file_offset)
 {
 	/*
 	 * when we're called for a write, we're already in the async

fs/btrfs/disk-io.h

@@ -116,7 +116,7 @@ blk_status_t btrfs_bio_wq_end_io(struct btrfs_fs_info *info, struct bio *bio,
 			enum btrfs_wq_endio_type metadata);
 blk_status_t btrfs_wq_submit_bio(struct inode *inode, struct bio *bio,
 				 int mirror_num, unsigned long bio_flags,
-				 u64 bio_offset,
+				 u64 dio_file_offset,
 				 extent_submit_bio_start_t *submit_bio_start);
 blk_status_t btrfs_submit_bio_done(void *private_data, struct bio *bio,
 			  int mirror_num);

fs/btrfs/extent_io.h

@@ -72,7 +72,7 @@ typedef blk_status_t (submit_bio_hook_t)(struct inode *inode, struct bio *bio,
 					 unsigned long bio_flags);
 
 typedef blk_status_t (extent_submit_bio_start_t)(struct inode *inode,
-		struct bio *bio, u64 bio_offset);
+		struct bio *bio, u64 dio_file_offset);
 
 #define INLINE_EXTENT_BUFFER_PAGES 16
 #define MAX_INLINE_EXTENT_BUFFER_SIZE (INLINE_EXTENT_BUFFER_PAGES * PAGE_SIZE)

fs/btrfs/inode.c

@@ -2212,7 +2212,7 @@ int btrfs_bio_fits_in_stripe(struct page *page, size_t size, struct bio *bio,
  * are inserted into the btree
  */
 static blk_status_t btrfs_submit_bio_start(struct inode *inode, struct bio *bio,
-					   u64 bio_offset)
+					   u64 dio_file_offset)
 {
 	return btrfs_csum_one_bio(BTRFS_I(inode), bio, 0, 0);
 }
@@ -7795,9 +7795,10 @@ static void __endio_write_update_ordered(struct btrfs_inode *inode,
 }
 
 static blk_status_t btrfs_submit_bio_start_direct_io(struct inode *inode,
-						     struct bio *bio, u64 offset)
+						     struct bio *bio,
+						     u64 dio_file_offset)
 {
-	return btrfs_csum_one_bio(BTRFS_I(inode), bio, offset, 1);
+	return btrfs_csum_one_bio(BTRFS_I(inode), bio, dio_file_offset, 1);
 }
 
 static void btrfs_end_dio_bio(struct bio *bio)
@@ -7846,8 +7847,7 @@ static inline blk_status_t btrfs_submit_dio_bio(struct bio *bio,
 		goto map;
 
 	if (write && async_submit) {
-		ret = btrfs_wq_submit_bio(inode, bio, 0, 0,
-					  file_offset,
+		ret = btrfs_wq_submit_bio(inode, bio, 0, 0, file_offset,
 					  btrfs_submit_bio_start_direct_io);
 		goto err;
 	} else if (write) {